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Review Evolution of inflammatory bowel disease in Korea: a 60-year perspective on clinical and research development
Suk-Kyun Yang,orcid

DOI: https://doi.org/10.5217/ir.2025.00073
Published online: June 23, 2025

Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Correspondence to Suk-Kyun Yang, Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea. E-mail: sky@amc.seoul.kr
• Received: May 6, 2024   • Revised: May 22, 2025   • Accepted: June 2, 2025

© 2025 Korean Association for the Study of Intestinal Diseases.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  • Inflammatory bowel disease (IBD) was once considered rare in Korea, with the first reported case documented in 1961. Since then, its incidence and prevalence have increased markedly, accompanied by significant progress in clinical care and research. This narrative review traces the historical evolution of IBD in Korea, dividing the timeline into 4 periods: 1960–1979, 1980–1999, 2000–2019, and 2020–2039. For each period, major developments in the research environment and trends, diagnostic process, patient population and characteristics, and treatment are outlined. Over the past 6 decades, diagnostic and therapeutic approaches in Korea have advanced markedly, transitioning from limited diagnostic capacity and symptom-based management to practices that align with global standards. Notably, Korean patients with IBD exhibit distinctive clinical features compared with Western counterparts, including a markedly higher proportion of proctitis and a lower long-term risk of colectomy in ulcerative colitis, and a substantially higher prevalence of perianal fistulas in Crohn’s disease, highlighting the need for population-specific strategies to advance personalized medicine. In parallel, the research landscape has evolved through multicenter collaborations, expanded research capacity, and growing international engagement, positioning Korea as an increasingly active contributor to the global IBD research community. Looking ahead, the future of IBD research in Korea is expected to be shaped by innovation-driven research, including advances in artificial intelligence, large-scale data integration, and deeper international collaboration. By tracing the clinical and research trajectory of IBD in Korea, this review offers insight into how the country has adapted to global trends and is preparing to meet future challenges.
  • Keywords: Inflammatory bowel disease; Korea; History; Epidemiology
Inflammatory bowel disease (IBD) was previously considered a rare condition in Korea. However, over the past few decades, its incidence and prevalence have increased rapidly [1-9]. While the history of IBD in Western countries dates back approximately 250 years to the time of the Industrial Revolution [10], Korea’s experience with IBD began much more recently, with the first case report published in the early 1960s [11,12], marking a history of just over 60 years, which is roughly one quarter that of the West. According to the framework proposed by Kaplan and Windsor [10], the global evolution of IBD can be classified into 4 epidemiologic stages: Emergence, Acceleration in Incidence, Compounding Prevalence, and Prevalence Equilibrium. As of 2020, most Asian countries, including Korea, were classified as being in stage 2 (Acceleration in Incidence).
While several studies have documented trends in the incidence and prevalence [1-9], a comprehensive overview of the evolution of IBD in Korea, encompassing changes in disease recognition, clinical care, research, and infrastructure, remains lacking. To address this gap, this review provides a 60-year perspective on the clinical and research evolution of IBD in Korea, with a focus on (1) research environment and trends, (2) diagnostic process, (3) patient population and characteristics, and (4) treatment, while also offering insights into future directions.
Korean studies on IBD were retrieved using a dedicated search strategy. A “Korean study” was defined as a research article in which either the first or corresponding author was affiliated with a Korean institution and in which Korean data were used, or a review article in which either the first or corresponding author was affiliated with a Korean institution and which focused on IBD in Korea. Studies in which the first author was affiliated with a Korean institution but conducted during an overseas fellowship with a foreign corresponding author were not considered Korean studies. A PubMed search was conducted on February 10, 2025, to identify all Korean studies on IBD published from 1987 (the year of first indexation in PubMed) to December 31, 2024, using the following search query: (ulcerative colitis OR Crohn’s disease OR inflammatory bowel disease) AND Korea. Of the 3,126 articles retrieved, 73 were excluded for being either published in 2025 or only available as Epub in 2024. In addition, 283 articles unrelated to either ulcerative colitis (UC) or Crohn’s disease (CD), 307 that did not meet the Korean study criteria, and 1 retracted article were excluded, resulting in a final total of 2,462 articles. Among these, 1,719 were original articles, including 792 clinical research articles, while 387 were review articles, 214 were case reports, and 142 were other publications (Table 1). The review articles included 44 meta-analyses, 14 clinical guidelines, and 9 consensus statements.
As most Korean domestic journals published before 2000 were not indexed in PubMed, only a limited number of Korea-based IBD studies from this period were retrievable via PubMed searches. Therefore, the Korean Medical Database (KMBase) was searched using the aforementioned search query. As KMBase includes articles published since 1960, the search period was set from 1960 to 1999. Of the 320 articles retrieved, 102 that were unrelated to either UC or CD and 8 that had been duplicated in different journals were excluded. Consequently, 210 articles were included, comprising 96 case reports, 84 original articles, 28 review articles, 1 editorial, and 1 image article.
The retrieved articles, 2,462 from PubMed and 210 from KMBase, were analyzed to examine IBD research trends in Korea. Additionally, studies addressing the diagnostic process, patient population and characteristics, and treatment were analyzed to assess temporal changes in these aspects. As this review primarily focused on clinical research, basic and translational studies were not systematically reviewed, although brief mentions were included where relevant. To provide further context, key issues that may have influenced research trends in different periods were documented, even if not explicitly discussed in the retrieved articles. For the analysis, the study period was divided into four 20-year intervals: Period I (1960–1979), Period II (1980–1999), Period III (2000–2019), and Period IV (2020–2039). Period IV was described based on studies published up to 2024, with future prospects discussed for 2025 and beyond.
1. Research Environment and Trends
This period marks the beginning of IBD recognition in Korea, during which awareness of UC and CD remained very limited. The first reported cases of UC in Korea were published in 1961 by internists at Severance Hospital, who described 2 patients [11]. The first CD cases were reported a year later, in 1962, by surgeons at the same institution, who documented 8 patients [12]. Between 1960 and 1979, a total of 27 IBD-related articles were identified in KMBase. Among these, 17 (63.0%) were case reports, 6 (22.2%) were original articles, and 4 (14.8%) were review articles. All original articles were clinical studies, predominantly descriptive in nature, addressing the general clinical features of IBD rather than focusing on specific issues. No basic or translational research was conducted during this period. Notably, even this period’s largest clinical series were limited in size, with a report from Seoul National University Hospital including 28 patients with UC [13], and another from Severance Hospital including 27 patients with CD [14].
2. Diagnostic Process
In this period, the diagnosis of UC was primarily based on sigmoidoscopy and barium enema. In the largest clinical series from this period [13], which included 28 patients with UC, 25 patients underwent both sigmoidoscopy and barium enema, while 3 underwent only barium enema. In 6 case reports involving 11 patients with UC [11,15-19], 8 underwent both sigmoidoscopy and barium enema, 2 underwent only barium enema, and 1 was diagnosed postoperatively without any preoperative diagnostic evaluation. Although colonoscopy became available in Korea in the early 1970s, its application in UC diagnosis during this period appears limited. In 1975, Yoon [20] published a report on colonoscopy, in which 3 UC cases were identified among >100 patients who underwent the procedure. However, no UC-specific articles from this period mentioned colonoscopy as a diagnostic tool. On the other hand, given the high prevalence of amebic colitis at the time, stool testing for amoeba was routinely performed to rule it out [11,13,15-19].
As with UC, the diagnosis of CD during this period relied largely on barium enema. Among 49 patients diagnosed with CD [14,21-26 38], (77.6%) underwent barium enema prior to surgery, while colonoscopy, sigmoidoscopy, or small bowel imaging were not mentioned. As CD was still a relatively unfamiliar disease at the time, only 12 (24.5%) of the 49 patients were suspected or diagnosed with CD preoperatively, while 20 (40.8%) were misdiagnosed with colon cancer due to a palpable abdominal mass. In most cases, the diagnosis of CD was made postoperatively [14,21-26].
3. Patient Population and Characteristics
The KMBase search yielded 17 articles on UC published during this period. After excluding 4 review articles and 1 study that did not describe the clinical features of UC, 12 original articles or case reports remained, collectively including 47 patients [11,13,15-19,27-31]. However, given the limited awareness and clinical experience with UC at the time, several of these cases may have been misdiagnosed [32]. For instance, reported cases included patients with multiple ulcers at the site of colonic obstruction caused by colon cancer [27,28]; isolated descending colonic stricture with normal rectosigmoid mucosa [29]; acute-onset fever and abdominal pain, with a positive Widal test showing high antibody titers [30]; and ascending colon ulcers following antibiotic treatment for fever, chills, and upper abdominal pain [31]. To minimize the potential for diagnostic errors and duplicate reporting (e.g., multiple publications from the same institution), 5 articles reporting on 8 patients were excluded [27-31]. The remaining 7 articles describing 39 patients were included in the analysis [11,13,15-19].
