A hepatologist can treat a wide range of liver diseases and complications, depending on their severity, cause, and type. These include viral hepatitis, an infection of the liver caused by viruses such as hepatitis A, B, C, D, or E; alcoholic liver disease, a condition caused by excessive alcohol consumption; non-alcoholic fatty liver disease (NAFLD), which is caused by the accumulation of fat in the liver; autoimmune liver diseases, a group of conditions caused by the immune system attacking the liver or bile ducts; genetic liver diseases, a group of conditions caused by inherited mutations or defects in genes that affect the liver function; liver cancer, a malignant tumor that originates from the liver cells or bile ducts; and liver failure, a life-threatening condition that occurs when the liver is unable to perform its essential functions. Each of these can cause inflammation, scarring, cirrhosis of the liver, increased risk of liver cancer or failure, abnormal accumulation or metabolism of substances in the liver, jaundice, abdominal pain, weight loss, ascites, confusion, coma, bleeding or edema. Treatment depends on the severity and type of condition and can include surgery, chemotherapy, radiotherapy, targeted therapy, supportive care and medications. In some cases a liver transplant may be necessary.