Incidence Of Lymphocytic Colitis Research Articles

The Epidemiology of Microscopic Colitis in Olmsted County, Minnesota: Population-Based Study From 2011 to 2019

Epidemiologic studies from Europe and North America have reported an increasing incidence of microscopic colitis (MC) in the late 20th century, followed by a plateau. This population-based study assessed recent incidence trends and the overall prevalence of MC over the past decade. Residents of Olmsted County, MN, diagnosed with collagenous colitis (CC) or lymphocytic colitis (LC) between January 1, 2011, and December 31, 2019 were identified using the Rochester Epidemiology Project. Clinical variables were abstracted by chart review. Incidence rates were age- and sex-adjusted to the 2010 US population. Associations between incidence and age, sex, and calendar periods were evaluated using Poisson regression analyses. A total of 268 incident cases of MC were identified with a median age at diagnosis of 64 years (range, 19-90 y); 207 (77%) were women. The age- and sex-adjusted incidence of MC was 25.8 (95% CI, 22.7-28.9) cases per 100,000 person-years. The incidence of LC was 15.8 (95% CI, 13.4-18.2) and CC was 9.9 (95% CI, 8.1-11.9) per 100,000 person-years. A higher MC incidence was associated with increasing age and female sex (P < .01). There was no significant trend in age- and sex-adjusted incidence rate over the study period (P= .92). On December 31, 2019, the prevalence of MC, LC, and CC (including cases diagnosed before 2011) was 246.2, 146.1, and 100.1 per 100,000 persons, respectively. The incidence of MC and its subtypes was stable between 2011 and 2019, but its prevalence was higher than in previous periods. The incidence of MC continues to be associated with increasing age and female sex.

Microscopic colitis: a population-based case series over a 9-year period in Northern Ireland.

We report clinicopathological experience of microscopic colitis (MC) in a population-based case series in Northern Ireland over a 9-year period. The pathology laboratory information system within a large teaching centre serving two healthcare trusts was interrogated for cases coded between 2008 and 2016 as collagenous colitis (CC) or lymphocytic colitis (LC). Demographic, clinical and follow-up information was collected from healthcare records. A total of 326 new diagnoses of MC were identified, an average annual incidence of 6.7 per 100 000 population. The average annual incidence of CC and LC was 5.0 and 1.7 per 100 000 population, respectively. For coding reasons it is likely that LC data are incomplete. Of 191 cases diagnosed by specialist gastrointestinal pathologists, 141 patients had CC and 50 patients had LC. Both CC and LC predominantly involved women aged 60-79. Some 15% demonstrated endoscopic abnormalities. Endoscopic sampling protocols varied widely: 30% of individuals with CC and 32% of those with LC had the right and left colon sampled separately, with histology concordant in 95% of cases. Of the 191 cases, only one case (of LC) was refractory to treatment; the rest exhibited a clinical response. Only 35 patients had follow-up endoscopy and biopsies, and three of each diagnosis showed persistent disease on histology. Overall, CC and LC are benign conditions with similar demographics, clinical associations, management and outcomes. Separate sampling of the right and left colon is advised at colonoscopy if this diagnosis is being considered, but left colonic sampling, which can be performed at flexible sigmoidoscopy, will diagnose the vast majority of cases.

Novel Use of Budesonide MMX in the Treatment of Lymphocytic Colitis

Background: Microscopic colitis, in particular, lymphocytic colitis is a relatively common cause of chronic diarrhea. The incidence of lymphocytic colitis is reported up to 63.7 per 100,000 person-years. Unfortunately, limited pharmacologic interventions are available with durable remission. We present a case of lymphocytic colitis refractory to conventional therapy with efficacy with budesonide MMX therapy. Case Presentation: A 60-year-old Caucasian retired Army service member presented to a civilian Gastroenterology clinic with complaint of chronic diarrhea. He reported having up to 6-8 liquid bowel movements per day with Bristol 5-6 consistency for over 4 months with an associated 10 pound weight loss. He was initially discontinued on esomeprazole therapy and started on loperamide with no improvement in symptoms after 4 weeks. He was started on bismuth subsalicylate for another 4 weeks with minimal to no response. He attempted a short course of oral prednisone therapy but was intolerant due to significant side effects including headaches and migraines. He underwent an EGD and repeat colonoscopy for second opinion evaluation. Random duodenal biopsies were negative for enteritis (to include celiac) and repeat colonic biopsies with persistent lymphocytic colitis but negative for infectious agents and/or inflammatory bowel disease. Patient was started on budesonide MMX therapy daily for 2 months. He noted complete resolution of symptoms with normalization of bowels within 1 week of therapy. He remained asymptomatic at follow-up 3 months after therapy completion. Discussion: Lymphocytic colitis is a common colonic disorder associated with chronic watery diarrhea. When medication side effects and food-related diarrhea is eliminated, pharmacological options are limited with short rates of durable remission. Budesonide MMX is a novel therapy option due to its formulation and colonic delivery design allowing high rates of colonic penetration with minimal systemic absorption.