Among these 39 patients with UC, the male-to-female ratio was 1.6:1, and the mean age at diagnosis was 36.0 years. In the largest clinical series conducted during this period [13], 18 (64.3%) of the 28 patients had disease limited to the rectum or rectosigmoid colon. However, this study did not distinguish between proctitis and proctosigmoiditis; so the exact number of patients with disease confined to the rectum remains unknown. In other case reports [11,15-19], none of the 11 patients had disease confined to the rectum; 4 had left-sided colitis and 7 had extensive colitis. These findings suggest that patients with milder symptoms and isolated proctitis were likely underdiagnosed during this period. Moreover, considering the limitations of the diagnostic methods used at the time, mainly sigmoidoscopy and barium enema, which may underestimate the true disease extent, the proportion of patients with extensive colitis among those diagnosed may have been even higher than that reported. Taken together, it appears that patients diagnosed during this period may have had more severe symptoms and a broader disease extent than those diagnosed in later decades.
Regarding CD, the KMBase search yielded 11 original articles or case reports published during this period, collectively including 94 patients. To minimize the potential for duplicate reporting, particularly from multiple publications originating from the same institution, 4 articles including 45 patients were excluded. Accordingly, the remaining 7 articles describing 49 patients were included in the analysis [14,21-26].
Among these 49 patients with CD, the male-to-female ratio was 1.5:1, which is consistent with studies published after 1980. However, the mean age at diagnosis was 38.0 years, markedly higher than that reported in the later decades. Notably, 31 patients (63.3%) had a palpable abdominal mass, and most of the 49 patients were diagnosed only after surgery. Collectively, these findings suggest that diagnosis was often delayed until the disease had progressed significantly. Regarding disease location, 15 patients (30.6%) had only small bowel involvement, 14 (28.6%) had only colonic involvement, and 20 (40.8%) had both small and large bowel involvement [14, 21-26]. This distribution differs somewhat from the patterns reported in the post-1980 literature.
4. Treatment
For UC, corticosteroids were the most commonly used medical treatment during this period, being administered to most of the 39 analyzed patients (although the exact number was not specified) [11,13,15-19], whereas sulfasalazine was used in only 3 patients [19]. This is noteworthy given that, in current practice, 5-aminosalicylic acid (5-ASA) agents such as sulfasalazine are typically the first-line therapy for UC, with corticosteroids reserved for patients with moderate to severe disease or those who do not respond to 5-ASA. This treatment pattern, characterized by the limited use of sulfasalazine and broader application of corticosteroids, may reflect limited awareness of UC management strategies, limited availability of 5-ASA, and/or a tendency to diagnose more severe cases, although this cannot be determined with certainty. Surgery was performed in 6 patients with UC, but all procedures were limited resections that preserved the rectum, including subtotal colectomy with ileosigmoidostomy or ileostomy and segmental colectomy such as left hemicolectomy with colosigmoidostomy [11,13,18]. This pattern suggests a lack of established surgical standards for UC in Korea at the time, with a focus on symptom control rather than curative resection.
Regarding CD, medical treatment was not described in any of the analyzed studies, likely reflecting both the unfamiliarity with CD and the lack of established treatment protocols in Korea during this period. Instead, all 49 reported patients underwent surgical treatment, typically in the context of an abdominal mass or suspected malignancy [14,21-26]. At that time, the limited clinical awareness of CD and the difficulty of making a definitive preoperative diagnosis often led to surgical intervention serving both diagnostic and therapeutic purposes.
1. Research Environment and Trends
Compared with the preceding period, the 1980–1999 era marked a notable shift in the recognition and investigation of IBD in Korea. During these two decades, growing clinical interest, modest advances in diagnostic tools, and the gradual accumulation of experience contributed to a growing volume of domestic research. Consequently, the KMBase search yielded 183 articles on IBD. Of these, 79 (43.2%) were case reports, 78 (42.6%) were original articles, 24 (13.1%) were review articles, and 2 (1.1%) were other articles, reflecting a relative decrease in the proportion of case reports and an increase in original research. This represented a 7-fold increase in total publications and a 13-fold increase in original research articles compared with those in the previous two decades.
Clinical studies from this period exhibited several notable developments compared with previous studies. First, study populations became larger, with some studies including >100 patients [33-36]. Second, researchers began to examine not only cross-sectional clinical characteristics but also the longitudinal disease course [33,36-38]. Third, rather than merely describing general clinical features, some studies focused on specific issues, such as procedure-specific surgical outcomes in UC [39], or perianal disease-related clinical outcomes in CD [38]. Representative studies from this period include those by Chang et al. [33], which analyzed 240 patients with UC, and by Song et al. [36], which analyzed 117 patients with CD.
In addition, the first basic science study related to IBD was published in 1992, marking the beginning of laboratory-based research in the field [40]. Furthermore, case reports published during this period began to focus more on cases of IBD with rare or complex comorbidities, such as primary sclerosing cholangitis [41], autoimmune hemolytic anemia [42], or cerebral venous sinus thrombosis [43]. Notably, in the latter half of this period, IBD research from Korea was first published in non-Korean international journals indexed in PubMed, including 4 clinical studies [44-47], 3 basic laboratory experiments [48-50], and 2 case reports [51,52]. This milestone marked the first international recognition of IBD research from Korea. In 1997, Suk-Kyun Yang of Asan Medical Center (University of Ulsan) established the Songpa-Kangdong IBD (SK-IBD) Research Group, the first organized research team dedicated to IBD in Korea [1]. This group initiated population-based studies in the Songpa-Kangdong district of Seoul, with publications appearing in the 2000s and beyond [1-3,53-56].
2. Diagnostic Process
During this period, colonoscopy emerged as the predominant diagnostic tool for UC in Korea, marking a dramatic shift from the reliance on sigmoidoscopy or barium enema in the preceding two decades. Among the 20 studies published between 1980 and 1999 that described the general clinical features of UC in cohorts of >10 patients, 8 were excluded to avoid the risk of overlapping patient cases reported by the same institution. Of the remaining 12 studies [33,34,37,57-65], only 5 explicitly described the diagnostic methods used [57-61]. In these 5 studies [57-61], colonoscopy was the primary diagnostic tool, performed in 181 of 185 patients (97.8%). However, barium enema was still performed in 140 patients (75.7%), suggesting that this period represented a transitional phase, during which colonoscopy had not yet fully replaced older modalities [57-61].
In contrast to UC, the diagnostic process for CD during this period remained relatively underdeveloped. Among the 13 studies describing the general clinical features of CD in cohorts of >10 patients, 6 were excluded because the study populations may have partially overlapped with those of other reports from the same institution. None of the remaining 7 studies provided detailed information on diagnostic methods [36,66-71]. However, one of the excluded studies, by Lee et al. [72], reported on the preoperative diagnostic workup in 42 surgically treated CD patients between 1978 and 1997. In this study, barium enema was performed in 32 patients, small bowel follow-through in 27, colonoscopy in 19, and abdominal computed tomography (CT) in 5. While these findings suggest a clear improvement in diagnostic tools compared with those in the pre-1980 period, when barium enema was virtually the only modality used, the overall diagnostic approach still appears to have been suboptimal. Notably, only 11 (26.2%) of the 42 patients had been diagnosed with or were suspected to have CD prior to surgery. Two factors may explain this low rate of preoperative diagnosis. First, 20 (47.6%) of the 42 patients underwent surgery for bowel obstruction, suggesting that many patients may have required urgent surgery before adequate diagnostic evaluation could be performed. Second, limited clinical experience and low awareness of CD during this period may also have contributed to the low preoperative diagnosis rate.
Reported time intervals from symptom onset to UC diagnosis varied considerably across studies. In one study [57], 29 of 37 patients (78.4%) were diagnosed within 1 month, whereas, in another study [73], only 12 of 39 patients (30.8%) were diagnosed within 1 year. Because of differences in the time intervals used across studies, direct comparison of diagnostic delays was limited. Nonetheless, in the 4 studies that reported the proportion of patients diagnosed within 6 months, the rates ranged from 31.6% to 54.2% [58-61]. Although not published during the 1980–1999 period, a population-based SK-IBD study published in 2020 by Cha et al. [53] analyzed 152 patients diagnosed with UC between 1986 and 1999 and reported a median diagnostic interval of 5.9 months. In a hospital-based study, Son et al. [74] investigated the initial diagnoses assigned to UC patients at their first healthcare visit. Only 47 of 150 patients (31.3%) were correctly diagnosed with UC at first presentation, while the remainder were commonly misdiagnosed with hemorrhoids (n=25, 16.7%), dysentery (n=13, 8.7%), or irritable bowel syndrome (n=14, 9.3%) [74].
