Hematuria as a Diagnostic Clue to Non-cirrhotic Hyperammonemia Due to Corynebacterium urealyticum Urinary Tract Infection: A Case Report

Hyperammonemia is an important cause of altered mental status in older adults; however, non-cirrhotic hyperammonemia in the absence of underlying liver dysfunction is easily overlooked. Hyperammonemia secondary to urinary tract infection (UTI) caused by urease-producing bacteria is relatively rare, and reliable clinical clues for early diagnosis have not been fully established. We report the case of a 95-year-old woman with Alzheimer's disease residing in a nursing facility. She had macroscopic hematuria for two days without any change in consciousness. On the day of admission, she was found unresponsive at breakfast and was transported to the emergency department with impaired consciousness. On arrival, she had renal dysfunction and marked hyperammonemia (168 µg/dL) but normal liver function tests. Her urine was alkaline, turbid, and purulent with gross hematuria, and her mental status improved rapidly after bladder catheterization and fluid resuscitation. Urine culture yielded <i>Corynebacterium urealyticum</i>, and she was diagnosed with non-cirrhotic hyperammonemia secondary to a UTI caused by this urease-producing organism. Including the present case, a review of 33 English- and Japanese-language reports identified gross hematuria in 15 cases, microscopic hematuria alone in 11, and no hematuria in seven; thus, 78.8% of patients demonstrated some degree of hematuria. These findings suggest that, in older patients with preserved liver function who present with impaired consciousness, the presence of hematuria is an important clue to hyperammonemia secondary to a UTI due to urease-producing bacteria. When hematuria is observed, clinicians should consider this entity in the differential diagnosis and promptly assess urine pH, urinary retention, and indwelling urinary catheters to identify ammonia-producing sources and perform timely drainage to prevent delays in diagnosis and treatment.