Corticosteroids and Mesalamine Versus Corticosteroids for Acute Severe Ulcerative Colitis: A Randomized Controlled Trial.

BACKGROUND & AIMS: Corticosteroids are the mainstay of treatment for hospitalized patients with acute severe ulcerative colitis (ASUC). However, whether the addition/continuation of mesalamine with corticosteroids during hospitalization is superior to corticosteroids alone is unknown. METHODS: This was a randomized controlled, investigator-blinded, clinical trial conducted in 10 centers in 7 countries. Patients hospitalized with ASUC (Lichtiger score ≥10) were eligible. Patients received corticosteroids alone or corticosteroid + mesalamine (4 g/day mesalamine) by a stratified randomization according to mesalamine use before admission. The primary outcome was the percentage of patients who responded to treatment by day 7, defined by a drop >3 points in the Lichtiger score and an absolute score <10 without the need for rescue medications or colectomy. RESULTS: Three hundred forty-six patients were screened, and 149 were included (70/149 female; median age, 41 years). Of these, 73 received corticosteroids + mesalamine, and 76 received corticosteroids alone. For the primary outcome, 53 of 73 patients (72.6%) receiving corticosteroids with mesalamine responded versus 58 of 76 patients (76.3%) on corticosteroids alone (odds ratio, 0.82; 95% confidence interval, 0.39-1.72; P = .60). There was no difference between groups in duration of hospitalization, C-reactive protein normalization rate, or colectomy rate up to day 90. The need for biologics among patients receiving combination of corticosteroids with mesalamine was numerically lower by day 30 (P = .11) and day 90 (P = .07). CONCLUSIONS: In this randomized controlled trial, combination of mesalamine with corticosteroids did not benefit hospitalized patients with ASUC more than corticosteroids alone. An exploratory signal for a reduced need for biologics at 90 days in the mesalamine group merits further evaluation. CLINICALTRIALS: gov ID: NCT01941589.

A clinical decision support tool may help to optimise vedolizumab therapy in Crohn's disease.

BACKGROUND: A clinical decision support tool (CDST) has been validated for predicting treatment effectiveness of vedolizumab (VDZ) in Crohn's disease. AIM: To assess the utility of this CDST for predicting exposure-efficacy and disease outcomes. METHODS: Using data from three independent datasets (GEMINI, GETAID and VICTORY), we assessed clinical remission rates and measured VDZ exposure, rapidity of onset of action, response to dose optimisation and progression to surgery by CDST-defined response groups (low, intermediate and high). RESULTS: A linear relationship existed between CDST-defined groups, measured VDZ exposure, rapidity of onset of action and efficacy in GEMINI through week 52 (P < 0.001 at all time points across three CDST-defined groups). In GETAID, CDST predicted differences in clinical remission at week 14 (AUC = 0.68) and rapidity of onset of action (P = 0.04) between probability groups. The high-probability patients did not benefit from shortening of infusion intervals, and differences in onset of action between the high-intermediate and low-probability groups within GETAID were no longer significant when including low-probability patients who received a week 10 infusion. CDST predicted a twofold increase in surgery risk over 12 months of VDZ therapy among low- to intermediate-probability vs high-probability patients (adjusted HR 2.06, 95% CI 1.33-3.21). CONCLUSIONS: We further extended the clinical utility of a previously validated VDZ CDST, which accurately predicts at baseline exposure-efficacy relationships and rapidity of onset of action and could be used to help identify patients who would most benefit from interval shortening and those most likely to require surgery while on active therapy.

Burden and outcomes for complex perianal fistulas in Crohn's disease: Systematic review.