As for CD, the interval from symptom onset to diagnosis during this period was reported in only one hospital-based study conducted at Seoul National University Hospital, with a mean of 29 months [36]. A later hospital-based study from Asan Medical Center, published in 2014 [75], which analyzed a cohort of 2,043 patients with CD diagnosed between 1981 and 2012, reported a median diagnostic delay of 24 months in 363 patients diagnosed between 1981 and 2000. These findings indicate that the time to diagnosis for CD was considerably longer than for UC. In Korea, intestinal tuberculosis (TB) has historically been a key differential diagnosis in suspected CD cases. Because intestinal TB was more prevalent than CD during this period, empirical anti-TB therapy was commonly administered when the diagnosis was unclear. Notably, 42%–45% of patients with CD were treated with anti-TB therapy before being definitively diagnosed with CD [32]. In 2 surgical case series, the preoperative diagnosis was intestinal TB in 29.6% (8 of 27) [66] and 50.0% (5 of 10) [69] of patients eventually diagnosed with CD.
3. Patient Population and Characteristics
According to a population-based SK-IBD study by Park et al. [1], the age- and sex-adjusted mean annual incidence rates in the Songpa-Kangdong district of Seoul increased significantly from 0.29 to 1.84 per 100,000 between 1986–1990 and 1996–2000 for UC, and from 0.06 to 0.44 per 100,000 during the same period for CD (Fig. 1).
Among the 791 patients with UC in the 12 analyzed studies, the male-to-female ratio was 1:1.3, indicating a slight female predominance [33,34,37,57-65]. This contrasts with the male predominance (1.6:1) observed in the previous period [3,13,15-19]. In the 6 studies that reported age at diagnosis [33,34,57,61-63], the mean age ranged from the late 30s to early 40s, with a pooled mean of 37.6 years, comparable with the prior period. Among the 232 patients with CD in the 7 analyzed studies [36,66-71], the male-to-female ratio was 1.7:1, similar to the earlier era. Regarding age at diagnosis, the largest study (n=117), conducted by Song et al. [36] at Seoul National University Hospital, reported a mean age of 22 years, which was substantially younger than that in the previous period. Of the remaining 6 small-scale studies, 4 reported mean age at diagnosis with a pooled average of 35.9 years [66-69], similar to that in the previous period, while the other 2 were not directly comparable due to reporting only age distributions [70,71]. In this context, the younger age reported by Song et al. [36], based on a larger cohort, may have been an early indicator of a shift toward earlier onset, which became more apparent in subsequent decades.
In terms of disease extent in UC, among the 791 patients analyzed, 213 (26.9%) had proctitis, 337 (42.6%) had left-sided colitis, 207 (26.2%) had extensive colitis, and 24 (3.0%) had atypical distributions, while in 10 (1.3%) patients, the disease extent was unknown [33,34,37,57-65]. Compared with the previous period, the increased proportion of proctitis cases in this period suggests a more frequent diagnosis of milder disease forms. Regarding CD, disease location was reported for 232 patients: 69 (29.7%) had only small bowel involvement, 53 (22.8%) had only colonic involvement, and 110 (47.4%) had both small and large bowel involvement [36,66-71]. This pattern suggests a trend toward decreased isolated colonic involvement and increased combined small and large bowel involvement compared with the earlier period.
Perianal disease is frequently observed in Korean patients with CD. In a study by Chang et al. [38], 52 of 117 patients (44.4%) diagnosed with CD at Seoul National University Hospital between 1975 and 1996 had perianal lesions. Similarly, a 2019 population-based SK-IBD study by Park et al. [1] found that 24 of 58 CD patients (41.4%) diagnosed between 1986 and 2000 had a perianal fistula or abscess before or at CD diagnosis.
4. Treatment
During this period, corticosteroids and sulfasalazine were the most commonly used medical therapies for UC in Korea. At Seoul National University Hospital, corticosteroids were used in 113 (92.6%) of 122 patients [35], while at Ewha Womans University Hospital, all 59 patients (100%) received corticosteroids [58]. In contrast, at Asan Medical Center, only 24 (36.3%) of 66 patients received corticosteroids [37], highlighting substantial variation in treatment practices across institutions. Compared with the previous period, sulfasalazine was widely used [35,37,61], and mesalazine began to be introduced as an alternative in the early 1990s [62]. Thiopurines were rarely used, with only 2 cases reported [35,76], suggesting their limited use in UC management during this period. Regarding surgical treatment, only 1 study from this period, conducted at Seoul National University Hospital [33], reported the cumulative risks of colectomy: 5.0% at 1 year, 7.6% at 2 years, 10.2% at 3 years, and 15.9% at 6 years.
Surgical indications were assessed in 5 studies, each reporting ≥5 colectomy cases [37,39,63,64,76]. Among the 57 patients described, perforation accounted for 12.3% (7 patients) of surgical indications, which was considerably high [37,39,63,64,76]. However, findings from 2 separate studies, conducted at Seoul National University Hospital, demonstrated a decline in perforation-related surgeries over time: 40.0% (2 of 5 patients) in 1976–1985 [73] and 10.3% (3 of 29 patients) in 1980–1996 [39]. This trend suggests that as clinical experience accumulated, surgeries were increasingly performed before the development of severe complications.
Total proctocolectomy (TPC) with ileal pouch-anal anastomosis (IPAA) was first reported in Korea in 1984 [77]. However, its adoption remained limited for nearly a decade. At Seoul National University Hospital, the leading center for UC surgery during this period, IPAA was not introduced until 1993; of the 29 surgeries performed between 1980 and 1996, IPAA was employed in 14 cases [39]. Jung et al. [78] also reported 5 cases of IPAA performed between 1990 and 1996. Collectively, these findings suggest that TPC with IPAA gradually gained acceptance as the standard surgical approach for UC in Korea during the 1990s.
Additional insight was provided by the 1986–1999 cohort of a population-based SK-IBD study by Cha et al. [53], published in 2020. All 152 patients with UC in this subgroup received 5-ASA during their disease course, consistent with Western treatment patterns. The cumulative risks of commencing corticosteroids were 33.6% at 1 year and 50.9% at 5 years, whereas the cumulative risks of commencing thiopurines remained low (0.0% at 1 year and 2.8% at 5 years) [53]. The cumulative risks of colectomy were 4.6% at both 1 and 5 years, lower than those reported in a single-center study from Seoul National University Hospital [33] over a comparable period, but still higher than those observed in the cohort diagnosed after 2000 in the same SK-IBD study [53].
Medical treatment of CD was addressed in only 3 studies from Seoul National University Hospital published during this period [36,72,79]. In an adult gastroenterology study [36], specific drug usage rates were not provided; however, corticosteroids were described as the primary treatment, with sulfasalazine or azathioprine added depending on the clinical context. In a pediatric study including 12 patients [79], corticosteroids were used in 10 and sulfasalazine in 9, which again highlights the central role of corticosteroids in CD treatment during this period. A study from the surgical department [72] described 42 patients who underwent bowel resection, among whom 27 (64%) received postoperative medical therapy; of these, corticosteroids were administered in 24 patients, azathioprine in 21, and sulfasalazine in 19. These findings suggest that thiopurines were prescribed in a substantial number of patients for postoperative maintenance therapy during this period, although corticosteroids remained widely used even after surgery. Regarding surgical treatment, only 1 study, conducted at Seoul National University Hospital [36], reported the cumulative risks of intestinal resection: 20% at 1 year, 23% at 2 years, 38% at 4 years, 45% at 6 years, and 62% at 10 years.
In contrast to UC, no population-based study has analyzed the cumulative risks of commencing medications among patients with CD diagnosed exclusively before 2000. However, approximate estimates can be inferred from a population-based SK-IBD study by Ye et al. [55], published in 2022, which separately analyzed a subgroup of 110 patients diagnosed with CD between 1986 and 2003. Despite including some patients diagnosed between 2000 and 2003, this study still provides valuable insights into treatment patterns during the pre-2000 period. In this subgroup, the cumulative risks of commencing corticosteroids were 45.5% at 1 year and 62.6% at 5 years. Given the steady decline in corticosteroid use over time, the actual cumulative rates among patients diagnosed exclusively before 2000 could be even higher than the rates observed in the 1986–2003 cohort. In the same study, the cumulative risks of commencing thiopurines were 16.4% at 1 year and 43.3% at 5 years [55]. In comparison, a hospital-based study from Asan Medical Center, published in 2014, analyzed a subgroup of 363 patients diagnosed with CD between 1981 and 2000 and reported even lower cumulative risks of commencing thiopurines, 5.0% at 1 year and 28.9% at 5 years, despite its hospital-based setting [75]. This discrepancy reflects a possible rapid increase in thiopurine adoption from the late 1990s to the early 2000s. Therefore, had the SK-IBD study [55] restricted its analysis to patients diagnosed exclusively before 2000, the cumulative risk of commencing thiopurines in the SK-IBD cohort would likely have been considerably lower. As for surgical outcomes, the 1986–2003 cohort of the SK-IBD study by Ye et al. [55] reported cumulative risks of intestinal resection of 16.4% at 1 year and 20.1% at 5 years. However, had the analysis been limited to patients diagnosed before 2000, the resection rates would likely have been higher than these figures.
