S4998 Eosinophilic Colitis Following Roux-en-Y Gastric Bypass: A Rare Case of Postoperative Eosinophilic Gastrointestinal Disease in an Atopic Adult

Introduction: Eosinophilic colitis (EC) is a rare inflammatory condition, with an estimated prevalence of less than 1–2 cases per 100,000 individuals, defined by dense eosinophilic infiltration of the colonic mucosa without secondary causes. It’s most often linked to food allergies, autoimmune conditions, medications, or parasitic infections. EC is particularly uncommon in adults and remains poorly described in the postoperative setting. We present a biopsy-confirmed case of EC developing shortly after Roux-en-Y gastric bypass, suggesting that gastrointestinal surgery may act as a physiological trigger for eosinophilic gastrointestinal disease in predisposed individuals. Case Description/Methods: A 30-year-old woman with morbid obesity and multiple allergies (latex, rubber, lidocaine, bee venom) underwent uncomplicated Roux-en-Y gastric bypass but developed abdominal pain, nausea, vomiting, and food intolerance within a week, leading to hospitalization for severe constipation; imaging showed fecal stasis and stercoral colitis, and sigmoidoscopy revealed mucosal erythema and ulcers, with biopsies showing mild active colitis without chronicity. She was discharged on Miralax® but was lost to follow-up, later returning with a 10-lb weight loss, nausea, and peripheral eosinophilia (26%); colonoscopy showed mild sigmoid erythema, and biopsies from the right, left, and sigmoid colon demonstrated marked eosinophilic infiltration of the lamina propria—124, 141, and 115 eosinophils per HPF, respectively. Diagnosed with EC, she was started on prednisone but couldn’t tolerate oral steroids due to nausea, requiring hospitalization and intravenous corticosteroids, which led to clinical improvement, resolution of eosinophilia, and normal follow-up colonoscopy. Discussion: Post-Roux-en-Y gastric bypass EC is rare but clinically important. Rather than a direct surgical complication, it may reflect immune dysregulation triggered by postoperative stress, altered antigen exposure, or microbiota shifts. Diagnosis is challenging due to patchy disease and nonspecific or absent endoscopic findings. Diagnostic criteria include GI symptoms, exclusion of secondary causes, and histologic eosinophil counts >100/HPF (right colon), >84/HPF (transverse), or >64/HPF (left). False negatives on initial biopsy are common, highlighting the need for repeat sampling. While most cases respond to corticosteroids, tumor necrosis factor-α inhibitors may help in refractory disease. This case highlights the importance of considering eosinophilic gastrointestinal disorders in post-bariatric patients with persistent gastrointestinal symptoms and eosinophilia.