This occurs when liver function is markedly impaired. It can be acute or chronic and may be the outcome of a wide variety of disorders,eg,
- Acute viral hepatitis.
- Extensive necrosis due to poisoning eg some drug overdoses,hepatotoxic chemicals,adverse drug reactions.
- Cirrhosis of the liver.
Liver failure has serious effects on other parts of the body.
HEPATIC ENCEPHALOPATHY.
The cells affected are the astrocytes in the brain. The condition is characterised by apathy,disorientation,muscular ridgity and confusion,progressing to coma. Several factors are involved,eg :
- Nitrogenous bacterial metabolites absorbed from the colon,which are normally detoxified in the liver,reach the brain via the blood.
- Other metabolites,normally present in trace amounts,eg ammonia,may reach toxic concentrations and change the permeability of the cerebral blood vessels and the effectiveness of the blood-brain barrier.
- Hypoxia and electrolyte imbalance.
BLOOD COAGULATION DEFECTS.
The liver fails to synthesise substances needed for blood clotting.
OLIGURIA AND RENAL FAILURE.
Portal hypertension may cause the development of oesophageal varices. If these rupture,bleeding may lead to fall in blood pressure sufficient to reduce the renal blood flow,causing progressive oliguria and renal failure.
OEDEMA AND ASCITES.
These may be caused by the combination of two factors:
- Portal hypertension raises the capillary hydrostatic pressure in the organs drained by the tributaries of the portal vein.
- Diminished production of serum albumin and clotting factors reduces plasma osmotic pressure.
Together these changes cause the movement of excess fluid into the interstitial spaces where it causes oedema. Eventually free fluid accumulates in the peritoneal cavity and the resultant ascites may be severe.
JAUDICE.
The following factors may cause jaudice as liver failure develops:
- Inability of the hepatocytes to conjugate and excrete bilirubin.
- Obstruction to the movement of bile through the bile channels by fibrosis tissue that has distorted the structural framework the liver lobules.
