Prevalence of Microscopic Colitis in Chronic Diarrhea Patients Attending Al-Azhar University Hospital in New Damietta

Background: Microscopic colitis (MC) is an underdiagnosed cause of chronic diarrhea that characterized histologically as lymphocytic colitis (LC) or collagenous colitis (CC). The condition can manifest with watery, non-bloody diarrhea, and is frequently misdiagnosed, owing to the lack of endoscopic findings. The purpose of this study is to evaluate the frequency of MC in patients presented with chronic diarrhea attending Al-Azhar University Hospital in New Damietta.Methods: A cross-sectional study was carried out in the Department of Hepato-gastroenterology and Infectious Diseases, Al-Azhar University Hospital, New Damietta, from December 2023 to December 2024. A total of 262 adult patients (≥18 years old) diagnosed with chronic diarrhea (≥4 weeks) were enrolled. We excluded patients with infectious colitis or inflammatory bowel disease or systemic diseases affecting diarrhea, drug-induced diarrhea and major comorbidities. All subjects were assessed through detailed clinical examination, laboratory tests and colonoscopy with thorough biopsy sampling of the various colonic segments. Microscopic subtypes of colitis were identified by histopathological examination.Results: Among the 262 patients, 22 (8.4%) were diagnosed with microscopic colitis. Lymphocytic colitis was found in 12 patients (4.6%), while collagenous colitis was identified in 10 patients (3.8%). Endoscopic findings were unremarkable in 59.5% of cases, highlighting the importance of biopsy in diagnosing MC. MC patients had a significantly longer duration of diarrhea (4.5 ± 1.5 months vs. 1.8 ± 0.9 months; p<0.001), higher prevalence of nocturnal diarrhea (p=0.005), weight loss (p=0.012), and bloating (p=0.020). Proton pump inhibitor (PPI) use was significantly higher in MC patients compared to non-MC patients (63.6% vs. 39.6%, p=0.02).Conclusion: Microscopic colitis was proven in 8.4% of all patients with chronic diarrhea, where lymphocytic colitis appeared a little bit more often than collagenous colitis. The case highlights the importance of performing colonic biopsies in patients with chronic diarrhea and normal endoscopy.