The Temporal Evolution of Histological Abnormalities in Microscopic Colitis

Microscopic colitis (MC) is a common cause of chronic watery diarrhoea but long-term follow-up data are sparse. We performed a retrospective review of health records and all pathology reports in a regional cohort of patients with MC to describe the change in pre- and post-diagnostic colon biopsies. MC was diagnosed in 468 patients with collagenous colitis (CC), 361 with lymphocytic colitis (LC) and 226 with incomplete MC (MCi). The 2014 incidence of CC, LC and MCi was 14.5, 14.9 and 5 per 10(5). Biopsies from both right and left colon were obtained in 237 (51%) patients with CC, 200 (55%) with LC and 107 (47%) with MCi. The diagnostic sensitivities of both left- and right-sided biopsies for MC were high and did not differ. Pre-diagnostic biopsies were obtained in 150 patients and lamina propria inflammation was described in 59, 47 and 43% of patients with a diagnosis of CC, LC and MCi respectively within 1 year, while histology was normal in 16, 13 and 21%. Post-diagnostic biopsies were obtained in 283 patients. MC persisted for up to one year in 77% with CC, 64% with LC and 45% with MCi, of whom 6, 9 and 18% respectively changed to a different MC subgroup. Colonic biopsies obtained prior to the MC diagnosis often revealed increased lamina propria inflammation. The pathological changes of CC and LC are more persistent than those of MCi. Biopsies from the descending or sigmoid colon are sufficient to elucidate whether a patient with chronic watery diarrhoea has MC.

Turning off the Faucet: Novel Therapy for Lymphocytic Colitis

Background: Microscopic colitis, in particular, lymphocytic colitis is a relatively common cause of chronic diarrhea. The incidence of lymphocytic colitis is reported up to 63.7 per 100,000 person-years. Unfortunately, limited pharmacologic interventions are available with durable remission. We present a case of lymphocytic colitis refractory to conventional therapy with efficacy with budesonide MMX therapy. Case Presentation: A 60-year-old Caucasian retired Army service member presented to a civilian Gastroenterology clinic with complaint of chronic diarrhea. He had an associated history of GERD and hemochromatosis. He reported having up to 6-8 liquid bowel movements per day with Bristol 5-6 consistency for over 4 months. He reported having associated mild weight loss of 10 pounds. He reported no exacerbation of symptoms with lactose products and/or gluten-containing products. He underwent a colonoscopy with reports demonstrating a normal mucosal appearance but with random biopsies consistent with lymphocytic colitis. He was initially discontinued on esomeprazole therapy and started on loperamide with no improvement in symptoms after 4 weeks. He was started on bismuth subsalicylate for another 4 weeks with minimal to no response. He attempted a short course of oral prednisone therapy but was intolerant due to significant side effects including headaches and migraines. He underwent an EGD and repeat colonoscopy for second opinion evaluation. Random duodenal biopsies were negative for enteritis (to include celiac) and repeat colonic biopsies with persistent lymphocytic colitis but negative for infectious agents and/or inflammatory bowel disease (Figures 1,2). All specimens were reviewed by a gastro-pathologist.Figure 1Figure 2Patient was started on budesonide MMX therapy daily for 2 months. He noted complete resolution of symptoms with normalization of bowels within 1 week of therapy. He remained asymptomatic at followup 3 months after therapy completion. Discussion: Lymphocytic colitis is a common colonic disorder associated with chronic watery diarrhea. When medication side effects and food-related diarrhea is eliminated, pharmacological options are limited with short rates of durable remission. Budesonide MMX is a novel therapy option due to its formulation and colonic delivery design allowing high rates of colonic penetration with minimal systemic absorption.