1. Research Environment and Trends
Beginning in the early 2000s, a sharp rise in the incidence of UC and CD spurred both clinical and academic interest in IBD, marking the beginning of a phase of rapid research expansion in Korea (Fig. 2). The volume and quality of IBD research in Korea grew markedly during this period. Between 2000 and 2019, a total of 1,355 IBD-related articles from Korea were indexed in PubMed. Of these, 899 (66.3%) were original articles, 217 (16.0%) were review articles, 163 (12.0%) were case reports, and 76 (5.6%) were other publications (Table 1). Although a direct comparison is limited by differences in database coverage, KMBase for 1980–1999 and PubMed for 2000–2019, the available data suggest a notable increase in research activity. Compared with the previous two decades (1980–1999), the total number of publications increased approximately 7-fold, and the number of original research articles increased 12-fold.
One of the most pivotal developments during this period was the establishment of the Korean Association for the Study of Intestinal Diseases (KASID) in 2002, with Professor Kyu Yong Choi of The Catholic University of Korea serving as its first president. In 2003, KASID launched its official journal, Intestinal Research, which became the official journal of the Asian Organization for Crohn’s and Colitis (AOCC) in 2016. The establishment of KASID and the launch of Intestinal Research provided a formal collaborative platform for IBD specialists in Korea, enabling them to convene regularly, share knowledge, and disseminate their research, thereby facilitating academic communication and promoting cooperative research in the field of IBD.
From its inception, KASID has actively pursued international academic collaboration. Its second president, Professor Jin-Ho Kim of Asan Medical Center, collaborated with Professor Toshifumi Hibi of Japan to establish an annual Japan-Korea IBD Symposium, with the inaugural meeting held in Seoul in 2006. This symposium contributed to advancing IBD research in both countries and laid the foundation for the eventual establishment of the AOCC. The AOCC was initially proposed in 2012 by Professor Hyo Jong Kim of Kyung Hee University, who was then serving as the fifth president of KASID. The founding governing board included Toshifumi Hibi, Mamoru Watanabe, and Yasuo Suzuki from Japan; Pin Jin Hu, Jia Ming Qian, and Bing Xia from China; and Hyo Jong Kim, Suk-Kyun Yang, and Dong Soo Han from Korea. Professor Hibi was elected as the inaugural president, and the first AOCC annual meeting was held in Japan in 2013. The AOCC established a vital platform for academic collaboration across Asia, fostering deeper engagement between Korean researchers and their international peers.
KASID has also played a leading role in promoting multicenter collaborative research. Professor Suk-Kyun Yang of Asan Medical Center, the first chair of the KASID Scientific Committee (and later the sixth president of KASID), strongly advocated for multicenter studies. As a result of this initiative, the first multicenter collaborative study initiated by the KASID IBD Research Group was published in 2005 [80]. Following this initial success, the group continued to publish numerous multicenter studies, fostering a new research culture centered on inter-institutional collaboration. In 2008, Professor Won Ho Kim of Yonsei University, the third president of KASID, launched the “Research Network for Crohn’s Disease,” a national research project that focused on collecting clinical data and blood specimens from multiple institutions. This project was subsequently led by Professor Dong Soo Han of Hanyang University, followed by Professor Joo Sung Kim of Seoul National University. As systematic data collection expanded and research infrastructure matured, the project evolved into the Crohn’s Disease Clinical Network and Cohort (CONNECT), jointly developed with the KASID IBD Research Group [81]. In 2013, under the leadership of Professor Hyo Jong Kim, a new nationwide prospective hospital-based cohort for UC was launched. A working group of 12 KASID members developed the study protocol, and the cohort was named MOSAIK (Moderate-to-Severe Ulcerative Colitis in Korea) [82]. By the end of 2019, a total of 34 multicenter collaborative studies had been published under the leadership of the KASID IBD Research Group: 11 studies were based on CONNECT data, while studies based on the MOSAIK cohort began to be published starting in 2020 (Supplementary Table 1). Multicenter research was actively promoted at the regional level as well. Among KASID’s regional chapters, the Daegu-Gyeongbuk chapter was particularly active. In 2015, the group was formally named the Crohn’s and Colitis Association in Daegu-Gyeongbuk (CCAiD). Following this, Professor Eun Soo Kim of Kyungpook National University played a key role in leading and publishing CCAiD-led multicenter studies. Including earlier publications under its previous name, the Daegu-Gyeongbuk Gastrointestinal Study Group (DGSG), a total of 13 multicenter studies were produced by this group [82-95]. In addition to KASID-led initiatives, multicenter research efforts were also independently conducted by individual investigators. For example, Professor Dong Il Park of Kangbuk Samsung Hospital in Seoul led 11 additional multicenter collaborative studies [96-106]. He also established the IMPACT cohort (Identification of the Mechanism of the Occurrence and Progression of Crohn’s Disease), which focused on integrated genetic and environmental analyses and led to several multicenter publications beginning in 2020 [107]. As a result of these coordinated efforts, the number of multicenter clinical research articles rose substantially during 2000–2019, with 112 (27.6%) of the 406 clinical research articles involving multicenter collaborations.
As part of its ongoing collaborative efforts, KASID organized a “Dream Team” in 2012 to secure national research funding and further strengthen research infrastructure. Professor Suk-Kyun Yang of Asan Medical Center served as the principal investigator and led Subproject 1. The other Subproject leaders were Professor Jae Hee Cheon of Yonsei University (Subproject 2), Professor Dong Soo Han of Hanyang University (Subproject 3), Professor Young-Ho Kim of Samsung Medical Center (Subproject 4), and Dr. Kwang-Won Seo of Kang Stem Holdings (Subproject 5). This team successfully obtained a research grant from the Korean Health Technology R&D Project, Ministry of Health & Welfare, and conducted the project between 2012 and 2018 [108].
Alongside the expansion of research infrastructure and multicenter collaboration, the research focus has evolved from descriptive epidemiology to the investigation of genetic and clinical differences between Korean and Western patients. A representative example is the discovery that thiopurine-induced leukopenia is predominantly caused by NUDT15 variants in East Asian populations, including Koreans [108], whereas TPMT mutations are more commonly implicated in Western populations. This finding not only revealed a distinct pharmacogenetic trait of East Asians but also had direct clinical implications for personalized medicine. This finding was later incorporated into both domestic and international clinical guidelines, including those issued by the KASID [109], the AOCC [110], the British Society of Gastroenterology [111], and the Clinical Pharmacogenetics Implementation Consortium (CPIC) [112].
Another major development during this period was the emergence of population-based studies, indicating the broadening scope of clinical research in Korea. The first population-based study on IBD in Korea was published in 2000 by the SK-IBD Research Group, reporting the incidence and prevalence of UC in the Songpa-Kangdong district of Seoul between 1986 and 1997 [2]. While this landmark study provided important early insights from a localized setting, the use of nationwide claims data began to gain traction in the later years of this period. In 2015, Professor Hyun Jung Kim of Korea University published the first nationwide population-based study on IBD incidence and natural history using data from the Health Insurance Review and Assessment Service (HIRA), covering the years 2006–2012 [4]. Between 2015 and 2019, a total of 33 studies based on HIRA data were published (Supplementary Table 2).
In the latter half of this period, Korean researchers began to participate more actively in international clinical IBD research. In 2019, a landmark international, randomized, double-blind, phase 3 trial comparing the efficacy and safety of the biosimilar CT-P13 with the originator infliximab in patients with active CD was published in The Lancet [113]. This study represented the first large-scale, multinational clinical IBD trial led by Korean investigators, with Professors Byong Duk Ye and Young-Ho Kim serving as the first and corresponding authors, respectively. While earlier collaborations had been largely confined to regional networks such as the AOCC, this study marked a significant milestone in Korea’s expanding involvement in multinational clinical IBD research beyond Asia.
During the same period, the increasing burden of IBD prompted the establishment of dedicated IBD centers, beginning with Asan Medical Center in 2012 and subsequently expanding to other major hospitals. These centers played a key role in improving patient care, facilitating systematic data collection, and enhancing the research infrastructure.
In summary, the 2000–2019 period was characterized by rapid growth in research output, the adoption of high-quality multicenter and population-based study designs, and expanding institutional and international research networks. Collectively, these developments laid the academic, organizational, and infrastructural foundation for the next phase of innovation in Korean IBD research.
2. Diagnostic Process
