INTRODUCTION: Angiotensin converting enzyme inhibitors (ACEI) are one of the most commonly prescribed anti-hypertensives. Angioedema, one of its known adverse effects, occur between 0.1% to 0.7% mostly affecting the lips, tongue, face and upper airways. Isolated small bowel angioedema due to ACEI is rare. We present a case of a middle-aged female with abdominal pain and imaging findings of ileitis which resolved after discontinuation of lisinopril. CASE DESCRIPTION/METHODS: A 48-year-old female with hypertension and organ limited granulomatosis with polyangiitis presents with a 1-year history of right lower quadrant abdominal pain and not associated with fever, weight loss, and diarrhea. Patient denies NSAIDs use but has been on lisinopril for 6 years. Upper endoscopy and colonoscopy were unremarkable. CT abdomen with contrast revealed focal segmental inflammation of the proximal ileum. Additional evaluations were negative including infectious etiologies, inflammatory bowel disease, ANCA, anti-transglutaminase antibodies, and c1-esterase inhibitor. Repeat CT abdomen 1 month after discontinuation of lisinopril showed interval complete resolution of the segmental ileal inflammation, and patient reports improvement of her abdominal pain. DISCUSSION: Angioedema of the small intestine is a rare adverse effect of ACEI which is one of the top causes of drug-induced angioedema. It is thought to be due to elevated bradykinin level resulting in vasodilation and increase vascular permeability resulting in edema. Patients may present with diarrhea, nausea, vomiting, abdominal pain and rarely, as acute abdomen requiring laparotomy. Symptoms usually occur 72 hours after starting ACEI but can develop weeks or years after and resolve 48 hours after stopping the medication. Laboratory tests are often unremarkable and radiologic studies reveal segmental thickening of the small intestinal wall, ascites and mesenteric edema which may mimic inflammatory bowel disease, mesenteric ischemia, or vasculitis. Treatment involves discontinuation of the offending drug. Given that patient has been on lisinopril for 6 years and the unremarkable laboratory tests results, it is very important to have a high index of suspicion for drug induced small intestine angioedema aside from ruling out other possible etiologies. Clinicians must review each patient’s medication list and their side effects since small intestine angioedema is rare and under recognized. Early diagnosis help prevent unnecessary investigations and surgical interventions.