The epidemiology of microscopic colitis: a 10-year pathology-based nationwide Danish cohort study

Objective. Microscopic colitis (MC) includes two main types: collagenous colitis (CC) and lymphocytic colitis (LC). Previous studies have indicated an increasing incidence, but these have mainly been based on regional databases. We found it important to study the epidemiology based on a comprehensive nationwide cohort. Material and methods. We studied the epidemiological data of MC in Denmark from 2002 to 2011. The cohort consisted of all patients with a recorded diagnosis of either CC or LC in the Danish Pathology Register during the study period. Data on all patients with a registered colon biopsy were also included. Results. A total of 7777 patients, 4749 (61%) with CC and 3028 (39%) with LC, were identified. Over the study period, the annual incidence of diagnosed cases of CC increased from 2.9/105 to 14.9/105 and of LC from 1.7/105 to 9.8/105. In 2011, the incidence of MC was 24.7/105 inhabitants. The age-specific incidence showed that the risk of both CC and LC increased with age. The female/male ratio, distribution of the type of colitis and mean age at diagnosis were relatively stable during the study period. The annual number of registered colon biopsies in the pathology register increased from 21.583 in 2002 to 39.733 in 2011, indicating an increased diagnostic activity. Conclusion. In a nationwide cohort study, the incidence of CC and LC continued to increase from 2002 to 2011. An increased diagnostic activity could in part explain the increase in the number of diagnosed cases.

The Epidemiology of Microscopic Colitis in Olmsted County From 2002 to 2010: A Population-Based Study

The increasing incidence of microscopic colitis has been partly attributed to detection bias. We aimed to ascertain recent incidence trends and the overall prevalence of microscopic colitis in a population-based study. Using data from the Rochester Epidemiology Project, we identified residents of Olmsted County, Minnesota, who were diagnosed with collagenous colitis or lymphocytic colitis from January 1, 2002, through December 31, 2010, based on biopsy results and the presence of diarrhea (N = 182; mean age at diagnosis, 65.8 years; 76.4% women). Poisson regression analyses were performed to evaluate associations between incidence and age, sex, and calendar period. The age- and sex-adjusted incidence of microscopic colitis was 21.0 cases per 100,000 person-years (95% confidence interval [CI], 18.0-24.1 cases per 100,000 person-years). The incidence of lymphocytic colitis was 12.0 per 100,000 person-years (95% CI, 9.6-14.3 per 100,000 person-years) and collagenous colitis was 9.1 per 100,000 person-years (95% CI, 7.0-11.1 per 100,000 person-years). The incidence of microscopic colitis and its subtypes remained stable over the study period (P = .63). Increasing age (P < .001) and female sex (P < .001) were associated with increasing incidence. On December 31, 2010, the prevalence of microscopic colitis was 219 cases per 100,000 persons (90.4 per 100,000 persons for collagenous colitis and 128.6 per 100,000 persons for lymphocytic colitis). The incidence of microscopic colitis in Olmsted County residents has stabilized and remains associated with female sex and increasing age.

Stable Incidence of Collagenous Colitis and Lymphocytic Colitis in Örebro, Sweden, 1999–2008

The incidence of microscopic colitis (MC) has increased in several centers, but long-term epidemiologic data are missing. We report an epidemiologic study of collagenous colitis (CC) and lymphocytic colitis (LC) during 1999-2008, as a follow-up of our previous studies 1984-1998. Population-based study of residents of the catchment area of the hospital, with a new diagnosis of MC between 1999 and 2008. Patients were identified by diagnosis registers of the Departments of Medicine and Pathology. Medical files were reviewed, and colonic biopsies were reevaluated. Collagenous colitis was diagnosed in 96 patients (75 females) and LC in 90 patients (74 females). The mean annual age-standardized incidence (per 100,000 inhabitants) was MC 10.2 (95% confidence interval: 8.7-11.7), CC 5.2 (4.2-6.3), and LC 5.0 (4.0-6.0). Age-specific incidence showed a peak in females older than 70 years. Prevalence (per 100,000 inhabitants) on December 31, 2008, was MC 123 (107.6-140.0), CC 67.7 (56.4-80.6), and LC 55.3 (45.2-67.1). A comparison of current study period with 1993-1998 showed unchanged mean incidence of MC, but a 2-fold increase in women older than 60 years with LC (standardized rate ratios 2.2, [1.2-3.7]) and increased female to male ratio (4.6:1 versus 2.1:1; P = 0.02) in LC. After an initial rise during 1980s and early 1990s, annual incidence of CC and LC has been stable during the last 15 years around 5/100,000 inhabitants for each disorder. The increasing incidence in older women with LC may be related to an increasing proportion of older individuals in the background population and increased colonoscopy frequency in elderly.

