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Background/Aims: Pneumocystis jirovecii pneumonia (PJP) is a rare but potentially fatal infection. This study was conducted to investigate the risk factors for PJP in inflammatory bowel disease (IBD) patients. Methods: This nationwide, population-based study was conducted in Korea using claims data. Cases of PJP were identified in patients diagnosed with ulcerative colitis (UC) or Crohn’s disease (CD) between 2010 and 2017, and the clinical data of each patient was analyzed. Dual and triple therapy was defined as the simultaneous prescription of two or three of the following drugs: steroids, calcineurin inhibitors, immunomodulators, and biologics. Results: During the mean follow-up period (4.6±2.3 years), 84 cases of PJP were identified in 39,462 IBD patients (31 CD and 53 UC). For CD patients, only age at diagnosis >40 years (hazard ratio [HR], 6.12; 95% confidence interval [CI], 1.58 to 23.80) was significantly associated with the risk of PJP, whereas in UC patients, diagnoses of diabetes (HR, 2.51; 95% CI, 1.19 to 5.31) and chronic obstructive pulmonary disease (HR, 3.41; 95% CI, 1.78 to 6.52) showed significant associations with PJP risk. Triple therapy increased PJP risk in both UC (HR, 3.90; 95% CI, 1.54 to 9.88) and CD patients (HR, 5.69; 95% CI, 2.32 to 14.48). However, dual therapy increased PJP risk only in UC patients (HR, 2.53; 95% CI, 1.36 to 4.70). Additionally, 23 patients (27%) received intensive care treatment, and 10 (12%) died within 30 days. Conclusions: PJP risk factors differ in CD and UC patients. Considering the potential fatality of PJP, prophylaxis should be considered for at-risk IBD patients. [ABSTRACT FROM AUTHOR]

Background/Aims: Owing to the low prevalence of small-bowel adenocarcinoma (SBA), data on the impact of Crohn’s disease (CD) on the survival of patients with SBA are lacking. Therefore, we investigated this issue in this study. Methods: In this bicenter cohort study, patients with histologically confirmed SBA were retrospectively enrolled and classified into two groups: sporadic SBA and CD-associated SBA. Patients with duodenal SBA were excluded. Overall survival, disease-free survival, and factors associated with survival were analyzed. Results: Of 128 patients with SBA, 115 had sporadic SBA and 13 had CD-associated SBA. Ileal involvement and poorly differentiated tumors were more common in the CD-associated SBA group than in the sporadic SBA group (ileal involvement, 53.8% vs 22.6%; poor differentiation, 46.2% vs 14.8%; both p<0.05). In survival analysis, overall survival showed no statistical difference between the sporadic SBA and CD-associated SBA groups (p=0.370). However, when stratified by stage, the adjusted overall survival of the CD-associated SBA group was lower in patients with an advanced disease stage (p=0.029). Disease-free survival showed the same tendency, albeit without clinical significance (p=0.097). CD (hazard ratio [HR], 2.308; p=0.047), older age (≥65 yr) at SBA diagnosis (HR, 2.766; p=0.001), and stage III/IV disease (HR, 3.151; p<0.001) were factors associated with mortality. Conclusions: The overall survival of patients with CD-associated SBA did not differ from that of patients with sporadic SBA. However, as CD is an independent risk factor for mortality, vigilant surveillance in high-risk patients may be crucial. [ABSTRACT FROM AUTHOR]

