Hyperammonemic Encephalopahty Can Result from a Duodenal Switch

Abstract

A 41-year-old female had inadequate weight loss 2 years after a vertical sleeve gastrectomy. 1 year prior to presentation, she underwent revision to a duodenal switch with formation of a duodeno-ileal anastomosis. At presentation she had evidence for protein-calorie malnutrition. She denied alcohol use; total parenteral nutrition (TPN) was initiated. Upper endoscopy revealed a normal esophagus and post-operative changes of sleeve gastrectomy with duodenal switch; a nasoileal tube was placed to begin enteral nutrition. On day 9, the patient was moved to the intensive care unit after onset of catatonia and unresponsiveness. On exam, she had no signs of chronic liver disease. Her INR was 1.4, platelet count 237 and had minimal elevations of serum ALT and AST. She had no evidence for metabolic acidosis (AGAP-8 and lactic acid-1.1). CT scan of the head was unremarkable. There was no deficiency of vitamin B12, folate, copper, or zinc, but she had hyperammonemia with a blood level of 223 mcg/dl. The differential diagnosis for non-hepatic hyperammonemia includes medications, hyperalimentation, infections with urease producing bacteria, surgical-induced nutritional deficiency, and errors of metabolism. Other potential explanations were excluded for this patient. She was started on a protein restriction of 40 grams/day, lactulose enemas and high dose intravenous thiamine. She had a decrease in her serum ammonia levels with improvement in her mental status. A 24-hour urine collection revealed an elevated orotic acid level (2.9 mmol/mol Cr) supporting Ornithine Transcarbamylase Deficiency. She underwent revision of her ileo-ileostomy, and the common channel was increased in length. On day 30, TPN was discontinued. She was discharged on a protein limited diet and oral lactulose. This exceedingly rare phenomenon with similar presentations has been described previously involving predominantly female patients developing an often fatal hyperammonemic encephalopathy after gastric bypass surgery, which in some patients was up to 28 years post-operatively. The exact mechanism remains unclear, but this disorder is believed to involve unmasking of inborn errors of urea metabolism after bariatic surgery, the most common of which is Ornithine Transcarbamylase Deficiency. This case report demonstrates that this disorder can also occur after duodenal switch. Gastroenterologists need to be aware of this disorder due to the number of patients undergoing bariatric surgery.