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Dear patient's son, developement of hepatic encephalopathy
in a patient of cirrhosis
of liver is called decompensation of cirrhosis and it can occur due to variety of reasons like infection e.g spontaneous bacterial peritonitis
etc; upper GI bleeding; diuretics leading to hypokalemia; renal failure; portocaval shunting; constipation
etc. What ever is the precipitating factor,all of these lead to accumulation of ammonia and other amines and chemicals in the blood that when enter the brain lead to encephalopathy. If these patients are properly treated in ICU along with the treatement of precipitating factors, a good majority of patients improve and come out of encephalopathy and others who don't improve land into coma and there is no test by which you can predict who are going to go into come and if the go in to coma then after how much of time will they go into come , although it generally happens over a period of few overs to few days.
Hope your father improves and wish him speedy recovery