AIM: To systematically review the literature on epidemiology, disease burden, and treatment outcomes for Crohn's disease (CD) patients with complex perianal fistulas. METHODS: PubMed, Embase, and Cochrane were searched for relevant articles (published 2000-November 2016) and congress abstracts (published 2011-November 2016). RESULTS: Of 535 records reviewed, 62 relevant sources were identified (mostly small observational studies). The cumulative incidence of complex perianal fistulas in CD from two referral-centre studies was 12%-14% (follow-up time, 12 years in one study; not reported in the second study). Complex perianal fistulas result in greatly diminished quality of life; up to 59% of patients are at risk of faecal incontinence. Treatments include combinations of medical and surgical interventions and expanded allogeneic adipose-derived stem cells. High proportions of patients experience lack of or inadequate response to treatment (failure and relapse rates, respectively: medical, 12%-73% and 0%-41%; surgical: 0%-100% and 11%-20%; combined medical/surgical: 0%-80% and 0%-50%; stem cells: 29%-47% and not reported). Few studies (1 of infliximab; 3 of surgical interventions) have been conducted in treatment-refractory patients, a population with high unmet needs. Limited data exist on the clinical value of anti-tumour necrosis factor-α dose escalation in patients with complex perianal fistulas in CD. CONCLUSION: Complex perianal fistulas in CD pose substantial clinical and humanistic burden. There is a need for effective treatments, especially for patients refractory to anti-tumour necrosis factor-α agents, as evidenced by high failure and relapse rates.

MDR1 gene polymorphisms are associated with ulcerative colitis in a cohort of Serbian patients with inflammatory bowel disease.

BACKGROUND: Inflammatory bowel disease (IBD) is a chronic disease of unknown etiology in which genetic factors contribute to development of disease. Single nucleotide polymorphisms (SNPs) in multidrug resistance 1 (MDR1) gene encoding transporter P-glycoprotein have been associated with IBD, but their role in disease susceptibility remains unclear. Therefore, the aim of this study was to investigate the association of three MDR1 polymorphisms, C1236T (rs1128503), G2677T/A (rs2032582) and C3435T (rs1045642), with Serbian IBD patients. METHODS: A total of 206 IBD patients, 107 Crohn's disease (CD) and 99 ulcerative colitis (UC), and 255 healthy controls were included in the study. All subjects were genotyped using TaqMan SNP genotyping assays. Comparisons between the groups were performed using the Pearson Chi-square test. False discovery rate according to Benjamini-Hochberg procedure was applied to adjust for multiple comparisons. RESULTS: Carriers of T allele of all three MDR1 SNPs were more common in UC patients compared to healthy controls, suggesting predisposing role of T allele of these SNPs in UC pathogenesis. Consistently, TT genotype of C1236T and TTT haplotype were also found more frequently in UC patients. On the other hand, C allele and CC genotype of C1236T and C3435T, as well as G allele and GG genotype of G2677T/A were more frequent in healthy subjects, implying protective role of these variants in UC. Likewise, CGC haplotype and CGC/CGC diplotype were more frequent in controls. Contrary to UC, no statistical difference was observed between CD patients and controls in any of the SNPs analyzed. CONCLUSION: MDR1 gene variants and haplotypes were associated with UC in Serbian IBD patients, further supporting their potential role in susceptibility to UC.

Patient Reported Outcome Measures (PROMs) in Inflammatory Bowel Disease: New Data.

Patient reported outcome measures [PROMs] are standardized, validated questionnaires intended for completion by patients in order to measure their perceptions of their own health condition or its treatment without interpretation of the patient's response by a clinician or anyone else. Mayo Clinic Score [MCS] or Crohn's Disease Activity Index [CDAI], most frequently used as end points in conventional clinical trials, are composite instruments that are not fully objective nor capture the impact of disease from the patient's perspective. They are difficult to apply to routine clinical practice because they are complex and time consuming. The European Medicines Agency and Food and Drug Administration are re-evaluating composite indices in clinical trials and product development guidelines. The ultimate goal is to support labelling claims to improve safety and effectiveness of medical products through PROMs allied to an objective measure of inflammation, as happens informally in clinical practice. PROMs, developed and validated according to rigorous criteria, are set to become a co-primary end point for clinical trials of therapy, together with objective measure[s] of inflammation. This will affect future trials' design and their results. To find a place in routine care, PROMs should be easy to use, acceptable to patients and healthcare teams, and able to demonstrate added value to normal practice, supporting decision-making at the level of individual patients. Ideally, the same PROMs should be used in clinical trials and practice, to avoid the current disconnect when interpreting the results of clinical trials and translating them into routine clinical practice.

