A 52-year-old woman with cirrhosis (Child-Pugh Class C) is admitted with persistent hypoglycemia (42 mg/dL) and elevated blood lactate (6.8 mmol/L). Her ammonia is elevated at 180 µmol/L. Liver biopsy shows extensive fibrosis and hepatocellular necrosis. Which metabolic derangement best explains the concurrent hypoglycemia and elevated lactate in this patient?

Explanation

## Lactate Metabolism in Hepatic Failure **Key Point:** In advanced cirrhosis, the liver loses its capacity to perform gluconeogenesis from lactate, resulting in concurrent hypoglycemia and lactate accumulation (Type B lactic acidosis). This is a hallmark of hepatic decompensation. ### Pathophysiology of Lactate Accumulation in Cirrhosis **High-Yield:** The Cori cycle depends on intact hepatic gluconeogenic capacity. In cirrhosis: 1. **Reduced hepatic mass** — fibrosis and necrosis decrease functional hepatocytes 2. **Enzyme deficiency** — decreased expression of gluconeogenic enzymes (PEPCK, fructose-1,6-bisphosphatase, glucose-6-phosphatase) 3. **Impaired lactate uptake** — reduced hepatic blood flow and transporter function 4. **Substrate depletion** — loss of glycogen stores and reduced cofactor availability (NAD^+^, ATP) ### Metabolic Consequences ```mermaid flowchart TD A["Cirrhosis: Hepatic fibrosis & necrosis"]:::outcome B{"Hepatic gluconeogenic capacity?"}:::decision B -->|Severely reduced| C["Lactate accumulation<br/>(cannot be cleared)"]:::urgent B -->|Severely reduced| D["Hypoglycemia<br/>(no glucose production)"]:::urgent A --> B C --> E["Type B Lactic Acidosis<br/>(lactate >5 mmol/L, pH <7.35)"]:::urgent D --> F["Risk of seizures,<br/>altered mental status"]:::urgent E --> F ``` **Clinical Pearl:** Type B lactic acidosis (lactate >5 mmol/L with normal tissue oxygenation) in cirrhosis carries a mortality rate >80% and indicates acute hepatic decompensation or acute-on-chronic liver failure. ### Comparison: Lactate Metabolism in Health vs. Cirrhosis | Feature | Healthy Liver | Cirrhosis | |---------|---------------|----------| | **Lactate clearance** | 90% via gluconeogenesis | Severely impaired (<10%) | | **Glucose production** | 10–15 g/hour (fasting) | Minimal; hypoglycemia develops | | **Lactate threshold** | <2 mmol/L | Often >5 mmol/L | | **Cori cycle function** | Intact | Blocked | | **Prognosis with lactate >5** | Good with treatment | Poor; mortality >80% | **Mnemonic:** **HALT** = **H**epatic failure → **A**ccumulation of **L**actate → **T**ype B acidosis. ### Why Hypoglycemia Coexists Without hepatic gluconeogenesis, the liver cannot produce glucose from lactate, pyruvate, amino acids, or glycerol. Glycogen stores are depleted in advanced cirrhosis, leading to profound hypoglycemia. [cite:Harrison 21e Ch 370; Robbins 10e Ch 18]