Cirrhosis or fibrosis describes the condition where part of an organ is scarred, thereby impairing its function. It's most common in the liver and kidneys, but can occur in any organ of the body. It usually occurs when an environmental toxin severely overtaxes the ability of an organ to process the toxin. By far the most common form of cirrhosis is cirrhosis of the liver caused by alcohol abuse as the liver is responsible for metabolizing alcohol.