The Polymorphism rs3024505 (C/T) Downstream of the IL10 Gene Is Associated with Crohn's Disease in Serbian Patients with Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD), manifesting as Crohn's disease (CD) and ulcerative colitis (UC), is characterized by recurring episodes of inflammation in gastrointestinal tract, in which aberrant production of regulatory cytokine interleukin-10 (IL-10) presumably plays important role. Single nucleotide polymorphisms (SNPs) that affect IL-10 production, such as rs1800896 (G/A) at position -1082 and rs1800871 (C/T) at position -819 in the promoter region of the IL10 gene, have been associated with CD and/or UC, but the results were inconsistent. Another SNP that may alter IL-10 production, rs3024505 (C/T) located immediately downstream of the IL10 gene has been recently identified. T allele of rs3024505 was associated with both UC and CD in Western populations, but the studies from East European countries are lacking. Therefore, our aim was to assess the association of rs3024505, rs1800896 and rs1800871 with Serbian IBD patients. To this end, 107 CD and 99 UC patients and 255 healthy controls were genotyped. As a result, T allele of rs3024505 was associated with CD at allelic, genotypic (GT genotype) and haplotypic (GCCT haplotype) level, suggesting potential role of this variant in susceptibility to CD. In contrast, CD patients carrying C allele of rs3024505 had significantly increased risk of anemia and stricturing/penetrating behavior. No association was observed between rs3024505 and UC or SNPs in IL10 promoter region and any form of IBD. In conclusion, rs3024505 SNP flanking the IL10 gene is associated with susceptibility and severity of disease in Serbian CD patients, further validating its role as a potential biomarker in IBD.

Inflammatory bowel disease: exploring gut pathophysiology for novel therapeutic targets.

Ulcerative colitis and Crohn's disease are the 2 major phenotypes of inflammatory bowel disease (IBD), which are influenced by a complex interplay of immunological and genetic elements, though the precise etiology still remains unknown. With IBD developing into a globally prevailing disease, there is a need to explore new targets and a thorough understanding of the pathophysiological differences between the healthy and diseased gut could unearth new therapeutic opportunities. In this review, we provide an overview of the major aspects of IBD pathogenesis and thereafter present a comprehensive analysis of the gut pathophysiology leading to a discussion on some of the most promising targets and biologic therapies currently being explored. These include various gut proteins (CXCL-10, GATA-3, NKG2D, CD98, microRNAs), immune cells recruited to the gut (mast cells, eosinophils, toll-like receptors 2, 4), dysregulated proinflammatory cytokines (interleukin-6, -13, -18, -21), and commensal microbiota (probiotics and fecal microbiota transplantation). We also evaluate some of the emerging nonconventional therapies being explored in IBD treatment focusing on the latest developments in stem cell research, oral targeting of the gut-associated lymphoid tissue, novel anti-inflammatory signaling pathway targeting, adenosine deaminase inhibition, and the beneficial effects of antioxidant and nutraceutical therapies. In addition, we highlight the growth of biologics and their targets in IBD by providing information on the preclinical and clinical development of over 60 biopharmaceuticals representing the state of the art in ulcerative colitis and Crohn's disease drug development.

European experience with methotrexate treatment in Crohn's disease: a multicenter retrospective analysis.