According to a population-based SK-IBD study by Park et al. [1], several trends in the diagnostic practices for UC and CD were observed during this period. Colonoscopy remained the mainstay for UC diagnosis, with its use increasing further after 2000. The proportion of patients who underwent colonoscopy for UC diagnosis significantly increased from 87.0% in 1986–2005 to 99.4% in 2006–2015. In the diagnosis of CD, the most commonly used modality for small bowel evaluation shifted over time. Among patients diagnosed in 1986–2005, small bowel follow-through was performed in 79.8%, whereas in 2006–2015, CT or magnetic resonance (MR) enterography became the predominant modality, being performed in 70.9% of patients. In addition, capsule endoscopy and double-balloon enteroscopy became available in the early 2000s. Among 360 patients diagnosed with CD between 2001 and 2015, capsule endoscopy and double-balloon enteroscopy were performed in 46 patients (12.8%) and 8 patients (2.2%), respectively, indicating the limited, albeit increasing, adoption of advanced endoscopic techniques during this period.
Patterns of misdiagnosis in patients initially diagnosed with UC or CD revealed ongoing diagnostic challenges, particularly in differentiating CD from intestinal TB. Lee et al. [114] investigated the final diagnosis of 2,896 patients referred to Asan Medical Center after being diagnosed with UC or CD between 2010 and 2014. Among the 1,444 patients referred with a diagnosis of UC, 1,287 (89.1%) were ultimately confirmed to have UC. Of the remaining 157 patients, 108 were determined not to have IBD, with acute self-limited colitis being the most common misdiagnosis (n=66). Similarly, among the 1,452 patients referred with a diagnosis of CD, 1,209 (83.3%) were ultimately confirmed to have CD. Of the remaining 243 patients, 184 were determined not to have IBD, with acute self-limited colitis (n=57) and intestinal TB (n=53) being the most frequent misdiagnoses. With the increasing incidence of CD and the decreasing incidence of TB in Korea, the pattern of misdiagnosis also changed over time. According to a retrospective analysis of 2,760 patients with CD and 772 patients with intestinal TB managed at Asan Medical Center between 1996 and 2014 [115], 33.2% of patients ultimately diagnosed with CD were initially misdiagnosed or provisionally diagnosed with intestinal TB, leading to empirical anti-TB therapy in 1996–2000. However, this rate markedly declined to 9.9% in 2010–2014. In contrast, only 3.0% of patients ultimately diagnosed with intestinal TB were initially misdiagnosed as CD in 1996–2000, whereas this rate increased to 13.1% in 2010–2014.
Population-based studies during this period demonstrated a decreasing trend in time to diagnosis, particularly in CD [53,55]. In a population-based SK-IBD study by Cha et al. [53], the median interval from symptom onset to diagnosis in patients with UC showed a decreasing trend over time: 5.9 months in the 1986–1999 cohort (n=152), 2.6 months in the 2000–2009 cohort (n=445), and 2.4 months in the 2009–2015 cohort (n=416). Similarly, a population-based SK-IBD study by Ye et al. [55] reported a reduction in diagnostic delay among patients with CD, with the median interval decreasing from 14.8 months in the 1986–2003 cohort (n=110) to 8.9 months in the 2004–2015 cohort (n=308). These findings likely reflect improvements in diagnostic awareness and healthcare infrastructure, including greater patient accessibility, in Korea during this period.
3. Patient Population and Characteristics
According to a population-based SK-IBD study by Park et al. [1], the age- and sex-adjusted mean annual incidence rate in the Songpa-Kangdong district of Seoul significantly increased from 1.84 per 100,000 in 1996–2000 to 5.82 per 100,000 in 2011–2015 for UC, and from 0.44 per 100,000 to 2.44 per 100,000 over the same period for CD (Fig. 1). However, the average annual percentage change in IBD incidence, which had remained at 12.3% in both 1986–1995 and 1996–2005, slowed to 3.3% in 2006–2015, indicating a gradual deceleration in the rate of increase. Consistent with these regional findings, a nationwide population-based cohort study using the HIRA claims database by Kim et al. [8] reported that, in 2018, the incidence of UC and CD reached 8.21 and 3.33 per 100,000, respectively. They further noted that the incidence of UC continued to rise between 2010 and 2018, whereas the incidence of CD plateaued after 2014.
The prevalence of UC and CD in 2015 was 76.66 and 31.59 per 100,000, respectively, according to the population-based SK-IBD study by Park et al. [1]. This represented approximately a 2.5-fold increase compared with 2005, as reported in a previous population-based SK-IBD study by Yang et al. [3]. Similarly, in the nationwide population-based study by Kim et al. [8], the prevalence of UC and CD in 2018 was 65.5 and 32.7 per 100,000, respectively, approximately double the figures reported in 2010 for both diseases. These findings suggest that the prevalence doubling time in Korea is <10 years, which is considerably shorter than the estimated 20–25 years in Western countries [10]. The relatively rapid doubling of prevalence may reflect Korea’s current position within the global epidemiological transition of IBD. According to the model proposed by Kaplan and Windsor [10], Korea appears to be in the late phase of stage 2 (“acceleration in incidence”), characterized by a slowing increase in incidence but continued rapid growth in prevalence.
The male-to-female ratio of incidence was 1.2:1 for UC and 3.3:1 for CD among patients diagnosed between 1986 and 2015 in the population-based SK-IBD study by Park et al. [1]. A similar pattern was observed in the nationwide population-based study by Kim et al. [8], in which the ratio was 1.4:1 for UC and 2.6:1 for CD among patients diagnosed between 2005 and 2016. In contrast, European studies have reported that the incidence of CD is higher in males during childhood but becomes higher in females after adolescence [116]. By comparison, Korean data have consistently shown a male predominance throughout all age groups, indicating a distinct epidemiological pattern.
The median age at diagnosis was 36 years for UC and 22 years for CD among patients diagnosed between 1986 and 2015 in the population-based SK-IBD study by Park et al. [1], and 40 years for UC and 25 years for CD among patients diagnosed between 2005 and 2016 in the nationwide population-based study by Kim et al. [8]. These findings indicate that, in Korea, both UC and CD predominantly affect young individuals, consistent with patterns observed in Western countries. However, UC tends to present approximately 15 years later than CD. In comparison, the age difference at onset between UC and CD has been reported to be approximately 5–10 years in Europe [116], suggesting that the age gap between the two diseases may be more pronounced in Korea.
The disease extent at diagnosis in UC, as reported in the population-based SK-IBD study by Park et al. [1], was proctitis in 485 patients (57.9%), left-sided colitis in 169 (20.2%), and extensive colitis in 184 (21.9%) among 838 patients diagnosed between 2001 and 2015. Notably, in the same study, among those diagnosed between 1986 and 2000, the proportion of proctitis was only 37.1%, indicating a substantial increase over time. In contrast, studies from Europe have reported that the proportion of proctitis at diagnosis is approximately 27%–32% [116], suggesting that a higher proportion of proctitis may be a distinguishing feature of UC in Korea.
In the same study by Park et al. [1], the disease location at diagnosis in CD was ileal in 95 patients (26.4%), colonic in 30 (8.3%), and ileocolonic in 235 (65.3%) among 360 patients diagnosed between 2001 and 2015. This distribution differs markedly from that reported in European studies, where approximately 15%–38% of patients present with ileal disease, 24%–65% with colonic disease, and 10%–45% with ileocolonic disease [116]. Notably, the proportion of isolated colonic disease appears to be substantially lower in Korean patients than in European populations. Furthermore, Park et al. [1] reported that 87 patients (24.2%) had upper gastrointestinal (UGI) involvement, suggesting that UGI modifiers may be more common in Korean patients than in Western cohorts.
As for perianal fistula in CD, the population-based SK-IBD study by Park et al. [1] reported that perianal fistula or abscess was present before or at the time of CD diagnosis in 157 of 360 patients (43.6%) diagnosed between 2011 and 2015. Similarly, in a nationwide population-based cohort from the HIRA database, Song et al. [117] reported that the cumulative incidence of perianal fistula or abscess was 35.2% at 1 year, 37.9% at 3 years, and 40.0% at 5 years after CD diagnosis. In the same study, a hospital-based cohort from Asan Medical Center, which included 2,923 patients diagnosed between 1981 and 2015, showed substantially higher cumulative incidence rates: 47.7% at 1 year, 53.3% at 5 years, 57.1% at 10 years, 62.5% at 20 years, and 63.3% at 30 years after CD diagnosis [117]. In contrast, Western studies have reported significantly lower cumulative incidences, with 10-year rates of only 16% and 25% in 2 studies from Europe [118,119] and 21% in 1 study from the United States [120]. These findings suggest that Korean patients with CD have a markedly higher risk of developing perianal fistula or abscess, which may represent a distinctive clinical characteristic compared with Western populations.
Lee et al. [121] were the first to propose that colorectal cancer (CRC) in Korean patients with CD occurs predominantly in the anorectal region. In their 2015 hospital-based cohort study of 2,414 CD patients, 11 (91.7%) of 12 CRC cases developed in the low rectum, which they highlighted as a notable difference compared with Western patients with CD, in whom colon cancer is more common than rectal cancer. Furthermore, they found that patients with a perianal fistula had a significantly higher cumulative probability of developing rectal cancer than those without, suggesting that the high prevalence of perianal fistula in Korean patients with CD may contribute to the predominance of rectal cancer in this population [121]. This hypothesis has since been supported by subsequent studies [122,123]. Suttichaimongkol et al. [122] compared the clinical features of CD-associated CRC in Korea and the United States by analyzing 236 patients treated between 1989 and 2022, including 36 from Asan Medical Center and 200 from the Mayo Clinic. The proportion of rectal cancer among CRC cases was significantly higher in the Korean cohort (86.1%) than in the United States cohort (42.5%). In addition, the prevalence of perianal fistulas was significantly higher in Korean patients, both at the time of CD diagnosis (52.8% vs. 10.1%) and at the time of CRC diagnosis (69.4% vs. 25.0%). A 2023 meta-analysis by Johansen et al. [123] further confirmed that CD patients with a perianal fistula have a higher risk of developing CRC than those without.
