Person surrounded by toilet paper, symbolizing chronic diarrhea

Chronic Diarrhea: Uncovering the Mystery of Microscopic Colitis

Elliot Brynn monogram
Elliot Brynn in Health & Wellness October 2026 • 3 min read.

"Is microscopic colitis the hidden cause of your persistent digestive issues? Learn about diagnosis, treatment, and when to seek expert help."


Microscopic colitis, a chronic inflammatory bowel disease, is increasingly recognized as a cause of persistent diarrhea. While less known than conditions like Crohn's disease or ulcerative colitis, its prevalence is on the rise, affecting individuals of all ages. Because its symptoms mimic those of irritable bowel syndrome (IBS), microscopic colitis often goes undiagnosed, leaving many to suffer unnecessarily.

This article aims to shed light on microscopic colitis, providing a comprehensive overview of its symptoms, diagnostic approaches, and treatment options. We'll explore when to suspect this condition, how it's diagnosed, and what steps you can take to manage it effectively. Whether you're experiencing chronic diarrhea yourself or seeking information for a loved one, this guide offers valuable insights into navigating the complexities of microscopic colitis.

It's crucial to remember that while this article provides informational content, it is not a substitute for professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of any medical condition.

AI Search Multiple angles on this topic

A Common Cause of Chronic Diarrhea

Microscopic colitis is recognized as a common cause of chronic diarrhea, although long-term outcome data remain limited. A 2021 institutional study searched pathology records from 2008 to 2018 and included patients with microscopic colitis or incomplete microscopic colitis. One reported meta-analysis estimated worldwide incidence at approximately 4.9 cases per 100,000 person-years for collagenous colitis and 5.0 for lymphocytic colitis. Diagnosis generally requires colonoscopy with biopsies because the relevant findings may not be apparent without tissue examination.

Why Biopsies Matter

Guidelines for chronic diarrhea address clinical assessment, exclusion of cancer or inflammation, and detection of disorders such as bile acid diarrhea, microscopic colitis, and lactose malabsorption. A 2024 hospital-based cohort study evaluated 116 patients with chronic diarrhea using histopathological examination of colonoscopic mucosal biopsies. Microscopic colitis can be underestimated when colonoscopy appears normal, making tissue sampling important even when the visible lining shows little or no abnormality. The diagnostic approach therefore depends on combining clinical assessment with biopsy-based evaluation rather than relying on endoscopic appearance alone.

From Invisible Disease to Histologic Diagnosis

Microscopic colitis is a chronic inflammatory condition of the colon that causes watery diarrhea while producing minimal or essentially normal endoscopic findings. Its diagnosis therefore relies on histopathology. Histologic classification recognizes two subtypes: lymphocytic colitis and collagenous colitis. Lymphocytic colitis is characterized by more than 20 intraepithelial lymphocytes per 100 epithelial cells.

When Should You Suspect Microscopic Colitis?

Person surrounded by toilet paper, symbolizing chronic diarrhea

If you experience persistent, watery diarrhea, especially at night, accompanied by abdominal cramps and potential weight loss, it's essential to consider microscopic colitis. The hallmark of this condition is watery stool consistency, which can sometimes lead to fecal incontinence, significantly impacting your quality of life. Women over 50 are particularly susceptible, but it can affect anyone.

Certain factors can increase your risk of developing microscopic colitis. These include:

  • Medications: Proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), nonsteroidal anti-inflammatory drugs (NSAIDs), Acarbose, Ranitidine, and Ticlopidine.
  • Autoimmune disorders: Rheumatoid arthritis, thyroid diseases, diabetes, and celiac disease.
AI Search Multiple angles on this topic

Limits of Maintenance Evidence

Evidence concerning budesonide maintenance in microscopic colitis includes a population-based cohort with longitudinal follow-up. The study authors identified its relatively small sample size as a limitation. They also described the population-based design and longitudinal follow-up as strengths. These features mean that the findings offer useful real-world observations but should be interpreted with attention to the study's limited sample size.

Microscopic Colitis Versus IBS

Microscopic colitis typically causes chronic, nonbloody, watery diarrhea and is more common in people older than 50 and in women. It may resemble other causes of chronic diarrhea because the colon can look normal during colonoscopy, whereas biopsies can reveal the condition. European guideline evidence found that after 6 to 8 weeks of treatment, 81% of patients receiving budesonide 9 mg per day achieved a clinical response, compared with 36% receiving placebo.

If you have these risk factors, it's even more important to discuss your symptoms with a doctor to determine if further investigation is needed.

Seeking Expert Guidance

Navigating the complexities of microscopic colitis requires the expertise of healthcare professionals. If you have questions or concerns about this condition, don't hesitate to reach out to your doctor or a gastroenterologist. They can provide personalized advice, accurate diagnosis, and effective treatment strategies to help you manage your symptoms and improve your quality of life.