INTRODUCTION: Methotrexate (MTX) has been utilized for the treatment of Crohn's disease (CD) for decades. Nevertheless, current data provide equivocal evidence on the efficacy of MTX in CD.The aims of this study were to describe the efficacy of MTX for maintenance of remission in CD and to identify the factors associated with the probability of steroid-free clinical remission in a multicenter European referral center cohort. PATIENTS AND METHODS: This was a retrospective cohort analysis. Consecutive patients treated with MTX for CD were included from 11 referral centers. Patients receiving concomitant treatment with tumor necrosis factor inhibitors or thiopurines were excluded. The main outcome was steroid-free clinical remission; the secondary outcomes included the rate of complications leading to MTX discontinuation and duration of relapse-free survival in patients achieving the main outcome. RESULTS: Between July 1992 and January 2012, 118 patients were identified for inclusion. MTX administration route was oral for induction in 31.4% and for maintenance in 49.1% of the patients. Steroid-free remission was achieved in 44/118 (37.2%) patients and was maintained relapse free by 28/44 (63.6%) for a median of 12 (3.5-18.5) months. At least one adverse effect was reported by 28.9% of the patients. No clinical or demographic factors were associated with either likelihood of achieving a clinical response or duration of relapse-free survival. CONCLUSION: MTX treatment induced steroid-free clinical remission in over a third of CD patients and maintained it for a year in almost two-thirds of the responders. MTX should be considered a viable therapeutic option in CD patients refractory to other therapies.

The effectiveness and safety of rescue treatments in 108 patients with steroid-refractory ulcerative colitis with sequential rescue therapies in a subgroup of patients.

BACKGROUND: Among patients with steroid-refractory ulcerative colitis (UC) in whom a first rescue therapy has failed, a second line salvage treatment can be considered to avoid colectomy. AIM: To evaluate the efficacy and safety of second or third line rescue therapy over a one-year period. METHODS: Response to single or sequential rescue treatments with infliximab (5mg/kg intravenously (iv) at week 0, 2, 6 and then every 8weeks), ciclosporin (iv 2mg/kg/daily and then oral 5mg/kg/daily) or tacrolimus (0.05mg/kg divided in 2 doses) in steroid-refractory moderate to severe UC patients from 7 Swiss and 1 Serbian tertiary IBD centers was retrospectively studied. The primary endpoint was the one year colectomy rate. RESULTS: 60% of patients responded to the first rescue therapy, 10% went to colectomy and 30% non-responders were switched to a 2(nd) line rescue treatment. 66% of patients responded to the 2(nd) line treatment whereas 34% failed, of which 15% went to colectomy and 19% received a 3(rd) line rescue treatment. Among those, 50% patients went to colectomy. Overall colectomy rate of the whole cohort was 18%. Steroid-free remission rate was 39%. The adverse event rates were 33%, 37.5% and 30% for the first, second and third line treatment respectively. CONCLUSION: Our data show that medical intervention even with 2(nd) and 3(rd) rescue treatments decreased colectomy frequency within one year of follow up. A longer follow-up will be necessary to investigate whether sequential therapy will only postpone colectomy and what percentage of patients will remain in long-term remission.

Microsatellite instability affecting the T17 repeats in intron 8 of HSP110, as well as five mononucleotide repeats in patients with colorectal carcinoma.

AIM: To investigate mononucleotide markers: BAT-25, BAT-26, NR-21, NR-22 and NR-24 in patients with colorectal cancer (CRC), and the status of HSP110T17, KRAS, BRAF and the MLH1 promoter mutations in microsatellite unstable CRC. METHODS: Genetic assessments were performed on samples obtained following resection of CRC in 200 patients. RESULTS: Allelic variations of HSP110T17 were found in all 18 patients with microsatellite instabilities (MSIs) in at least three markers (high-frequency MSI). By contrast, mutations of HSP110T17 were absent in all 20 patients with no MSI frequency. Eight out of 182 patients with low (instability in one marker) or no frequency MSI had allelic shifts due to polymorphisms of BAT-25 (1.5%), NR-21 (1.75%) and NR-24 (1.5%). BRAF mutations were associated with >5 bp shortening of HSP110T17. CONCLUSION: Patients with high-frequency MSI CRC had allelic variations of HSP110T17. BRAF mutations occur along with greater shortening in HSP110T17 during oncogenesis via the MSI pathway.