Crohn’s disease (CD) is a relapsing and progressive condition characterized by diarrhea, abdominal pain, weight loss, and hematochezia that results in serious complications such as perforations, fistulas, and abscesses. Various medications, interventions, and surgical treatments have been used to treat CD. The Korean guidelines for CD management were distributed in 2012 and revised in 2017 by the Inflammatory Bowel Disease (IBD) Research Group of the Korean Association for the Study of Intestinal Diseases. Substantial progress in mucosal immunologic research has elucidated the pathophysiology of IBD, leading to development of biological agents for treatment of CD. The first developed biologic agent, tumor necrosis factor-α agents, were shown to be efficacious in CD, heralding a new era in management of CD. Subsequently, vedolizumab, a monoclonal antibody against integrin α4β7, and ustekinumab, a human monoclonal antibody that inhibits the common p40 subunit of interleukin-12 and interleukin-23, were both approved for clinical use and are efficacious and safe for both induction and maintenance of remission in moderate-to-severe CD patients. Moreover, a recent study showed the non-inferiority of CT-P13, an infliximab biosimilar, compared with infliximab in CD patients. The third Korean guidelines for CD management provide updated information regarding treatment of moderate-to-severe CD patients with biologic agents. [ABSTRACT FROM AUTHOR]

The clinical course and prognosis of patients with elderly-onset Crohn’s disease (CD) remain unclear. This study aimed to analyze the clinical characteristics and outcomes of elderly-onset CD patients from the prospective CONNECT study cohort, a nationwide, multicenter cohort study of patients with CD in Korea. Among a total of 1,175 patients in the prospective CONNECT study cohort, 94 patients (Montreal age A3) were included and divided into two groups according to their age at diagnosis: the elderly-onset group (diagnosed with CD after 60 years of age, n=26, 67.54±6.7 years) and late adult-onset group (diagnosed as CD at age 41 to 59 years, n=68, 48.06±5.1 years). The elderly-onset group was characterized by a lower Crohn’s disease activity index at diagnosis (124.89±101.9 vs 189.55±128.6, p=0.023) and higher rates of previous anti-tuberculosis treatment (34.6% vs 4.4%, p<0.001) than the late adult-onset group. Compared with the late adult-onset group, the elderly-onset group showed a significantly less use of thiopurines (p=0.003), as well as anti-tumor necrosis factor-alpha agents (p=0.047). Additionally, the elderly-onset group was less likely to require bowel resection than the late adult-onset group (p=0.067), suggesting that elderly-onset CD patients in Korea appear to have more favorable clinical outcomes than late adult-onset CD patients. [ABSTRACT FROM AUTHOR]

Background/Aims: The long-term course of Crohn’s disease (CD) has never been evaluated in non-Caucasian population-based cohorts. The aim of the present study was to evaluate the longterm prognosis of Korean CD patients in the well-defined population-based Songpa-Kangdong inflammatory bowel disease cohort. Methods: Outcomes of disease and their predictors were evaluated for 418 patients diagnosed with CD between 1986 and 2015. Results: During a median of 123 months, systemic corticosteroids, thiopurines, and anti-tumor necrosis factor (TNF) agents were administered to 58.6%, 81.3%, and 37.1% of patients, respectively. Over time, the cumulative probability of starting corticosteroids significantly decreased (p=0.001), whereas that of starting thiopurines and anti-TNFs significantly increased (both p<0.001). The cumulative probability of behavioral progression was 54.5% at 20 years, and it significantly decreased during the anti-TNF era. Intestinal resection was required for 113 patients (27.0%). The cumulative probabilities of intestinal resection at 1, 5, 10, 20, and 25 years after CD diagnosis were 12.7%, 16.5%, 23.8%, 45.1%, and 51.2%, respectively. Multivariable Cox regression analysis identified stricturing behavior at diagnosis (adjusted hazard ratio [aHR], 2.70; 95% confidence interval [CI], 1.55 to 4.71), penetrating behavior at diagnosis (aHR, 11.15; 95% CI, 6.91 to 17.97), and diagnosis of CD during the anti-TNF era (aHR, 0.51; 95% CI, 0.35 to 0.76) as independently associated with intestinal resection. The standardized mortality ratio among CD patients was 1.36 (95% CI, 0.59 to 2.68). Conclusions: The long-term prognosis of Korean patients with CD is at least as good as that of Western CD patients, as indicated by the low intestinal resection rate. Moreover, behavioral progression and intestinal resection rates have decreased over the past 3 decades. [ABSTRACT FROM AUTHOR]