Mo1354 Epidemiology of Microscopic Colitis - A 10-Year Nationwide Danish Cohort Study

Background Microscopic colitis includes: collagenous colitis (CC) and lymphocytic colitis (LC). European and North American studies have investigated the epidemiology of microscopic colitis and found an increasing incidence from 1990 2000. A study from US indicated a combined annual incidence of microscopic colitis of 19.7/100.000. Previous studies are mainly based on regional registries and we found it of interest to study the epidemiology based on a comprehensive nationwide data. Aims The aim of the study was to estimate the development in the incidence and demography of microscopic colitis in Denmark from 2002-2011 based on Danish national registries. Methods This registry study was based on the datasets covering the entire Danish population of around 5.4 mio. inhabitants. The cohort consisted of all patients with a first time recorded diagnosis of either CC or LC in the Danish Pathology Register from January 2002 to December 2011. This register was established in 1990 and in 1997 it became a legal obligation for all departments of pathology in Denmark to report all pathology data statements and the diagnoses were coded according to a Danish version of the Systematized Nomenclature of Medicine (SNOMED). The data is used by the pathologists in the daily diagnostic process and covers all pathology data in Denmark. Results The cohort consisted of a total of 7.777 patients, hereof 4.749 (61%) with CC and 3.028 (39%) with LC. In the 10-year period the annual incidence of diagnosed cases of CC increased from 2.9/100.000 to 14.9/100.000 and of LC from 1.7/100.000 to 9.8/100.000. Fig 1.The female:male ratio was 3:1 for CC and 1.8:1for LC. The mean age at diagnosis was 67 years for CC and 64 years for LC. There was no change in the distribution between CC and LC, the female:male ratio or the age of diagnosis during the 10-year period. The annual number of persons with registered colon-biopsies in the pathology register increased from 21.583 in 2002 to 39.733 in 2011 indicating an increased diagnostic activity. Conclusions In this nationwide cohort study the incidence of CC and LC was increasing in a ten-year period from 2002 to 2011. A combined incidence of microscopic colitis of 24.7/ 100.000 in 2011 was found. There was no change in the distribution of type, gender or age at diagnosis in the period. An increased diagnostic activity could explain the increase of diagnosed cases.

P627 Peripheral mesenteric vein thromboses are frequently found in IBD patients and are associated with intestinal surgery in Crohn's disease

Background Microscopic colitis includes: collagenous colitis (CC) and lymphocytic colitis (LC). European and North American studies have investigated the epidemiology of microscopic colitis and found an increasing incidence from 1990 2000. A study from US indicated a combined annual incidence of microscopic colitis of 19.7/100.000. Previous studies are mainly based on regional registries and we found it of interest to study the epidemiology based on a comprehensive nationwide data. Aims The aim of the study was to estimate the development in the incidence and demography of microscopic colitis in Denmark from 2002-2011 based on Danish national registries. Methods This registry study was based on the datasets covering the entire Danish population of around 5.4 mio. inhabitants. The cohort consisted of all patients with a first time recorded diagnosis of either CC or LC in the Danish Pathology Register from January 2002 to December 2011. This register was established in 1990 and in 1997 it became a legal obligation for all departments of pathology in Denmark to report all pathology data statements and the diagnoses were coded according to a Danish version of the Systematized Nomenclature of Medicine (SNOMED). The data is used by the pathologists in the daily diagnostic process and covers all pathology data in Denmark. Results The cohort consisted of a total of 7.777 patients, hereof 4.749 (61%) with CC and 3.028 (39%) with LC. In the 10-year period the annual incidence of diagnosed cases of CC increased from 2.9/100.000 to 14.9/100.000 and of LC from 1.7/100.000 to 9.8/100.000. Fig 1.The female:male ratio was 3:1 for CC and 1.8:1for LC. The mean age at diagnosis was 67 years for CC and 64 years for LC. There was no change in the distribution between CC and LC, the female:male ratio or the age of diagnosis during the 10-year period. The annual number of persons with registered colon-biopsies in the pathology register increased from 21.583 in 2002 to 39.733 in 2011 indicating an increased diagnostic activity. Conclusions In this nationwide cohort study the incidence of CC and LC was increasing in a ten-year period from 2002 to 2011. A combined incidence of microscopic colitis of 24.7/ 100.000 in 2011 was found. There was no change in the distribution of type, gender or age at diagnosis in the period. An increased diagnostic activity could explain the increase of diagnosed cases.

