A 56-year-old woman comes to the office for evaluation of chronic diarrhea. The patient began experiencing daily watery bowel movements several months ago and tried eliminating dairy products, but the diarrhea continued to worsen. Lately, she has been having 5-6 bowel movements daily and occasionally at night. The patient has had no melena, hematochezia, fever, abdominal pain, nausea, vomiting, or weight loss but does have fecal urgency. Medical history is significant for obesity, hypertension, and knee osteoarthritis. Home medications include hydrochlorothiazide and naproxen. She drinks a glass of wine with dinner daily but does not smoke cigarettes. Vital signs are within normal limits. The abdomen is nondistended, soft, and nontender with no organomegaly. Bowel sounds are normoactive. Stool testing for occult blood is negative. Colonoscopy reveals a normal-appearing colon. Random colonic biopsies demonstrate mononuclear cell infiltration of the lamina propria and a thickened subepithelial collagen band. Which of the following is the most likely diagnosis?
Microscopic colitis | |
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NSAIDs = nonsteroidal anti-inflammatory drugs; PPIs = proton pump inhibitors; SSRIs = selective serotonin reuptake inhibitors. | |
This patient most likely has microscopic colitis (MC), an immune-mediated colitis characterized by watery, nonbloody diarrhea. MC is a secretory diarrhea and, unlike osmotic diarrhea, may occur during periods of fasting and/or at night. Other symptoms can include fecal urgency, incontinence, abdominal pain, fatigue, and weight loss. Blood and stool studies are usually unremarkable (eg, normal C-reactive protein and hemoglobin, negative fecal occult blood test). The diagnosis is confirmed with colonoscopy and biopsy; although the colon appears grossly normal, biopsy of the mucosa reveals a mononuclear inflammatory infiltrate within the lamina propria. The disease is divided histologically into 2 types:
MC is likely due to an abnormal immune response to various gastrointestinal and external agents. Certain medications—including nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors, and selective serotonin reuptake inhibitors—have been associated with the development of MC, as has smoking. Those with other autoimmune conditions (eg, celiac disease, autoimmune thyroiditis) are at increased risk. Older women (age >60) are disproportionately affected.
Initial management of MC includes smoking cessation and withdrawal of triggering medications. If diarrhea persists, budesonide and antidiarrheal medications (eg, loperamide) can be considered.
(Choice A) Clostridioides difficile infection can cause chronic diarrhea but is typically associated with fever. In addition, colonoscopy is expected to demonstrate bowel wall edema, erythema, and pseudomembranes (white plaques).
(Choice B) Crohn disease can cause chronic diarrhea; however, patients typically have abdominal pain, systemic symptoms (eg, fatigue), and perianal disease (eg, fissures), and stool guaiac testing is often positive. Colonoscopy demonstrates intermittent ulcerations (cobblestone appearance), and histology reveals transmural ulcerations and granulomas.
(Choice C) Diarrhea-predominant irritable bowel syndrome is associated with chronic diarrhea but is typified by recurrent abdominal pain. Additionally, colonoscopy and histology are normal.
(Choice D) Factitious diarrhea (ie, laxative abuse) is more common in women; however, endoscopy commonly demonstrates melanosis coli (brown discoloration of the colon). Collagen bands are more consistent with MC.
Educational objective:
Microscopic colitis disproportionately affects women age >60 and is characterized by chronic, watery diarrhea that may occur during periods of fasting and/or at night. Colonoscopy reveals grossly normal-appearing colonic mucosa; however, biopsy demonstrates a mononuclear infiltrate within the lamina propria, and a subepithelial collagen band may be present. Risk factors include concurrent autoimmune conditions, cigarette smoking, and certain medications (eg, nonsteroidal anti-inflammatory drugs).