Crohn's disease is associated with altered body composition, such as low muscle mass, which can affect clinical outcomes. However, there are few studies regarding the effect of sarcopenia on prognosis of Crohn's disease. In this study, we evaluated the body composition at the initial diagnosis of Crohn's disease and analyzed the clinical meaning of sarcopenia. Methods: We conducted a retrospective review of medical records of patients who were diagnosed as Crohn's disease and underwent computed tomography within 3 months after diagnosis. Sarcopenia was defined as an L3 skeletal muscle index (SMI) of < 49 cm2/m2 for men and < 31 cm2/m2 for women. Outcomes such as need for hospitalization, surgery, use of steroids, immunomodulators and biologics were analyzed. Results: A total of 79 patients (male, 73.4%; mean age, 29.9 years) were included and 40 patients (51%) were diagnosed as sarcopenia. C-reactive protein (CRP) level was correlated with sarcopenia (P= 0.044). Erythrocyte sedimentation rate (ESR) showed a tendency to decrease inversely with SMI (r = -0.320, P= 0.008) and hemoglobin and albumin tended to increase in proportion to SMI (hemoglobin: r = 0.271, P= 0.016 and albumin: r = 0.350, P= 0.002). However, there was no statistically significance in time-to-first-event analysis in aspects of sarcopenia. Conclusions: Approximately 50% of patients with newly diagnosed as Crohn's disease had sarcopenia. CRP levels were higher in the sarcopenia group and SMI correlated with ESR, hemoglobin, and albumin. However, none of prognostic values were demonstrated. [ABSTRACT FROM AUTHOR]

Background/Aims: We aimed to investigate the differences in direct healthcare costs between patients with and without inflammatory bowel disease (IBD) and changes in direct healthcare costs before and after IBD diagnosis. Methods: This population-based study identified 34,167 patients with IBD (11,014 patients with Crohn's disease and 23,153 patients with ulcerative colitis) and 102,501 age-and sexmatched subjects without IBD (the control group) from the National Health Insurance database using the International Classification of Disease, 10th revision codes and the rare intractable disease registration program codes. The mean healthcare costs per patient were analyzed for 3 years before and after IBD diagnosis, with follow-up data available until 2015. Results: Total direct healthcare costs increased and peaked at $2,396 during the first year after IBD diagnosis, but subsequently dropped sharply to $1,478 during the second year after diagnosis. Total healthcare costs were higher for the IBD patients than for the control group, even in the third year before the diagnosis ($497 vs $402, p<0.001). The costs for biologics for the treatment of IBD increased steeply over time, rising from $720.8 in the first year after diagnosis to $1,249.6 in the third year after diagnosis (p<0.001). Conclusions: IBD patients incurred the highest direct healthcare costs during the first year after diagnosis. IBD patients had higher costs than the control group even before diagnosis. The cost of biologics increased steeply over time, and it can be assumed that biologics could be the main driver of costs during the early period after IBD diagnosis. [ABSTRACT FROM AUTHOR]