4. Treatment
This period was characterized by several notable developments in the treatment of IBD in Korea. First, biologic agents were introduced and progressively integrated into clinical practice. Second, as awareness of IBD improved and clinical experience accumulated, the use of corticosteroids declined, whereas the prescription of thiopurines increased. Third, these advances in medical therapy were accompanied by a gradual reduction in hospitalization and surgery rates.
The introduction of biologic agents significantly advanced the treatment of IBD. In Korea, infliximab, the first biologic agent, was approved for CD in 2000 and became reimbursable in 2003. For UC, infliximab was approved in 2007 and became reimbursable in 2010. These milestones collectively marked the beginning of the biologic era in IBD treatment in Korea. Subsequently, several additional biologic agents, including adalimumab, golimumab, vedolizumab, and ustekinumab, were approved and became reimbursable between 2007 and 2019, further expanding therapeutic options and enabling more personalized treatment strategies. Notably, the world’s first biosimilar to infliximab, CT-P13 (marketed as Remsima in Korea), which had been developed by a Korean company, was approved and became reimbursable in 2012. Its introduction not only improved treatment accessibility but also stimulated growing interest in the cost-effectiveness of biological therapies. In addition, tofacitinib, the first oral small molecule drug for IBD, was approved for UC in 2018 and became reimbursable in 2019, further expanding treatment options beyond injectable biologics. However, the increased use of biologics has also been a key contributor to rising healthcare costs for IBD in Korea. According to a nationwide population-based study using the HIRA database [124], the total annual healthcare costs for IBD increased from $24.5 million in 2008 to $105.1 million in 2017. Of these, the total annual medication costs rose from $13.3 million to $76.8 million, accounting for 54.2% of total annual healthcare costs in 2008 and 73.3% in 2017. Notably, this sharp increase in medication costs was primarily attributable to the rising expenditure on anti-tumor necrosis factor (TNF) agents. The annual cost of anti-TNF agents increased markedly from $1.5 million in 2008 to $49.3 million in 2017, accounting for 64.1% of the total medication costs and 46.9% of the total healthcare costs for IBD in 2017 [124].
During this period, the treatment paradigm for IBD in Korea underwent a substantial transformation, characterized by increasing use of immunomodulators and biologics, alongside a decreasing reliance on corticosteroids. According to a nationwide population-based study using the HIRA database [8], the proportion of patients prescribed immunomodulators at least once in a given year increased from 13.1% to 16.8% in UC and from 52.1% to 61.3% in CD between 2010 and 2018. Similarly, the proportion of patients prescribed biologics rose from 0.7% to 8.2% in UC and from 11.9% to 36.6% in CD over the same period. In contrast, the annual proportion of patients receiving corticosteroids decreased from 23.8% to 18.2% in UC and from 32.1% to 25.2% in CD. Meanwhile, the proportion of patients receiving 5-ASA remained stable in UC at around 93.0%, but declined in CD from 87.9% in 2010 to 72.4% in 2018 [8]. These trends were further supported by longitudinal cohort data from the SK-IBD Research Group [53,55]. In UC, Cha et al. [53] reported that the 1- and 5-year cumulative risks of initiating thiopurines increased from 0.0% and 2.8% in the 1986–1999 cohort to 6.7% and 13.5% in the 2010–2015 cohort. The corresponding risks of initiating anti-TNF agents rose from 0.0% and 1.7% in the 2000–2009 cohort to 3.0% and 8.3% in the 2010–2015 cohort. In contrast, the 1- and 5-year cumulative risks of starting corticosteroids decreased from 33.6% and 50.0% in the 1986–1999 cohort to 22.9% and 31.6% in the 2010–2015 cohort. In CD, Ye et al. [55] found that the 1-, 5-, and 10-year cumulative risks of initiating thiopurines increased from 16.4%, 43.3%, and 67.3% in the 1986–2003 cohort to 57.4%, 78.3%, and 84.6% in the 2004–2015 cohort. Similarly, the corresponding risks of initiating anti-TNF agents rose from 0.0%, 2.8%, and 11.4% in the 1986–2003 cohort to 8.8%, 24.5%, and 38.6% in the 2004–2015 cohort. In contrast, the 1-, 5-, and 10-year cumulative risks of starting corticosteroids decreased from 45.5%, 62.6%, and 70.7% to 41.3%, 49.2%, and 53.9% over the same periods.
As medical therapy evolved, hospitalization and surgery rates among patients with IBD declined. According to the nationwide population-based study by Kim et al. [8], hospitalization rates between 2010 and 2018 decreased from 8.9% to 7.1% in UC and from 24.1% to 20.1% in CD. Meanwhile, the surgery rate for UC declined from 0.4% in 2010 to 0.2% in 2014, after which it remained relatively stable. In contrast, the surgery rate for CD showed a continuous decline from 3.4% in 2010 to 2.3% in 2018. These nationwide trends were consistent with findings from 2 longitudinal SK-IBD cohort studies [53,55]. In UC, Cha et al. [53] reported that the cumulative risk of hospitalization at 1 and 5 years after diagnosis significantly decreased from 16.4% and 25.3% in the 1986–1999 cohort to 9.5% and 12.5% in the 2010–2015 cohort. Similarly, the cumulative risk of colectomy at 1 and 5 years declined from 4.6% and 4.6% to 0.0% and 0.8%, respectively. In CD, Ye et al. [55] found that the cumulative risk of hospitalization at 1, 5, and 10 years after diagnosis decreased from 42.8%, 52.2%, and 68.7% in the 1986–1999 cohort to 27.0%, 36.6%, and 43.7% in the 2010–2015 cohort. Likewise, the cumulative risk of intestinal resection at 1, 5, and 10 years declined from 16.4%, 20.1%, and 32.5% to 11.4%, 15.1%, and 18.7%, respectively.
Building on these observed trends, comparisons with Western data reveal potential differences in disease course and management outcomes [125]. Regarding UC, a global meta-analysis by Tsai et al. [126] reported a 5-year cumulative colectomy rate of 7.0% among patients diagnosed between 2000 and 2016. Similarly, Zhao et al.’s review [119] of European studies published between 2010 and 2020 reported 5-year cumulative colectomy rates ranging from 3% to 8%. In comparison, the corresponding rate in the 2010–2015 SK-IBD UC cohort was substantially lower at 0.8% [53]. For CD, Tsai et al. [126] reported 5- and 10-year cumulative risks of intestinal resection at 18.0% and 26.2%, respectively, in patients diagnosed between 2000 and 2015. Zhao et al. [119] similarly reported 5-year rates ranging from 12% to 27% across European studies. In this context, the 2004–2015 SK-IBD CD cohort showed slightly lower rates of 15.1% at 5 years and 18.7% at 10 years after diagnosis [55]. Hospitalization rates also appear to be lower in Korean cohorts. In UC, Zhao et al. [119] reported 5-year hospitalization rates ranging from 18% to 54% in European studies, whereas the rate was 12.5% in the 2010–2015 SK-IBD UC cohort [53]. In CD, the corresponding rates were 44% to 54% in Europe [119], compared with 36.6% in the 2004–2015 SK-IBD cohort [55].
1. Research Environment and Trends
The 2020–2024 period was marked by continued quantitative growth and structural consolidation in IBD research in Korea. During this 5-year span, a total of 1,084 IBD-related publications from Korea were indexed in PubMed, comprising 803 original articles, 168 review articles (including 26 meta-analyses and 7 clinical guidelines or consensus statements), 47 case reports, and 66 other publications (Table 1). Notably, after peaking in 2022, the number of IBD-related publications, particularly clinical research articles, declined for two consecutive years in 2023 and 2024 (Fig. 2). This trend may reflect year-to-year variation or a delayed consequence of the COVID-19 pandemic. The potential impact of ongoing healthcare policy conflicts in Korea may become more evident in the coming years.
Multicenter collaborative studies and nationwide population-based research using the HIRA database have remained key pillars of IBD research in Korea. Among 376 clinical research papers published between 2000 and 2024, 101 (26.9%) were multicenter studies, including 26 (6.9%) led by the KASID IBD Research Group, and 84 (22.3%) utilized HIRA data, reflecting the sustained growth of Korea’s IBD research ecosystem. Studies using the HIRA database tended to be published more frequently in higher-impact journals (IF ≥5.0) than KASID-led multicenter studies (Supplementary Tables 1 and 2). This likely reflects the inherent strengths of HIRA databased studies, which are both nationwide and population-based in design. In contrast, despite their rich clinical data, KASID-led multicenter studies often face operational and logistical challenges that may limit their publication impact, highlighting the need for strategic efforts to enhance research quality and visibility.
During this period, in addition to AOCC-based international studies [127-131], Korean researchers increasingly engaged in international clinical research and, in some instances, took leading roles in collaborative studies with Western investigators, marking an important step toward deeper global integration beyond Asia [122,132-134]. In parallel, the domestic research landscape began to incorporate emerging global trends such as the clinical application of artificial intelligence (AI) and precision medicine [135,136]. A pioneering example was published in 2020 by Youn I Choi of Gachon University [137], who developed a machine learning model to predict the 5-year risk of biologic use in patients with IBD, marking the introduction of AI-driven research in the field.
