P2277 - Hyperammonemic Encephalopathy Secondary to Sigmoid Conduit Urinary Diversion

Kevin Groudan, MD, David Desilets, MD
University of Massachusetts Medical School - Baystate, Springfield, MA

Introduction: Sigmoid conduit urinary diversion, also referred to as a ureterosigmoidostomy, was first performed in 1851 for a patient with bladder extrophy. Hyperammonemic encephalopathy as a result of sigmoid conduit urinary diversion is very rare, with only a few cases reported in the literature. We report a patient status post ureterosigmoidostomy who presented with altered mental status and was found to have elevated ammonia levels, consistent with hyperammonemic encephalopathy.

Case Description/Methods: A 72-year-old man with chronic hyperammonemia status post ureterosigmoidostomy as a child for congenital malformation of the bladder and ureters presented by ambulance for altered mental status. He was found down at home naked and extremely confused by his ex-wife. He was intubated on arrival for a Glasgow Coma Scale score of 3. Initial labs were significant for an ammonia level of 543 mg/L from a baseline of around 60 mg/L. Liver function tests were normal, including an INR of 1.1, AST and ALT of 17 u/L and 18 u/L, total bilirubin of 0.3 mg/dL and alkaline phosphate of 55 IU/L. Head imaging was unremarkable. His presentation was suspected to be due to his acute on chronic hyperammonemia. The reason for increased ammonia production at this time was unclear.

The patient was managed with lactulose 30 g every two hours and rifaximin 550 mg twice daily for three days however his ammonia levels remained elevated in the 400 mg/L range. On hospital day 4, he was taken for hemodialysis with normalization of his ammonia levels to the 30 mg/L to 40 mg/L range. Urology recommended maximizing medical therapy to minimize ammonia reabsorption, and if unsuccessful, considering conversion to an ileal conduit. The patient was extubated on hospital day 11. After a prolonged hospital stay spanning 35 days, his mental status returned to baseline.

Discussion: The mechanism of hyperammonemia in the setting of sigmoid conduit urinary diversion is exposure of the colon to urine. Bacterial colonizers of the colon such as Proteus mirabilis cause fermentation of uric acid into ammonia, which is subsequently absorbed into the blood stream. Reduced metabolic capacity of the liver from cirrhosis or portacaval shunts increases the risk of pathological levels of ammonia in the post-hepatic circulation. Our patient did not have concomitant liver disease. In conclusion, hyperammonemic encephalopathy is a rare complication of ureterosigmoidostomy that should be considered in the differential diagnosis of altered mental status.


Disclosures:


Kevin Groudan, MD, David Desilets, MD. P2277 - Hyperammonemic Encephalopathy Secondary to Sigmoid Conduit Urinary Diversion, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.