S3857 Clean Sweep: Unexpected Symptom Resolution of Microscopic Colitis Following Colonoscopy

Introduction: Microscopic colitis (MC) is a chronic inflammatory condition of the colon characterized by progressive, non-bloody diarrhea. While endoscopy findings may be normal, inflammatory changes can be seen in microscopy. Although treatment with antidiarrheals and budesonide is often effective, symptom recurrence and variable treatment responses remain clinical challenges. We highlight 2 cases of biopsy-proven MC in which patients demonstrated complete symptom resolution after colonoscopy. These cases illustrate a potential therapeutic effect of mechanical gut cleansing and the modulatory role of the microbiome in symptom control. Case Description/Methods: A 77-year-old woman with cerebrovascular accident on ASA, OSA, gastroesophageal reflux disease, hypertension who presented for colonoscopy for persistent watery diarrhea refractory to loperamide, with an unremarkable infectious workup. Pathology from colonic biopsies revealed collagenous colitis. She was prescribed budesonide but never filled the prescription and had complete resolution of symptoms following her colonoscopy without recurrence. The second case is a 62-year-old man with CAD on ASA, hypertension, hyperlipidemia, who presented with persistent chronic watery diarrhea, initially thought to be due to post-COVID complications. The mucosa appeared normal during colonoscopy, with pathology showing lymphocytic colitis. He then reported resolution of symptoms following colonoscopy. Two years later, his symptoms returned; a repeat colonoscopy re-demonstrated diffuse lymphocytic colitis. Following colonoscopy, the patient reported complete resolution of symptoms, with improved stool frequency and consistency. Discussion: These cases suggest a potential association between mechanical bowel preparation and symptom resolution in MC. There is some literature describing this phenomenon - 1 prospective study by Batista et al. in 2022 found 53% of MC patients experienced clinical remission following colonoscopy.1 These observations may be explained by temporary alterations in the composition and diversity of the microbiome after bowel cleansing, thus raising questions regarding the role of microbial modulation in symptom management. Further investigation into the role of the gut microbiome is warranted in the context of therapeutic targets in MC.