Hepatic Encephalopathy Without Hyperammonemia in the Setting of Liver Metastases by a Pancreatic Neuroendocrine Tumor.

Hepatic encephalopathy (HE) is a neurological impairment that typically occurs in patients with liver dysfunction or portosystemic shunting. Diagnosing HE can be challenging since it requires a process of exclusion. Ammonia is considered a major contributor to HE, though ruling out HE solely based on ammonia levels has the potential for misdiagnosis.  Malignancy infiltration is uncommon as an etiology of HE, although there are reported cases of HE patients with pancreatic neuroendocrine tumors (PNETs) diagnosed by the presence of hyperammonemia. We report a case of a disoriented patient with a PNET and diffuse metastases to the liver who presented without hyperammonemia. After excluding possible etiologies of altered mental status, we diagnosed the patient with HE and started on lactulose, which improved his condition. PNET patients can experience HE without hyperammonemia, and a thorough evaluation to rule out other etiologies is necessary for the diagnosis.