AI Search Multiple angles on this topic

Improving Epidemiology and Treatment

Recent epidemiologic studies and randomized therapeutic trials have improved understanding of microscopic colitis, which commonly presents with debilitating chronic watery diarrhea. Nonsteroidal anti-inflammatory drugs, proton pump inhibitors, and antidepressants have traditionally been considered major risk factors. Current descriptions also identify smoking as a risk factor and budesonide as an effective treatment. Future progress will depend on refining risk-factor evidence and expanding treatment options for patients whose disease remains difficult to manage.

An Invisible, Disabling Illness

A case report described a frail 92-year-old woman with dementia who had experienced a year of chronic watery, non-bloody diarrhea. Her symptoms included abdominal bloating, weight loss, fecal urgency, nocturnal stools, and fecal incontinence. Flexible sigmoidoscopy appeared macroscopically normal, but tissue examination demonstrated microscopic colitis. The case illustrates how an apparently normal endoscopic examination can coexist with substantial effects on daily life and quality of life.

What tissue examination adds to visible findings

Microscopic colitis can produce substantial bowel symptoms even when the colon looks normal or nearly normal during endoscopy. The diagnosis depends on the distinct tissue changes, rather than appearance alone.[1]

Reduced AQP8 expression has also been observed in other diarrheal disorders, so that finding is not specific to microscopic colitis. Its reversal with budesonide offers a possible explanation for the drug’s antidiarrheal effect, rather than proof that this is the only mechanism involved.[2]

How biopsy and treatment findings compare

A review of non-budesonide therapies reported a high response rate for bismuth subsalicylate, but the studies varied in how they defined response and remission. That inconsistency may have inflated the apparent benefit, so the estimate is less straightforward to compare across studies.[3]

Reported prevalence among people with chronic watery, nonbloody diarrhea differs across sources: a Spanish study reported 31.9%, while a pooled European guideline estimate was 12.8%. The pooled estimate itself reflects marked variation by geography, population background, case definitions, and pre-colonoscopy workup.[4]

What remains uncertain in microscopic colitis evidence

  • How reliably can treatment benefits be compared when studies use differing definitions of clinical response and remission?[3]
  • How much do setting and diagnostic workup account for the wide variation in reported prevalence among people with chronic watery diarrhea?[4]
  • Would fecal calprotectin perform similarly outside the specific group and study in which its diagnostic characteristics were reported?[4]

Terms used in microscopic colitis

AQP8
AQP8 expression is discussed in relation to diarrheal disorders.[2]

Sources

  1. European guidelines on microscopic colitis: United European Gastroenterology and European Microscopic Colitis Group statements and recommendations (pmc.ncbi.nlm.nih.gov)
  2. Budesonide as induction therapy for incomplete microscopic colitis: A randomised, placebo‐controlled multicentre trial (pmc.ncbi.nlm.nih.gov)
  3. Effectiveness of Non-Budesonide Therapies in Management of Microscopic Colitis: A Systematic Review and Meta-analysis. (pubmed.ncbi.nlm.nih.gov)
  4. Chronic Diarrhea Owing to Microscopic Colitis: A Cohort Study with Insights into Diagnostic Challenges and Size of the Problem (pmc.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What exactly is microscopic colitis and why is it important to know about it?

Microscopic colitis is a chronic inflammatory bowel disease that's becoming more recognized as a cause of ongoing diarrhea. While it shares symptoms with Irritable Bowel Syndrome (IBS), it is distinct and can be diagnosed through specific tests. It's important because, unlike IBS, microscopic colitis involves inflammation in the colon that can be seen under a microscope. This distinction is crucial for proper treatment.

2

What are the main symptoms of microscopic colitis?

The primary symptom of microscopic colitis is persistent, watery diarrhea, often accompanied by abdominal cramps. Some people might also experience fecal incontinence and weight loss. The specific nature of the diarrhea, especially if it's watery and persistent, is a key indicator that differentiates microscopic colitis from other conditions with similar symptoms, like IBS.

3

Are there any risk factors that make someone more likely to develop microscopic colitis?

Several factors can increase your risk of developing microscopic colitis. Certain medications, such as proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), and nonsteroidal anti-inflammatory drugs (NSAIDs) have been linked to the condition. Additionally, having autoimmune disorders like rheumatoid arthritis, thyroid diseases, diabetes, and celiac disease can also elevate your risk. Recognizing these factors is important for early detection and management.

4

How is microscopic colitis diagnosed?

Diagnosis of microscopic colitis typically involves a colonoscopy with biopsies. During the colonoscopy, a doctor examines the colon for any visible abnormalities. However, in microscopic colitis, the colon often appears normal to the naked eye. The diagnosis is confirmed by taking small tissue samples (biopsies) and examining them under a microscope to look for specific signs of inflammation. This microscopic examination is essential for distinguishing microscopic colitis from other conditions.

5

What should I do if I think I might have microscopic colitis?

If you suspect you have microscopic colitis, it's important to consult with your doctor or a gastroenterologist. They can evaluate your symptoms, assess your risk factors, and perform the necessary tests to confirm the diagnosis. Seeking expert guidance ensures you receive the appropriate treatment and management strategies to improve your digestive health and overall quality of life. They may recommend dietary changes or medications.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.