Background/Aims: The risk of herpes zoster (HZ) among patients with inflammatory bowel disease (IBD) remains un-clear in terms of age and metabolic comorbidities, including diabetes mellitus, hypertension, or dyslipidemia. We con-ducted a nationwide population based study to investigate the risk of HZ in patients with IBD. Methods: From 2010 to 2013, a retrospective study was performed using claims data in Korea. We compared the incidence of HZ between 30,100 IBD patients (10,517 Crohn's disease [CD] and 19,583 ul-cerative colitis [UC] patients) and 150,500 non-IBD controls matched by age and sex. Results: During a mean follow-up of 5.0 years, incidence rates of HZ (per 1,000 person-years) were 13.60, 14.99, and 9.19 in the CD, UC, and control groups, respectively. The risk of HZ was significantly higher in patients with CD (adjusted hazard ratio [HR], 2.13; p<0.001) and UC (adjusted HR, 1.40; p<0.001) than in the controls. The impact of CD on developing HZ was significantly more prominent in younger patients (adjusted HR, 2.61 for age <15, whereas 1.39 for age ≥60; interaction p=0.001) and in patients without metabolic comorbidities (adjusted HR, 2.24, whereas 1.59 in those with metabolic comorbidities; interac-tion p=0.015). Moreover, the impact of UC on developing HZ significantly increased in younger patients (adjusted HR, 2.51 in age <15, whereas 1.22 in age ≥60; interaction p=0.014) and patients without metabolic comorbidities (adjusted HR, 1.49 whereas 1.16 in those with metabolic comorbidities; interaction p<0.001). Conclusions: IBD was associated with an increased risk of HZ, especially in younger patients without metabolic comorbidities. [ABSTRACT FROM AUTHOR]

Background/Aims: The exact relationship between vitamin D deficiency and inflammatory bowel disease (IBD) remains unclear. We evaluated the effect of vitamin D3 administration on inflammatory responses and disease severity in patients with IBD. Methods: We investigated the serum 25-hydroxyvitamin D3 [25-(OH)D], C-reactive protein (CRP) levels and the partial Mayo score (PMS) in patients with IBD. Vitamin D3 was administered in patients with either vitamin D deficiency or insuffi- ciency and CRP, serum vitamin D levels and PMS were re-examined at 6 months of administration. Results: In 88 patients with Crohn's disease (CD), a negative correlation was found between serum vitamin D and CRP. In 178 patients with ulcerative colitis (UC), serum vitamin D showed no association with CRP or PMS. Serum vitamin D increased from 11.08 ± 3.63 to 22.69 ± 6.11 ng/mL in 29 patients with CD and from 11.45 ± 4.10 to 24.20 ± 6.61 ng/mL in 41 patients with UC who received vitamin D3 treatment (P< 0.001 and P< 0.001, respectively). In patients with CD, median ΔCRP was -0.24 in the normalized vitamin D group and -0.11 in the non-normalized group (P= 0.308). In patients with UC, median ΔCRP was -0.01 in the normalized vitamin D group and 0.06 in the non-normalized group (P= 0.359). Conclusions: Although a negative correlation was found between serum vitamin D and CRP levels in patients with CD, administration of vitamin D did not improve the CRP level in patients with CD. In patients with UC, serum vitamin D level was unrelated to CRP or PMS. [ABSTRACT FROM AUTHOR]

Background/Aims: The disease course and factors associated with poor prognosis in Korean patients with Crohn's disease (CD) have not been fully determined. The aim of this study was to explore potential associations between the clinical characteristics and long-term outcomes of CD and perianal fistulas in a Korean population. Methods: The retrospective Crohn's Disease Clinical Network and Cohort (CONNECT) study enrolled patients diagnosed with CD between July 1982 and December 2008 from 32 hospitals. Those followed for <12 months were excluded. Clinical outcomes were CD-related surgery and complications, including nonperianal fistulas, strictures, and intra-abdominal abscesses. Results: The mean follow-up period was 8.77 years (range, 1.0 to 25.8 years). A total of 1,193 CD patients were enrolled, of whom 465 (39.0%) experienced perianal fistulas. Perianal fistulizing CD was significantly associated with younger age, male gender, CD diagnosed at primary care clinics, and ileocolonic involvement. Both nonperianal fistulas (p=0.034) and intra-abdominal abscesses (p=0.020) were significantly more common in CD patients with perianal fistulas than in those without perianal fistulas. The rates of complicated strictures and CD-related surgery were similar between the groups. Independently associated factors of nonperianal fistulas were perianal fistulas (p=0.015), female gender (p=0.048), CD diagnosed at referral hospital (p=0.003), and upper gastrointestinal (UGI) involvement (p=0.001). Furthermore, perianal fistulas (p=0.048) and UGI involvement (p=0.012) were independently associated with the risk of intra-abdominal abscesses. Conclusions: Perianal fistulas predicted the development of nonperianal fistulas and intra-abdominal abscesses in Korean CD patients. Therefore, patients with perianal fistulizing CD should be carefully monitored for complicated fistulas or abscesses. [ABSTRACT FROM AUTHOR]