Autoimmune polyglandular syndrome type 2, alopecia universalis and Crohn's disease.

Autoimmune polyglandular syndromes are defined as a spectrum of association between 2 or more organ specific endocrinopaties and non-endocrine autoimmune diseases. Autoimmune polyglandular syndromes type 2 is characterized by the coexistence of adrenal failure with autoimmune thyroid disease and diabetes mellitus type 1. Inflammatory bowel diseases are rarely associated with these autoimmune disorders. Here, we report about a case of 33 years old male with known history of Crohn's colitis diagnosed in childhood. In 2003 the patient experienced sudden loss of hair, eyebrows, eyelashes, beard and body hair - alopecia universalis was diagnosed. At the age of 28, the patient was hospitalized with severe dehydration and clinical signs of ketoacidosis. Increased blood glucose (40 mmol/L), ketonuria and metabolic acidosis indicated diabetes mellitus type 1. In 2005, he had severe relapse of Crohn's disease and was treated with systemic corticosteroid. Although patient responded well to the induction therapy, fatigue, hypotension, bradycardia called for further investigations: free thyroxine - 6.99 pmol/L, thyroid-stimulating hormone >75 U/ml, anti-thyroid peroxidase antibodies >1000 U/mL, so diagnosis of Haschimoto thyroiditis was confirmed. Persistent hypotension and fatigue, recurrent hypoglycemic crises indicated a possible presence of hypo-function of adrenal glands. After complete withdrawal of corticosteroid therapy, low cortisol levels (69.4 nmol/L) and positive tetracosactide stimulation test proved adrenal cortex failure. Regardless of the intensive treatment for diabetes, hypothyroidism, adrenal insufficiency and Crohn's disease, it was extremely difficult to achieve and maintain control of all four diseases.

Clinical and pathological tools for identifying microsatellite instability in colorectal cancer.

AIM: To assess practical accuracy of revised Bethesda criteria (BGrev), pathological predictive model (MsPath), and histopathological parameters for detection of high-frequency of microsatellite instability (MSI-H) phenotype in patients with colorectal carcinoma (CRC). METHOD: Tumors from 150 patients with CRC were analyzed for MSI using a fluorescence-based pentaplex polymerase chain reaction technique. For all patients, we evaluated age, sex, family history of cancer, localization, tumor differentiation, mucin production, lymphocytic infiltration (TIL), and Union for International Cancer Control stage. Patients were classified according to the BGrev, and the groups were compared. The utility of the BGrev, MsPath, and clinical and histopathological parameters for predicting microsatellite tumor status were assessed by univariate logistic regression analysis and by calculating the sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values. RESULTS: Fifteen out of 45 patients who met and 4 of 105 patients who did not meet the BGrev criteria had MSI-H CRC. Sensitivity, specificity, PPV, and NPV for BGrev were 78.9%, 77%, 30%, and 70%, respectively. MSI histology (the third BGrev criterion without age limit) was as sensitive as BGrev, but more specific. MsPath model was more sensitive than BGrev (86%), with similar specificity. Any BGrev criterion fulfillment, mucinous differentiation, and right-sided CRC were singled out as independent factors to identify MSI-H colorectal cancer. CONCLUSION: The BGrev, MsPath model, and MSI histology are useful tools for selecting patients for MSI testing.

Terminal ileitis is not always Crohn's disease.

