Collagenous colitis: a rare cause of chronic diarrhea

Abstract

Listen

Translate article

Abstract Introduction: Collagenous colitis is a chronic inflammatory disease of the colon with a peak incidence in middle-aged adults. It is characterized by chronic diarrhea and pain from abdominal cramping, with near normal mucosa morphology under gross colonic examination by colonoscopy. Currently, the pathogenesis remains unclear but there is speculation of an association with abnormal collagen metabolism, contributing to prominent sub-epithelial matrix deposition. Patient concerns: A 51-year-old male patient without any underlying disease presented after experiencing watery light brown diarrhea 4–5 times per day for the past 2 months. Diagnosis: The diagnosis of collagenous colitis was confirmed by the pathological examination of the second colonic biopsy, which reported positive Masson's trichrome staining. Intervention: The patient was initially diagnosed with unspecified functional bowel disorder, but showed no clinical improvement after treatment with oral medication. Mesalamine therapy was administered after collagenous colitis was diagnosed by follow-up colonoscopy. Outcome: Normal bowel movement was restored in the patient after 2 weeks of mesalamine therapy. Conclusion: Collagenous colitis is a rare etiology of chronic diarrhea, which can only be diagnosed by pathology of colonic mucosa. Consequently, repeat colonoscopy with multiple stepwise random colonic biopsies at suspicious lesion sites or even normal-appearing mucosa should be considered in refractory chronic diarrhea patients without established diagnoses.