Although forecasting scientific trends is inherently uncertain, current trajectories suggest that the next 15 years will be shaped by deeper integration of digital technologies and precision medicine in IBD research. Emerging methodologies, such as AI-driven predictive modeling, natural language processing of medical records, and deep phenotyping through the integration of clinical, genetic, microbiome, and lifestyle data, are expected to drive the evolving research agenda. Infrastructural advances, including national biobanks and digital health records, may further support this transformation by enabling large-scale longitudinal studies with unprecedented granularity. Korean investigators are also expected to play an increasingly central role in global IBD research. Building on prior successes, they may lead multinational randomized controlled trials and contribute to the development of Asia-specific clinical guidelines. Meanwhile, as Korea’s IBD population continues to grow and age, research priorities may increasingly shift toward long-term disease outcomes, cancer surveillance, aging-related complications, and the sustainability of healthcare expenditures. Ultimately, the convergence of clinical research, public health data, and digital innovation holds the potential to usher in a new era of patient-centered, data-driven IBD research.
2. Diagnostic Process
During this period, small bowel follow-through, previously a mainstay for evaluating small bowel involvement in CD, was effectively phased out. With the widespread adoption of CT and MR enterography in the previous decade, the 2020s witnessed a near-complete transition to cross-sectional imaging for small bowel assessment. Notably, although CT enterography was initially more commonly used, MR enterography has since become the preferred modality in many centers, due to its lack of radiation exposure, rendering it more suitable for repeated evaluations.
Although AI has not yet been integrated into routine clinical diagnostics for IBD, research efforts in this area have been steadily increasing globally, with growing research interest in Korea. Several Korean studies have applied deep learning or machine learning techniques to colonoscopy [138-140], MR enterography [141], and capsule endoscopy [142] for the diagnosis, differentiation, or activity scoring of UC and CD. Other studies have explored the use of machine learning models to analyze fecal or oral microbiome profiles [143,144] or RNA sequencing data from endoscopic biopsy tissues [145] for diagnostic applications. These approaches, however, remain largely investigational at this stage.
Building on these advances, diagnostic strategies for IBD are likely to undergo further transformation in the coming years. AI-driven decision support systems may be integrated into endoscopic and cross-sectional imaging platforms, with the potential to offer real-time interpretation of colonoscopic and radiologic findings. In addition, multi-omics approaches, including microbiome profiling, transcriptomics, and metabolomics, are expected to improve diagnostic precision and enable earlier and more accurate differentiation between UC and CD. These data streams may further support predictive models for disease trajectory at the time of diagnosis, thereby guiding individualized treatment decisions. In parallel, wearable devices and novel sensing technologies, such as smart toilets, may enable the longitudinal, real-time capture of physiologic and biomarker data, supplementing conventional diagnostics with continuous, non-invasive monitoring. Collectively, these advances may help address the persistent diagnostic challenges discussed in previous sections, particularly diagnostic delays and difficulties in differentiating CD from intestinal TB, while paving the way for more proactive and personalized care.
3. Patient Population and Characteristics
As of 2025, no studies have reported the incidence or prevalence of IBD in Korea during 2020–2024. However, previous studies examining trends between 2000 and 2019 have suggested that the upward trajectory of IBD incidence began to slow in the 2010s, with the incidence of CD stabilizing between 2014 and 2018 [1,8]. In this context, future population-based data will be crucial to determine whether this deceleration will persist or whether the incidence of IBD may even begin to decline.
According to the 4-stage model of IBD evolution proposed by Kaplan and Windsor [10], most Western countries are currently considered in stage 3 (Compounding Prevalence), while the majority of Asian countries remain in stage 2 (Acceleration in Incidence), with some still classified as being in stage 1 (Emergence). In Korea, data indicating a plateauing trend in incidence since the mid-2010s [1,8] suggest that the country may be approaching the end of stage 2, or even beginning to transition into stage 3 during the 2020–2039 period. However, this remains uncertain given the relatively short observation window. Ongoing and future studies in the 2020s will be essential to clarify whether incidence will continue to rise, stabilize, or decline, thereby clarifying Korea’s position within the global framework of IBD evolution.
In contrast to incidence trends, the prevalence of IBD is projected to continue rising for the foreseeable future. Park et al. [1] estimated that, assuming a stable incidence rate of 9.00 per 100,000 as of 2015, a median age at diagnosis of 31 years, and a life expectancy of 75 years, the prevalence would ultimately reach 396 per 100,000. In contrast, Kim et al. [8], using an autoregressive integrated moving average (ARIMA) model, projected that the prevalence of IBD would reach 240 per 100,000 by 2048. These differing projections underscore the importance of future population-based studies to clarify the long-term trajectory of IBD prevalence in Korea.
Although no nationwide studies have reported patient characteristics focused on the 2020–2024 period, current clinical observations suggest no major deviations from previously established patient profiles. However, population aging is expected to drive important changes in the demographic profile of IBD, increasing the proportion of elderly-onset cases and older patients with longstanding disease. These trends will likely require greater attention to comorbidity management, polypharmacy, and age-specific care strategies.
4. Treatment
During the 2020–2024 period, the therapeutic landscape for IBD in Korea continued to evolve with the introduction of several new agents. These included oral small molecule drugs such as filgotinib, upadacitinib, and ozanimod, as well as subcutaneous formulations of infliximab and vedolizumab. In addition, biosimilars of adalimumab (Adaloce, Yuflyma) and ustekinumab (Epyztek, Steqeyma) became available, improving treatment accessibility and reinforcing the shift toward more cost-effective care. Collectively, these developments broadened therapeutic options and increased the complexity of clinical decision-making, prompting greater interest in treatment sequencing, switching strategies, combination regimens, and personalized approaches.
At the same time, Korean researchers began exploring the potential of AI and machine learning to inform personalized treatment strategies for IBD. Early studies developed AI-based models to predict the 5-year risk of initiating biologic therapy using clinical data [137], and to forecast treatment responses based on gut microbiota profiles [146,147], fecal metabolomic signatures [148], and transcriptomes imputed from genotype data [149]. Another study applied machine learning algorithms to predict the risk of early intestinal resection using integrated clinical and genetic information [150]. Although these tools remain investigational, they represent meaningful progress toward the implementation of precision medicine in IBD care.
Looking ahead, the next 15 years are likely to bring further advances in AI-driven precision medicine, including clinical decision support systems that integrate multi-omics data, imaging, and real-time monitoring from wearable biosensors. In parallel, AI is expected to play an increasingly important role in drug discovery and development by accelerating target identification and optimizing clinical trial design. As therapeutic innovations and AI-based approaches continue to evolve, it will be of considerable interest to observe to what extent hospitalization and surgery rates in IBD will continue to decline over the coming decades.
Since the first reported cases of IBD in Korea in 1961, the country has witnessed a dramatic increase in the incidence and prevalence of both UC and CD. Over the past 6 decades, Korea’s IBD landscape has undergone profound transformation in terms of clinical awareness, diagnostic approaches, therapeutic strategies, and research infrastructure. This review has outlined the evolution of IBD research in Korea, from sporadic case reports to a robust and dynamic ecosystem characterized by multicenter collaboration, population-based cohort studies, and increasing integration into the global research community. Clinically, advances such as the widespread use of colonoscopy and cross-sectional imaging, the introduction of biologics and small molecule drugs, and the growing emphasis on precision medicine have fundamentally reshaped patient care. Notably, Korean patients with IBD exhibit several distinctive epidemiological and clinical features compared with their Western counterparts, including a markedly higher proportion of proctitis and a lower long-term risk of colectomy in UC, as well as a strikingly higher prevalence of perianal fistulas in CD.
As Korea approaches the third epidemiological stage of IBD evolution, research efforts continue to progress, increasingly shaped by digital innovation, AI, and large-scale data integration. While this review has primarily focused on clinical research, future reviews encompassing basic and translational studies will be valuable in providing a more comprehensive picture of IBD research in the Korean context. As the physicist Niels Bohr famously remarked, “Prediction is very difficult, especially if it’s about the future,” a quote that aptly reflects the uncertainty inherent in forecasting the trajectory of scientific research. Yet based on current trends, the outlook for IBD research in Korea appears highly promising. Continued efforts to foster multidisciplinary collaboration, strengthen national data integration, promote innovation-driven research, and expand international research partnerships will be essential in shaping the future course of IBD research in Korea.

