What are lab abnormalities characteristic of encephalopathy in cirrhosis?

Updated: Oct 15, 2020
  • Author: David C Wolf, MD, FACP, FACG, AGAF, FAASLD; Chief Editor: BS Anand, MD  more...
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An elevated arterial or free venous serum ammonia level is the classic laboratory abnormality reported in patients with hepatic encephalopathy. This finding may aid in the assignment of a correct diagnosis to a patient with cirrhosis who presents with altered mental status.

However, serial ammonia measurements are inferior to clinical assessment in gauging improvement or deterioration in patients under therapy for hepatic encephalopathy. No utility exists for checking the ammonia level in a patient with cirrhosis who does not have hepatic encephalopathy.

Some patients with hepatic encephalopathy have the classic, but nonspecific, electroencephalogram (EEG) changes of high-amplitude low-frequency waves and triphasic waves. Electroencephalography may be helpful in the initial workup of a patient with cirrhosis and altered mental status, when ruling out seizure activity may be necessary.

CT scan and MRI studies of the brain may be important in ruling out intracranial lesions when the diagnosis of hepatic encephalopathy is in question.

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