Chronic inflammation in the terminal ileum (TI) suggests a cause for the patient's symptoms, especially when the clinical suspicion is Crohn's disease (CD). Clinic, laboratory, endoscopic, histopathological evaluation of patients is required for the diagnosis of CD. The most frequent localization of CD is the TI. There are many other diseases affecting the TI. Non-steroidal antiinflammatory drug (NSAID) intake as well as other pathological conditions such as lymphoid hyperplasia, intestinal infections, lymphoma, infections and ulcerative colitis (UC) can mimic CD terminal ileitis. In this article the authors discuss these conditions, firstly in terms of differential diagnosis, and point out the facts that the clinicians must consider when they have a patient with terminal ileitis. Misdiagnosis of CD may be harmful to these patients because of inadequate response to therapy and occasionally an unnecessary operation may be performed. At the same time, the patients require appropriate treatment for their condition.

Prevalence and clinical impact of endoscopic pseudomembranes in patients with inflammatory bowel disease and Clostridium difficile infection.

BACKGROUND AND AIM: Limited data suggests that pseudomembranes are uncommon in patients with inflammatory bowel disease (IBD) and C. difficile associated disease (CDAD), but the reason for this is unknown. We aimed to evaluate the rate of pseudomembranes in this population, identify predictive factors for pseudomembranes' presence and assess its clinical impact. METHODS: This was a sub-study of a retrospective European Crohn's & Colitis Organization (ECCO) multi-center study on the outcome of hospitalized IBD patients with C. difficile. The present study included only patients who underwent lower endoscopy during hospitalization, and compared demographic and clinical parameters in the group of patients with discernable pseudomembranes versus those without. RESULTS: Out of 155 patients in the original cohort, 93 patients underwent lower endoscopy and constituted the study population. Endoscopic pseudomembranes were found in 12 (13%) of these patients. Patients with pseudomembranes presented more commonly with fever (p=0.02) compared to patients without pseudomembranes. No difference between the two groups was found with respect to the use of immunosuppressant drugs, background demographics or disease characteristics. Neither was there a difference between the group with or without pseudomembranes in the frequency of severe adverse clinical outcome or in the duration of hospitalization. On multi-variate analysis the presence of fever remained independently associated with the finding of pseudomembranes (OR 6, 95% CI 1.2-32, p=0.03). CONCLUSIONS: This study documents that hospitalized IBD patients with CDAD have low rate of endoscopic pseudomembranes, which is not accounted for by the use of immunosuppressant drugs. IBD patients with CDAD and discernable pseudomembranes more commonly present with fever, but their clinical outcome is similar to patients without pseudomembranes.

Combination immunomodulator and antibiotic treatment in patients with inflammatory bowel disease and clostridium difficile infection.

BACKGROUND & AIMS: Management of Clostridium difficile infection in patients with flaring inflammatory bowel disease (IBD) has not been optimized. We investigated the effects of combination therapy with antibiotics and immunomodulators in patients with IBD and C difficile infection. METHODS: We analyzed data from 155 patients (59% with ulcerative colitis [UC]) from a retrospective, European Crohn's and Colitis organization, multi-center study comparing outcome of hospitalized IBD patients with C difficile infection who were treated with antibiotics (n = 51) or antibiotics and immunomodulators (n = 104). The primary composite outcome was death or colectomy within 3 months of admission, in-hospital megacolon, bowel perforation, hemodynamic shock, or respiratory failure. RESULTS: The primary outcome occurred in 12% of patients given the combination treatment vs none of the patients given antibiotics alone (P = .01). UC, abdominal tenderness, or severe bloody diarrhea was more common among patients that received the combined therapy. However, multivariate analysis revealed that only the combination therapy maintained a trend for an independent association with the primary outcome (likelihood ratio = 11.9; CI, 0.9-157; P = .06). Treatment with 2 or 3 immunomodulators was correlated with the primary outcome, independent of disease severity at presentation (odds ratio [OR] = 17; CI, 3.2-91; P < .01). Acid-suppressing medications increased the risk of C difficile relapse (OR = 3.8; CI, 1.1-12.9; P = .03), whereas recent hospitalization correlated with increased rate of C difficile persistence (OR = 8; CI, 2.1-29; P = .002). CONCLUSIONS: Patients with IBD that also have C difficile infection are frequently treated with a combination of antibiotics and immunomodulators. However, this combination tends to associate with a worse outcome than antibiotic therapy alone. Prospective controlled trials are urgently needed to optimize the management of these challenging patients.

