Recurrent hyperammonemic encephalopathy involving urease-producing and nonurease-producing bacteria

While hyperammonemic encephalopathy (HAE) is commonly associated with hepatic dysfunction or urease-producing bacterial infections, its occurrence in the absence of urease-producing bacteria is rarely reported. An 85-year-old woman with neurogenic bladder developed two episodes of HAE. In the first episode, Morganella morganii, a urease-producing bacterium, was identified as the causative pathogen. Despite successful treatment, the patient developed a second episode of HAE caused by nonurease-producing Escherichia coli. No significant hepatic dysfunction or other metabolic disorders were identified, and both episodes resolved with appropriate antibiotic therapy and urinary catheterization. This case highlights the potential for HAE to develop even when urease-producing bacteria are not detected in culture tests, particularly in patients with underlying urinary dysfunction such as neurogenic bladder.