Systematic review: are lymphocytic colitis and collagenous colitis two subtypes of the same disease ‐ microscopic colitis?

Despite similar clinical symptoms, collagenous colitis (CC) and lymphocytic colitis (LC) are considered two distinct disease entities. To compare pathoanatomical findings, clinical presentations, risk factors, course of diseases and response to treatment in CC and LC to establish whether they could be subtypes of the same disease, microscopic colitis (MC). The MEDLINE was searched for CC, LC and MC, and clinical studies of >20 patients were included. Pooled results with 95% confidence intervals were calculated based on the number of patients. An abnormal number of intraepithelial lymphocytes are found in 45% (40-50%) with CC, and an abnormal subepithelial collagen band in 16% (13-20%) with LC suggesting a histological overlap. The incidence of CC and LC has increased in parallel. Mean age (CC 63 years; LC 60 years) and clinical presentation are indistinguishable, and females are predominant in CC (77%; 75-79%) as well as LC (68%; 66-70%). Risk factors such as nonsteroid anti-inflammatory drugs consumption CC 39% (36-42%); LC 32% (29-35%) are similar and prevalence of concomitant autoimmune diseases such as coeliac disease (CC 5%; CI: 4-6% and LC 7%; CI: 6-9%) do not differ. Bile acid diarrhoea is highly prevalent in CC (41%; 37-45%) and LC (29%; 24-34%). The effect of budesonide is identical. CC and LC could be considered histological subtypes of the same disease, MC. To facilitate recruitment to clinical trials, all MC patients could be included in future trials and stratified for subtypes.

PTU-112 Presentation, treatment and clinical outcome of collagenous and lymphocytic colitis over a 6-year period in a single UK centre

IntroductionCollagenous colitis (CC) and lymphocytic colitis (LC) are referred to collectively as microscopic colitis (MC). CC and LC represent an increasingly common cause of chronic diarrhoea. However, clinical and epidemiological...

Evolution of the incidence of collagenous colitis and lymphocytic colitis in Terrassa, Spain: A population-based study

Previous studies suggest an increase in the incidence rate of microscopic colitis in recent decades. The aim was to evaluate changes in the population-based incidence rate of microscopic colitis and its subtypes over time in Terrassa, Spain. This was a prospective study during the period 2004-2008, with a comparison of data from the period 1993-1997. The catchment area was a mixed rural-urban type, with nearly 290,000 inhabitants. All patients with nonbloody chronic diarrhea referred for a diagnostic colonoscopy were included. Multiple biopsy specimen samples were obtained when the macroscopic appearance of the colonic mucosa was normal to rule out microscopic colitis. Crude and adjusted incidence rates based on either the year of diagnosis or the date of onset of symptoms were calculated. Forty patients with collagenous colitis (CC) and 32 with lymphocytic colitis (LC) were identified. The mean annual incidence of CC and LC based on the year of onset of symptoms was 2.6/10(5) inhabitants (95% confidence interval [CI], 1.9-3.3), and 2.2/10(5) inhabitants (95% CI, 1.5-3.0), respectively. Incidence rates for CC based on the year of onset of symptoms were significantly higher in the period 2004-2008 than in 1993-1997 (2.6 versus 1.1/10(5) ; P = 0.012). The increase in CC incidence was more marked in women (P = 0.047) than in men (P = 0.19). The annual incidence of CC in Terrassa increased over time, mainly in women. Nevertheless, the rates were much lower than those observed in northern Europe, suggesting that there is a north-south difference in the incidence of microscopic colitis.