Background/Aims: We aimed to evaluate the clinical characteristics and prognosis of Crohn's disease (CD) in patients who showed proximal small bowel involvement using a nationwide Korean CD cohort. Methods: We reviewed the data from a cohort of patients diagnosed with CD. The clinical outcomes of patients were evaluated according to the presence of proximal small bowel involvement. Results: Among 1,329 patients with CD for whom complete disease location data were available, 222 patients (16.7%) showed involvement of the proximal small bowel. Compared to patients without proximal small bowel involvement, those with small bowel involvement were more likely to display stricturing behavior (19.8% vs 12.7%, p=0.020). The surgery-free survival of patients who showed proximal small bowel involvement was inferior to that of patients without proximal small bowel involvement (10-year surgery-free survival: 58.4% vs 67.7%, respectively, p<0.001). Additionally, upper gastrointestinal involvement was more common in patients with proximal small bowel involvement than in those without involvement (odds ratio, 1.643; 95% confidence interval, 1.008 to 2.677). Conclusions: Proximal small bowel involvement is a poor prognostic factor for the surgery-free survival of Korean patients with CD. Proximal small bowel involvement should be evaluated in patients with CD for predicting long-term clinical outcomes. (Gut Liver 2018;12:67-72) [ABSTRACT FROM AUTHOR]

Background/Aims: The optimal route for iron administration in anemic patients with inflammatory bowel disease (IBD) has not been determined. The aim of this study was to compare the efficacies of parenteral and oral iron therapy in IBD patients in Korea. Methods: A retrospective multicenter study was performed. Patients who had been administered parenteral iron were matched to the controls with oral iron at a 1:1 ratio according to age, sex, and type of IBD. Results: Patients that received parenteral iron exhibited increases in hemoglobin levels of ≥20% from the baseline at lower doses and in shorter durations (p=0.034 and p=0.046, respectively). In the multivariate analysis, parenteral iron therapy appeared to be more efficient than oral iron therapy, but this difference was not statistically significant (hazard ratio [HR], 1.552; 95% confidence interval [CI], 0.844 to 2.851; p=0.157). Patients with ulcerative colitis responded better to iron therapy than those with Crohn's disease (HR, 3.415; 95% CI, 1.808 to 6.450; p<0.001). Patients with an initial hemoglobin level of 10 g/dL or higher responded poorly to iron therapy (HR, 0.345; 95% CI, 0.177 to 0.671; p=0.002). Conclusions: Parenteral iron therapy appears to be more efficient than oral iron therapy. Physicians should focus on the iron deficiency of IBD patients and consider parenteral iron supplements in appropriate patient groups. [ABSTRACT FROM AUTHOR]

Background/Aims: Gastric pathology and Helicobacter pylori (H. pylori) infection among Asian patients with Crohn's disease (CD) are still unclear. We evaluated gastric histologic features and frequency of H. pylori infection in Korean patients with CD. Methods: Among 492 patients with CD receiving upper gastrointestinal (GI) endoscopic evaluation in 19 Korean hospitals, we evaluated the endoscopic findings and gastric histopathologic features of 47 patients for our study. Histopathologic classification was performed using gastric biopsy tissues, and H. pylori infection was determined using the rapid urease test and histology. Results: There were 36 men (76.6%), and the median age of patients at the time of upper GI endoscopy was 23.8 years (range, 14.2-60.5). For CD phenotype, ileocolonic disease was observed in 38 patients (80.9%), and non-stricturing, nonpenetrating disease in 31 patients (66.0%). Twenty-eight patients (59.6%) complained of upper GI symptoms. Erosive gastritis was the most common gross gastric feature (66.0%). Histopathologically, H. pylori -negative chronic active gastritis (38.3%) was the most frequent finding. H. pylori testing was positive in 11 patients (23.4%), and gastric noncaseating granulomata were detected in 4 patients (8.5%). Gastric noncaseating granuloma showed a statistically significant association with perianal abscess/ fistula (P =0.0496). Conclusions: H. pylori -negative chronic active gastritis appears to be frequent among Korean patients with CD. The frequency of H. pylori infection was comparable with previous studies. An association with perianal complications suggests a prognostic value for gastric noncaseating granuloma in patients with CD. [ABSTRACT FROM AUTHOR]

