What are the diagnostic criteria for hepatic encephalopathy?

Diagnosing Hepatic Encephalopathy

The diagnosis of hepatic encephalopathy (HE) is primarily made through clinical assessment and exclusion of other causes of brain dysfunction, with neuropsychometric testing for covert forms and careful evaluation of precipitating factors. 1

Clinical Assessment and Grading

Overt Hepatic Encephalopathy (OHE)

• Diagnosed using clinical criteria and graded according to:
  • West Haven Criteria (WHC) for severity assessment 1
  • Glasgow Coma Scale (GCS) for more severe cases 1
• Severity classification:
  • Grade I: Mild confusion, altered mood, impaired attention
  • Grade II: Lethargy, disorientation, inappropriate behavior
  • Grade III: Somnolence, confusion, responsive to stimuli
  • Grade IV: Coma, unresponsive to stimuli 1

Covert Hepatic Encephalopathy (CHE)

• Includes Minimal Hepatic Encephalopathy (MHE) and Grade I HE 1
• Not obvious on routine clinical examination
• Requires specialized testing for diagnosis 1

Diagnostic Testing

Neuropsychometric Testing

• For covert HE (MHE and Grade I), use validated testing strategies:
  • Paper-pencil tests: Psychometric Hepatic Encephalopathy Score (PHES) 1
  • Computerized tests: Critical Flicker Frequency (CFF), Inhibitory Control Test (ICT), Scan Test, or Stroop Test 1
  • Animal Naming Test: Simple screening tool where patient lists animal names for 1 minute
    • Cut-off of <20 animal names suggests covert HE 1

Laboratory Testing

• Blood ammonia levels:
  • Not diagnostic on their own but useful for exclusion 1
  • A normal ammonia level in a patient with suspected OHE calls for diagnostic reevaluation 1
  • Proper collection technique is critical:
    • Fasting patient
    • Avoid venous stasis
    • EDTA-containing tube placed immediately on ice
    • Transport to lab at 4°C within 60-90 minutes 1

Brain Imaging

• Not specific for HE diagnosis but important for differential diagnosis 1
• Recommended for first-time HE episodes to exclude other pathologies 1
• CT or MRI should be performed when:
  • First presentation of HE
  • Atypical presentation
  • Suspected intracranial hemorrhage (5-fold increased risk in this population) 1

Diagnostic Algorithm

1. Clinical assessment:

   • Evaluate for signs of altered mental status in a patient with known liver disease
   • Grade severity using West Haven Criteria

2. Rule out differential diagnoses:

   • Perform blood tests: CBC, comprehensive metabolic panel, toxicology screen
   • Consider brain imaging (CT/MRI) to exclude structural causes 1, 2

3. Evaluate for precipitating factors:

   • Gastrointestinal bleeding: Endoscopy, CBC, rectal exam
   • Infection: CBC, cultures
   • Constipation: Abdominal X-ray
   • Electrolyte disturbances: Serum electrolytes
   • Medication effects: Review medication history 2

4. For suspected covert HE:

   • Perform validated psychometric or neurophysiological tests
   • Consider testing in patients with impaired quality of life or concerns about employment/driving safety 1

Common Pitfalls and Caveats

• Relying solely on ammonia levels: While elevated in most HE cases, ammonia levels alone cannot diagnose HE. However, normal levels should prompt reconsideration of the diagnosis 1

• Missing precipitating factors: Always search for and address underlying triggers such as GI bleeding, infection, electrolyte disturbances, constipation, or medication effects 2

• Overlooking covert HE: This condition significantly impacts quality of life and daily functioning but requires specialized testing for diagnosis 1

• Improper ammonia measurement: Failure to follow proper collection and processing protocols can lead to falsely elevated levels 1

• Neglecting differential diagnoses: HE is a diagnosis of exclusion; always rule out other causes of altered mental status, especially in first presentations 1

By following this structured approach to diagnosis, clinicians can effectively identify and grade hepatic encephalopathy, leading to appropriate treatment decisions and improved patient outcomes.