Microscopic Colitis in Routine Colonoscopies

Lymphocytic colitis (LC) and collagenous colitis (CC), both known as microscopic colitis (MC), are uncommon entities with increasing incidence as more clinicians take biopsies from macroscopically normal colons and as pathologists use more rigorous diagnostic criteria to be confident of the diagnosis. Information on the incidence of this type of colitis is limited and based on reported cases. The purpose of this work is to estimate the incidence of LC and CC in reviewed routine colonoscopies. We reviewed 2815 colonoscopies performed at a tertiary referral center with an open-access service using restricted histological criteria in order to establish the frequency rate of LC and CC in routine colonoscopic biopsy material. Cases suspicious for MC were stained with Masson's trichrome or Congo red stain and immunohistochemically for lymphocytes, where appropriate. Review of routine colonoscopic biopsies showed that MC is underreported in our colonoscopic material. Incidence rates of LC and CC (0.9 and 0.4, respectively) were based on morphological assessment of colonoscopic biopsies using stringent criteria together with clinical data and after differentiation with other lesions which can mimic MC. The 10.2% rate of this type of colitis in patients with chronic watery diarrhea indicates the necessity to consider these lesions in older individuals with diarrhea and normal endoscopical colonic mucosa.

Incidence of collagenous and lymphocytic colitis: a 5-year population-based study.

The incidence of collagenous and lymphocytic colitis is not well known. We sought to assess the incidence of collagenous and lymphocytic colitis in a well-defined population during a 5-yr study period. From January 1, 1993, to December 31, 1997, all new patients diagnosed with collagenous or lymphocytic colitis living in the catchment area of the Hospital Mutua de Terrassa (Barcelona, Spain) were identified. Since 1993 all patients with chronic diarrhea were referred for a diagnostic colonoscopy. Multiple biopsy sampling of the entire colon was performed when appearance of the colonic mucosa was grossly normal. Twenty-three cases of collagenous colitis and 37 of lymphocytic colitis were diagnosed. The female:male ratios were 4.75:1 and 2.7:1 for collagenous and lymphocytic colitis, respectively. The mean age at onset of symptoms was 53.4+/-3.2 (range, 29-82) yr for collagenous colitis, and 64.3+/-2.7 (range, 28-87) yr for lymphocytic colitis (p = 0.012). The mean annual incidence per 100,000 inhabitants based on the year of onset of symptoms was 1.1 (95% confidence interval [CI], 0.4-1.7) for collagenous colitis, and 3.1 (95% CI, 2.0-4.2) for lymphocytic colitis. A peak incidence was observed in older women in both diseases. A rate of microscopic colitis of 9.5 per 100 normal-looking colonoscopies performed in patients with chronic watery diarrhea was observed. Normal rectal biopsies were found in 43 % and 8% of patients with collagenous and lymphocytic colitis, respectively. The incidence of lymphocytic colitis is three times higher than that of collagenous colitis. Microscopic colitis should be considered as a major possibility in the work-up of chronic diarrhea in older women.

Incidence of collagenous and lymphocytic colitis: a 5-year population-based study

Objective: The incidence of collagenous and lymphocytic colitis is not well known. We sought to assess the incidence of collagenous and lymphocytic colitis in a well-defined population during a 5-yr study period. Methods: From January 1, 1993, to December 31, 1997, all new patients diagnosed with collagenous or lymphocytic colitis living in the catchment area of the Hospital Mútua de Terrassa (Barcelona, Spain) were identified. Since 1993 all patients with chronic diarrhea were referred for a diagnostic colonoscopy. Multiple biopsy sampling of the entire colon was performed when appearance of the colonic mucosa was grossly normal. Results: Twenty-three cases of collagenous colitis and 37 of lymphocytic colitis were diagnosed. The female:male ratios were 4.75:1 and 2.7:1 for collagenous and lymphocytic colitis, respectively. The mean age at onset of symptoms was 53.4 ± 3.2 (range, 29–82) yr for collagenous colitis, and 64.3 ± 2.7 (range, 28–87) yr for lymphocytic colitis ( p = 0.012). The mean annual incidence per 100,000 inhabitants based on the year of onset of symptoms was 1.1 (95% confidence interval [CI], 0.4–1.7) for collagenous colitis, and 3.1 (95% CI, 2.0–4.2) for lymphocytic colitis. A peak incidence was observed in older women in both diseases. A rate of microscopic colitis of 9.5 per 100 normal-looking colonoscopies performed in patients with chronic watery diarrhea was observed. Normal rectal biopsies were found in 43% and 8% of patients with collagenous and lymphocytic colitis, respectively. Conclusions: The incidence of lymphocytic colitis is three times higher than that of collagenous colitis. Microscopic colitis should be considered as a major possibility in the work-up of chronic diarrhea in older women.