Background: Free perforation is the most severe and debilitating complication associated with Crohn's disease (CD), and it usually requires emergency surgery. The aim of this study was to evaluate the incidence of free perforation among Korean patients with CD. Methods: The CrOhn's disease cliNical NEtwork and CohorT (CONNECT) study was conducted nationwide in Korea, and patients who were diagnosed with CD between 1982 and 2008 were included in this retrospective study. We investigated the incidence of free perforation among these patients and their clinical characteristics. Results: A total of 1346 patients were analyzed and 88 patients (6.5%) were identified with free perforation in CD. The mean age of the free perforation group was 31.8 ± 13.0 years, which was significantly higher than that of the non-perforated group (27.5 ± 12.1 years) (p = 0.004). Free perforation was the presenting sign of CD in 46 patients (52%). Of the 94 perforations that were present in 88 patients, 81 involved the ileum. Multivariate logistic regression analysis determined that free perforation was significantly associated with being aged ⩾ 30 years at diagnosis (OR 2.082, p = 0.002) and bowel strictures (OR 1.982, p = 0.004). The mortality rate in the free perforation group was significantly higher (4.5%) than that in the non-perforated group (0.6%) (p < 0.001). Conclusion: The incidence of free perforation in Korean patients with CD was 6.5%. Being aged ⩾ 30 years at CD diagnosis and bowel strictures were significant risk factors associated with free perforation. [ABSTRACT FROM AUTHOR]

The authors discuss the Crohn's Disease Clinical Network and Cohort (CONNECT) Study, which is considered as the first toward a nationwide multicenter research of Crohn's disease (CD) in Korea. They mention a study by Won Ho Kim at Yonsei University, president of the Korean Association for the Study of Intestinal Diseases (KASID) and obtained the Research Network for Chron's Disease grant. They say that the CONNECT study should help clinicians and researchers on accurately defining CD prognosis.

Background/Aims The association between atopic diseases and inflammatory bowel diseases (IBD) remains unclear. We conducted a nationwide population-based study to investigate the effect of atopic diseases on the development of IBD. Methods A total of 9,950,548 subjects who received medical check-up in 2009 were included and followed up until 2017. The presence of atopic diseases including atopic dermatitis (AD), allergic rhinitis (AR), and asthma were evaluated. Patients who developed IBD including Crohn's disease (CD) and ulcerative colitis (UC) were identified using the claims data from National Health Insurance. Results During a mean follow up of 7.3 years, 1,426 subjects (0.014%) developed CD and 5,916 subjects (0.059%) developed UC. The incidences of CD (per 100,000 person-years) were 4.088, 2.255, and 2.344, and the incidences of UC were 11.926, 9.857, and 9.377 in patients with AD, AR, and asthma, respectively. Multivariable analysis revealed that the adjusted hazard ratios (aHR) for incident CD in patients with AD, AR, and asthma were 2.21, 1.33, and 1.59 (95% confidence interval [CI]: 1.251 to 3.896, 1.152 to 1.532, and 1.186 to 2.123, respectively), while the risk for incident UC in patients in AD, AR, and asthma were 1.51, 1.32, and 1.28 (95% CI: 1.081 to 2.101, 1.235 to 1.416, and 1.110 to 1.484, respectively) compared to controls. Moreover, increase in the number of atopic diseases gradually increased the risk for CD and UC; CD showed aHR of 1.36 and 1.65 (95% CI: 1.180 to 1.571 and 1.143 to 2.370), and UC showed aHR of 1.30 and 1.49 (95% CI: 1.216 to 1.398 and 1.247 to 1.170) in one, and two or more atopic diseases, respectively. Conclusions Patients with atopic diseases showed increased association with IBD. [ABSTRACT FROM AUTHOR]

