An Unusual Gastrointestinal Cause of Hypokalemia

Abstract

Question: A 60-year-old male man came to emergency with history of painless protracted watery diarrhea for past 4 weeks associated with generalized weakness and swelling of both feet. He denied passing mucus or blood per rectum. His past medical history was insignificant. He denied consumption of laxatives or over-the-counter drugs for constipation. He seemed to be dehydrated and had tachycardia, pallor, and pedal edema. His stool microscopy revealed no leukocytes, ova, blood, or red blood cells. Renal function revealed a normal creatinine with a potassium of 2.81 mEq/L. His serum albumin was 3.1 g. Urine examination revealed no proteinuria and echocardiography revealed good ejection fraction with normal sized chambers. Serum potassium failed to correct despite supplementation and remained below the normal range. Transtubular potassium gradient was 1.7, suggestive of extrarenal losses. His tissue transglutaminase serology was negative and gastroduodenoscopy revealed normal duodenal folds. Duodenal biopsy was also inconclusive. A contrast-enhanced computed tomography scan of the abdomen revealed an enhancing mucosal lesion in the sigmoid colon (Figure A).Colonoscopy revealed a large pedunculated polyp in the sigmoid colon (Figure B [white light] and Figure C [narrow band imaging]) and a small pedunculated polyp in ascending colon (Figure D [narrow band imaging]). Hot