CARD15 gene polymorphisms in Serbian patients with Crohn's disease: genotype-phenotype analysis.

OBJECTIVE: Genetic heterogeneity and incomplete phenotype penetrance complicate genetic analysis of Crohn's disease (CD). Studies in western Europe have shown that CARD15 polymorphisms increase susceptibility to CD, but frequencies vary within different European populations. The aim here was to evaluate the prevalence of CARD15 mutations and their phenotypic correlation in a Serbian population. MATERIALS AND METHODS: 131 patients with CD, 65 patients with ulcerative colitis, and 88 healthy controls were genotyped for three common mutations (R702W, G908R, Leu1007insC) by PCR-restriction fragment length polymorphism. chi and Student's t-test were used for statistical assessment. RESULTS: At least one CARD15 disease-associated allele was found in 35.11% patients with CD, 14.77% of healthy controls (P=0.001), and 7.69% patients with ulcerative colitis (P=0.0001). The L1007fs mutation showed a significant association with CD (P<0.0001). The frequency of R702W mutant allele was almost equal in the control group and CD patients Univariate analyses established that CARD15 carriers had a significantly higher risk of isolated ileal location [P=0.042; odds ratio (OR) 2.30; 95% confidence interval (CI): 1.02-5.19], fibrostenotic behavior (P<0.0001; OR 9.86; 95% CI: 4.29-22.62), surgical resection (P=0.036; OR 2.2; CI, 1.046-4.626), and earlier onset of disease (P=0.026). CONCLUSION: This study confirms that CARD15 carriers, especially L1007fs mutants, in central Europeans have an increased risk of CD and it is associated with earlier onset, ileal, fibrostenotic disease and a higher risk of surgery. Any influence of latitude is not matched by an east-west divide on the genotype frequency and phenotype of CD within Europe.

Mechanism of diarrhea in microscopic colitis.

AIM: To search the pathophysiological mechanism of diarrhea based on daily stool weights, fecal electrolytes, osmotic gap and pH. METHODS: Seventy-six patients were included: 51 with microscopic colitis (MC) (40 with lymphocytic colitis (LC); 11 with collagenous colitis (CC)); 7 with MC without diarrhea and 18 as a control group (CG). They collected stool for 3 d. Sodium and potassium concentration were determined by flame photometry and chloride concentration by titration method of Schales. Fecal osmotic gap was calculated from the difference of osmolarity of fecal fluid and double sum of sodium and potassium concentration. RESULTS: Fecal fluid sodium concentration was significantly increased in LC 58.11+/-5.38 mmol/L (P<0.01) and CC 54.14+/-8.42 mmol/L (P<0.05) than in CG 34.28+/-2.98 mmol/L. Potassium concentration in LC 74.65+/-5.29 mmol/L (P<0.01) and CC 75.53+/-8.78 mmol/L (P<0.05) was significantly less compared to CG 92.67+/-2.99 mmol/L. Chloride concentration in CC 36.07+/-7.29 mmol/L was significantly higher than in CG 24.11+/-2.05 mmol/L (P<0.05). Forty-four (86.7%) patients had a secretory diarrhea compared to fecal osmotic gap. Seven (13.3%) patients had osmotic diarrhea. CONCLUSION: Diarrhea in MC mostly belongs to the secretory type. The major pathophysiological mechanism in LC could be explained by a decrease of active sodium absorption. In CC, decreased Cl/HCO3 exchange rate and increased chloride secretion are coexistent pathways.