MON-003 A Rare Cause of Chronic Diarrhea

Abstract Disclosure: M. Obeidat: None. R. Chamseddin: None. K. Alnimer: None. D. Obeidat: None. M. Asfaw: None. W. Taha: None. Introduction: Neuroendocrine tumors (NETs), are uncommon tumors that arise from specific neurohormonal cells. They are primarily found in the lungs, small intestine, and pancreas. The incidence of neuroendocrine tumors has been rising in recent decades, likely due to the increased frequency of screening and diagnostic endoscopic studies. Here we report a case of a duodenal neuroendocrine tumor diagnosed in a patient with chronic diarrhea. Case Description: A 70-year-old African American female with a past medical history of type II diabetes mellitus was evaluated outpatient for 6 months of diarrhea. She reported spontaneous onset of daily diarrhea, with episodes of nocturnal diarrhea, unrelated to food intake, and associated with weight loss. She denied heat intolerance or palpitations. The diarrhea was unresponsive to loperamide. The physical exam was unremarkable. Had a negative screen for celiac disease, hyperthyroidism, inflammatory bowel disease, and infectious causes. However, her pancreatic elastase enzyme level was decreased, indicating pancreatic insufficiency. Upper endoscopy and colonoscopy were done, which identified two large polypoid lesions, each measuring 1 to 1.5 cm in the duodenal bulb. A hot snare polypectomy was done, and biopsies were also taken from the colon, gastric mucosa, and duodenal mucosa. Microscopic findings showed a grade 1 well-differentiated neuroendocrine tumor with a Ki-67 index of <2%. Tumor cells stained positive for synaptophysin, chromogranin A, and cytokeratin. Serum chromogranin A levels were elevated. CT scan of the chest, abdomen, and pelvis showed no evidence of metastasis. PET/CT revealed two foci of radiotracer uptake within the proximal duodenum, suspicious for neuroendocrine tumors. After discussing the risks and benefits of surgery, the patient consented to undergo Whipple procedure. After the surgery, diarrhea resolved, and she recovered well. Conclusion: Chronic diarrhea has a broad differential diagnosis, and a workup can usually identify its cause in more than 90% of cases. Diarrhea caused by neuroendocrine tumors is primarily related to hormonal secretion. However, even nonfunctional NET can present with diarrhea by causing intestinal irritation and inducing pancreatic insufficiency. Although rare, neuroendocrine tumors should be included in the differential diagnosis when evaluating patients with chronic recurrent diarrhea. Presentation: Monday, July 14, 2025