Hyperammonemia
Background
Pathophysiology
- Acquired: liver failure results in shunting of blood from the liver to the inferior vena cava, decreased filtration of blood and removal of nitrogen-containing toxins by the liver, and then hyperammonemia.
- Congenital: Defect in one of the enzymes of the urea cycle, which leads to lower production of urea from ammonia.
Types
- Primary
- Caused by several inborn errors of metabolism
- Characterized by reduced activity of urea cycle enzymes
- Secondary
- Caused by inborn errors of intermediary metabolism (i.e. reduced activity of enzymes that are not part of the urea cycle)
- Normally from acute or chronic liver failure
- Caused by inborn errors of intermediary metabolism (i.e. reduced activity of enzymes that are not part of the urea cycle)
Clinical Features
Differential Diagnosis
Evaluation
Acquired vs. Congenital
- Acquired
- Diseases that result in liver failure
- Medications (e.g. valproic acid overdose)
- Severe dehydration (from small intestinal bacterial overgrowth)
- Glycine toxicity (CNS symptoms and nausea)
- Congenital
- Genetic
Management
- Treat underlying disorder
Disposition
- Depends on cause
External Links
References
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