Case Presentation:
A 64 year old male with a past medical history of congenital bladder exstrophy and ureterosigmoidostomy at 5 years of age with multiple subsequent revisions, recurrent urinary tract infections and a hospitalization for diverticulitis complicated by bowel obstruction a month prior presented to our emergency department after a motor vehicle accident due to sudden onset confusion. He had a similar episode two weeks prior which resulted in a hospitalization at an outside hospital. Workup for cerebrovascular accident at that time was negative and his mental status returned to baseline without intervention. On presentation, the vital signs were stable. He was oriented only to self, and was able to only follow simple commands. The remainder of the physical and neurological examination was normal. Laboratory studies including blood chemistry, complete blood count, liver function tests, serum toxicology, thyroid stimulating hormone, vitamin B12, Lyme serology, and coagulation panel were unremarkable, and a computed tomography scan of the head was normal. An ammonia level was checked which was markedly elevated at 208 µmol/L. Lactulose was started with only marginal improvement in mental status. Rifaximin was then initiated and the patient’s condition rapidly improved over the next few days and he was discharged home soon after at his baseline mental status.
Discussion:
While encephalopathy secondary to hyperammonemia is most commonly associated with hepatic dysfunction, it is quite rare in the setting of normal liver function. In our patient, his condition was likely due to ureterosigmoidostomy which has been identified as a cause of non‐hepatic hyperammonemic encephalopathy in multiple case reports. It is theorized that as urine enters the sigmoid colon, urease‐producing gut flora metabolize urea to ammonia which is subsequently reabsorbed into the systemic circulation. However, it remains unclear as to why hyperammonemic encephalophathy can manifest itself for the first time decades after surgery, and although several similar cases have been reported, a definitive etiology has never been identified. In our patient, his recent bowel obstruction may have been a causative factor. Considering that many species of gut flora have significant urease activity together with existing data suggesting that bowel obstruction can cause alterations in gastrointestinal flora to favor these urease‐producing bacteria, our patient’s recent bowel obstruction could have resulted in an increased ammonia load thereby leading to encephalopathy.
Conclusions:
Although hyperammonemic encephalopathy has previously been reported to occur in patients with ureterosigmoidostomy decades after surgery, a specific etiologic factor has never been identified. In this case, the patient’s recent bowel obstruction is strongly implicated as the precipitating factor of his hyperammonemia and subsequent encephalopathy. In turn, this focuses attention onto derangements in gastrointestinal flora as a cause of this rare condition.