Liver Encephalopathy

Substances absorbed into the bloodstream from the intestines pass through the liver, where toxins are normally removed. Many of these toxins are normal breakdown products of the digestion of protein. In liver encephalopathy, toxins are not removed because liver function is impaired. Also, some toxins may bypass the liver altogether through connections formed between the portal venous system (which supplies blood to the liver) and the general (systemic) venous system as a result of liver disease. A surgical bypass (portal-systemic shunt) to correct portal hypertension may have the same effect. Whatever the cause, the outcome is the same: Toxins can pass to the brain and affect its function. Exactly which substances are toxic to the brain is not known; however, high levels of protein breakdown products in the blood, such as ammonia, appear to play a role.

In a person with long-standing (chronic) liver disease, encephalopathy is usually triggered by an event such as an acute infection or an alcoholic binge, which increases liver damage. Or encephalopathy may be triggered by eating too much protein, which increases the levels of protein breakdown products in the blood. Bleeding in the digestive tract, such as from dilated, twisted veins in the esophagus (esophageal varices), can also lead to a buildup of protein breakdown products, which may directly affect the brain. Certain drugsespecially some sedatives, analgesics, and diureticsmay also trigger encephalopathy. When such a precipitating cause is removed, the encephalopathy may disappear.

Symptoms and Diagnosis

The symptoms of liver encephalopathy are those of decreased brain function, especially impaired consciousness. In the earliest stages, subtle changes appear in logical thinking, personality, and behavior. The person's mood may change, and judgment may be impaired. Normal sleep patterns may be disturbed. The person's breath may have a musty sweet odor. When the person stretches out the arms, the hands cannot be held steady and the person displays a crude flapping motion of the hands (asterixis). As the disorder progresses, the person usually becomes drowsy and confused, and movements and speech become sluggish. Disorientation is common. A person with encephalopathy may be agitated and excited, but this is uncommon. Seizures are also uncommon. Eventually, the person may lose consciousness and lapse into a coma.

An electroencephalogram (EEG) (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Electroencephalography) may help in diagnosing early encephalopathy. Even in mild cases, an EEG shows abnormal brain waves. Blood tests usually show abnormally high levels of ammonia.

In an older person, liver encephalopathy may be more difficult to recognize in its early stages, because its initial symptoms (such as disturbed sleep patterns and mild confusion) may be attributed to dementia or are erroneously labeled as delirium.

Treatment

A doctor looks for and tries to remove any precipitating cause of the deterioration in brain function, such as an infection or a drug that the person is taking. A doctor also tries to eliminate toxic substances from the intestines, usually by restricting the person's diet. Protein is reduced or eliminated from the diet, and oral or intravenous carbohydrates serve as the main source of calories. Later, a doctor may increase the amount of vegetable protein (such as soy protein) rather than animal protein, thereby improving the protein balance without worsening the encephalopathy. The higher fiber content of a vegetable diet tends to speed up the passage of food through the intestines and alter the acidity in the intestines, thereby helping reduce absorption of ammonia. A synthetic sugar (lactulose) , taken by mouth, has similar beneficial effects: It alters the acidity of the intestines, and it acts as a laxative, which tends to speed up the passage of food through the intestines, helping to decrease the absorption of ammonia. Cleansing enemas also may be given. Occasionally, a person may take neomycin, an antibiotic. Neomycin reduces the quantity of intestinal bacteria that normally help digest protein; however, prolonged use of neomycin can impair kidney function and cause deafness.

With treatment, liver encephalopathy is frequently reversible. In fact, complete recovery is possible, especially if the encephalopathy was precipitated by a reversible cause. However, for a person in a severe coma as a result of acute liver inflammation, the disorder is fatal up to 80% of the time despite intensive treatment.