Background/Aims The incidence of inflammatory bowel disease (IBD) is increasing in Asian countries and numerous risk factors associated with the development of IBD have been studied. This study aims to demonstrate risk factors of Crohn's disease (CD) in South Korea and to specify any differences between age groups using the National Health Insurance Service (NHIS) database. Methods A total of 14,060,821 people over 40 years old who received a national health screening program in 2009 were followed up until December 2017. Patients with newly diagnosed CD were enrolled. CD was identified according to the International Classification of Diseases, 10th revision and the rare, intractable disease registration program codes from the NHIS dataset in South Korea. Results During the mean follow-up period of 7.39 years, a total of 1,337 (1.33 per 100,000) patients developed CD. In the middle age group (40 to 64 years old), patients with history of smoking (adjusted hazard ratio [aHR], 1.29; 95% confidence interval [CI], 1.06 to 1.58) and anemia (aHR, 1.99; 95% CI, 1.67 to 2.36) appeared to have significantly higher risk of developing CD. In the old age group (65 years old or older), ex-smoking and anemia also increased risk of CD (aHR, 1.58 [95% CI, 1.16 to 2.18]; aHR, 1.91 [95% CI, 1.53 to 2.38]; respectively). Especially in the middle age group, those with chronic kidney disease had statistically elevated risk of CD (aHR, 1.38; 95% CI, 1.06 to 1.79). Conclusions Ex-smokers and patients with anemia who are over 40 years old are at high risk of developing CD. In the middle age group in particular, chronic kidney disease patients were at higher risk of developing CD. People with potential risk factors need more cautious approach in monitoring CD. [ABSTRACT FROM AUTHOR]

Background/Aims The impact of proteinuria and its severity on the incidence of inflammatory bowel disease (IBD) has not been studied yet. We aimed to determine the association between proteinuria measured by urine dipstick test on the development of IBD. Methods This is a retrospective nationwide population-based study using the National Health Insurance Service (NHIS) database in South Korea. A total of 9,917,400 people aged 20 years or older who had undergone a national health examination conducted by NHIS in 2009 were followed up to 2017. The study population was classified into four groups according to the degree of proteinuria: negative, trace, 1+, and ≥2+. The primary endpoint was the newly diagnosed IBD, Crohn's disease (CD) or ulcerative colitis (UC) during follow- up period. Results Compared with the dipstick negative group, the risk of CD was significantly increased as the degree of proteinuria increased (adjusted hazard ratio [aHR] with 95% confidence interval [CI], 1.01 [0.703 to 1.451], 1.515 [1.058 to 2.162], and 2.053 [1.301 to 3.24] in dipstick trace, 1+, and ≥2+ group, respectively), but there was no significant difference in the risk of UC (aHR with 95% CI, 1.12 [0.949 to 1.323], 0.947 [0.764 to 1.174], 1.009 [0.741 to 1.373]). Dipstick positive proteinuria increased the risk of CD regardless of subgroups. However, in the development of UC, dipstick positive proteinuria increased the risk of UC in those with diabetes mellitus (DM), but not in those without DM (aHR, 1.527 vs 0.846; interaction p-value 0.004). The risk of CD was increased or decreased according to changes in proteinuria but not associated with the risk of UC. Conclusions Proteinuria, measured by dipstick test, is strongly associated with the development of CD. [ABSTRACT FROM AUTHOR]