Funding Source

The author received no financial support for the research, authorship, and/or publication of this article.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Data Availability Statement

Not applicable.

Author Contributions

Writing and approval of the final manuscript: Yang SK.

Supplementary materials are available at the Intestinal Research website (https://www.irjournal.org).

Supplementary Table 1.

Impact Factors of KASID-Led Multicenter Studies (2005–2024)
ir-2025-00073-Supplementary-Table-1.pdf

Supplementary Table 2.

Impact Factors of Nationwide Population-based Studies Using the HIRA Database (2015–2024)
ir-2025-00073-Supplementary-Table-2.pdf

Supplementary References

ir-2025-00073-Supplementary-References.pdf
Fig. 1.
Age- and sex-adjusted annual incidence of Crohn’s disease and ulcerative colitis in the Songpa-Kangdong district, Seoul, 1986–2015. Adapted from Park SH et al. J Crohns Colitis 2019;13:1410-1417, with permission from Oxford University Press [1].
ir-2025-00073f1.jpg
Fig. 2.
Annual number of PubMed-indexed publications on inflammatory bowel disease from Korea, 1987–2024, including total publications, original research articles, and clinical research articles, with the latter presented as a subset of the original articles.
ir-2025-00073f2.jpg
Table 1.
PubMed-Indexed IBD-Related Publications from Korea by Period and Type
Type of articles Period
Overall 1960–1979 (n = 0) 1980–1999 (n = 23) 2000–2019 (n = 1,355) 2020–2024 (n = 1,084)
Original articles 1,719 0 17 899 803
 Clinical research 792 0 10 406 376
 Basic/translational research 927 0 7 493 427
Non-original articles 743 0 6 456 281
 Review articles 387 0 2 217 168
 Case reports 214 0 4 163 47
 Others 142 0 0 76 66
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        Evolution of inflammatory bowel disease in Korea: a 60-year perspective on clinical and research development
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      Evolution of inflammatory bowel disease in Korea: a 60-year perspective on clinical and research development
      Image Image
      Fig. 1. Age- and sex-adjusted annual incidence of Crohn’s disease and ulcerative colitis in the Songpa-Kangdong district, Seoul, 1986–2015. Adapted from Park SH et al. J Crohns Colitis 2019;13:1410-1417, with permission from Oxford University Press [1].
      Fig. 2. Annual number of PubMed-indexed publications on inflammatory bowel disease from Korea, 1987–2024, including total publications, original research articles, and clinical research articles, with the latter presented as a subset of the original articles.

      Fig. 1.

      Fig. 2.

      Evolution of inflammatory bowel disease in Korea: a 60-year perspective on clinical and research development
      Type of articles Period
      Overall 1960–1979 (n = 0) 1980–1999 (n = 23) 2000–2019 (n = 1,355) 2020–2024 (n = 1,084)
      Original articles 1,719 0 17 899 803
       Clinical research 792 0 10 406 376
       Basic/translational research 927 0 7 493 427
      Non-original articles 743 0 6 456 281
       Review articles 387 0 2 217 168
       Case reports 214 0 4 163 47
       Others 142 0 0 76 66
      Table 1. PubMed-Indexed IBD-Related Publications from Korea by Period and Type

      Table 1.

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