USMLE – Chronic Liver Disease and Renal Failure
Chronic liver disease and chronic liver failure are not synonymous terms, although the former can eventually lead to the latter. Chronic liver disease causes many clinical features, such as are seen in cirrhosis, and chronic liver failure develops when liver function can no longer maintain normal physiological conditions. The term ‘hepatic decompensation’ is often used when chronic liver failure occurs and may be precipitated by a number of events including infection or variceal hemorrhage. Chronic liver failure is a syndrome characterized by clinical and laboratory features including ascites and edema due to sodium retention by the kidneys, the normal function of which is dependent on liver function; hepatic encephalopathy due to brain dysfunction consequent on liver failure; jaundice due to inadequate hepatic bilirubin transport; and hypoalbuminemia and coagulation abnormality due to deficient hepatic protein synthesis.
Renal failure consequent on liver failure can occur in cirrhosis. The kidneys themselves are intrinsically normal and renal failure is thought to result from altered systemic blood flow including diminished renal blood flow. The condition is called’ functional renal failure of cirrhosis’ or the ‘hepatorenal syndrome’. It occurs in advanced cirrhosis, almost always with ascites and uremia is characterized by the absence of proteinuria or abnormal urinary sediment, a urine sodium excretion below 10 mmol/day, and a urine/plasma osmolality ratio greater than 1.5. It is important to exclude hypovolemia by measuring the central venous pressure and giving colloidal solutions such as human albumin solutions to maintain the pressure at 0-5 cm of water. The treatment of hepatorenal syndrome includes giving dopamine (1-2 ug/kg/min) to maximize renal blood flow and thereafter diuretics. Uremia and endogenous protein breakdown should be limited by restricting protein intake to 20 g/day and giving 300 g of carbohydrate daily. Recovery depends ultimately on improvement of liver function but in chronic liver disease this seldom occurs. Accordingly, the prognosis is very poor unless liver transplantation can be undertaken.