Fetor hepaticus is a distinctive musty, sweet odor of the breath that typically indicates hepatic encephalopathy, a serious and potentially life-threatening complication of severe liver disease. The odor arises from the liver’s inability to metabolize and detoxify volatile sulfur-containing compounds (mercaptans) produced by bacterial degradation of methionine. These compounds accumulate in the blood and are exhaled via the lungs, producing the characteristic breath odor.

Pathophysiology

1. Mercaptan Accumulation: Damaged hepatocytes fail to metabolize sulfur-containing compounds from gut bacteria.

2. Systemic Circulation: Mercaptans enter the bloodstream due to impaired detoxification.

3. Pulmonary Excretion: These volatile compounds are exhaled via the lungs, producing characteristic breath odor.

4. Neurologic Impact: Ammonia accumulation leads to astrocyte swelling, cerebral edema, and neurologic dysfunction, manifesting as hepatic encephalopathy.

Emergency Interventions

Detection of fetor hepaticus signals potential hepatic decompensation. Immediate steps include:

1. Assess Level of Consciousness (LOC): If the patient is comatose, evaluate airway, breathing, and circulation.

2. Airway Management: Prepare for intubation and mechanical ventilation if respiratory compromise is present.

3. IV Access & Monitoring: Establish peripheral IV lines for fluid and electrolyte replacement; begin continuous cardiac monitoring.

4. Urine Output: Insert an indwelling catheter to monitor renal function.

5. Laboratory Workup: Obtain arterial and venous blood samples for blood gases, ammonia levels, electrolytes, liver function tests, coagulation profile, and complete blood count.

6. Supportive Care: Position patient supine with the head of the bed elevated ≥30°, administer supplemental oxygen, and provide hemodynamic support as needed.

History and Physical Examination

History

• Obtain a thorough history from the patient or family, focusing on:

  • Onset and duration of hepatic disease

  • Precipitating factors such as infection, surgery, blood transfusion, sedative or analgesic overuse, alcohol intake, excessive protein intake, or GI bleeding

  • Symptoms of hepatic encephalopathy: confusion, altered sleep patterns, tremors, agitation

Physical Examination

• Neurologic: Assess for asterixis, tremors, hyperreflexia, Babinski sign, and level of consciousness.

• Cardiopulmonary: Monitor for tachycardia, hypotension, tachypnea, and signs of shock.

• GI & Hepatic: Evaluate for jaundice, hepatomegaly, ascites, and abdominal tenderness.

• Other Findings: Look for GI bleeding (hematemesis, melena) and skin changes (cool, pale, or moist skin).

Medical Causes

Special Considerations

• Treatment: Focused on reducing systemic ammonia levels and addressing precipitating causes.

  • Lactulose: Non-absorbable disaccharide to acidify colon and trap ammonia.

  • Neomycin or Rifaximin: Reduce ammonia-producing gut bacteria.

  • Sorbitol: Osmotic diarrhea to eliminate nitrogenous waste.

  • Low-Protein Diet: Temporarily reduce protein intake while maintaining nutritional needs.

  • Advanced Measures: Hemodialysis or plasma exchange for refractory cases.

• Monitoring: Closely track LOC, vital signs, intake and output, fluid balance, and electrolyte status.

Patient Counseling

• Educate on disease progression, dietary modifications, and the importance of adherence to prescribed medications.

• Instruct caregivers to recognize early signs of encephalopathy, including confusion, lethargy, tremors, and changes in behavior.

• Discuss the need for regular follow-up and monitoring of liver function.

Pediatric Considerations

• Children approaching hepatic coma may present with irritability, distraction, or refusal to cooperate rather than classical signs.

• Early recognition is critical to prevent rapid deterioration.

Geriatric Considerations

• Elderly patients may show subtle cognitive disturbances (confusion, forgetfulness) in addition to fetor hepaticus.

• Coexisting comorbidities can complicate management and mask symptoms.

Conclusion

Fetor hepaticus is a hallmark sign of advanced hepatic encephalopathy and indicates urgent evaluation and management of liver failure. Healthcare professionals must recognize this symptom promptly, assess neurologic and hemodynamic status, identify precipitating factors, and implement interventions to reduce ammonia and support vital organ function.

References

1. Devictor, D., Tissieres, P., Afanetti, M., & Debray, D. (2011). Acute liver failure in children. Clinical Research Hepatology and Gastroenterology, 35, 430–437.

2. Shanmugam, N. P., Bansal, S., Greenough, A., Verma, A., & Dhawan, A. (2011). Neonatal liver failure: Aetiologies and management. European Journal of Pediatrics, 170, 573–581.

3. Ferenci, P. (2017). Hepatic encephalopathy. New England Journal of Medicine, 377, 2554–2561.

4. Vilstrup, H., Amodio, P., Bajaj, J., et al. (2014). Hepatic encephalopathy in chronic liver disease: 2014 Practice Guideline by the American Association for the Study of Liver Diseases and European Association for the Study of the Liver. Hepatology, 60(2), 715–735.