Acute on chronic liver failure and prognostic factors: time for reevaluation.

ical care units has significantly rised in recent years because of an increase —however insufficient— in the number of those units (1). Nevertheless, the concept of liver failure has become somewhat blurry due to the various definitions in use. Acute liver failure is currently defined as a sudden, serious impairment of liver function in the form of coagulopathy and encephalopathy in patients with no previous liver disease (2,3). Chronic liver failure develops only in patients with cirrhosis and is characterized by a progressive deterioration of the different liver functions in an irreversible, usually slow manner, often associated with increased portal pressure and related complications. The recently coined term acute on chronic liver failure (ACLF) refers to a sudden impairment of liver function in a patient with previous chronic liver disease, by definition potentially reversible with therapy and always with a trigger factor, even though the latter may not always be identified (4). In ACLF the patient may occasionally survive on conventional therapy, but most often than not will need multiple organ support including mechanical ventilation, inotropic support or kidney replacement therapy, among others. The study by Freire et al. included in this issue of the journal examines a high number of the latter two types of liver failure (5) in subjects admitted on several grounds in a gastroenterology intensive care unit. Another study by these same authors assessed the usefulness of these prognostic models in patients with all sorts of serious digestive conditions (6). The primary differences between chronic liver failure and ACLF include the fact that the former is progressive, results from the natural history of cirrhosis, and —while manageable with drug or instrumental therapy— is irreversible by definition until the patient either dies or undergoes a liver transplant. The latter, however, may be a chronic liver condition with or without cirrhosis, with an acute deterioration of liver function as a result of a noxa unrelated to the natural history of the liver disorder, and most often considered reversible no matter the severity of functional impairment (4). ACLF remains a little known condition mainly because of its highly variable definitions as used in different studies. These are patients with well compensated chronic liver disease in which liver function is decompensated by an acute factor such as sepsis, gastrointestinal bleeding, ischemia, or added liver damage including viral hepatitis, alcohol, or toxics (6). The most relevant characteristic is reversibility when the trigger factor is managed before it is too late. Factors that may impair liver function in patients with prior chronic liver disease are categorized in two major groups: hepatotoxic factors and systemic factors. The former group refers to alcohol ingestion, exposure to drugs or hepatotoxic substances, and infection with hepatotropic viruses. The latter group, which includes Acute on chronic liver failure and prognostic factors: time for reevaluation 61130-0108/2011/103/4/169-176 REVISTA ESPAÑOLA DE ENFERMEDADES DIGESTIVAS Copyright © 2011 ARÁN EDICIONES, S. L. REV ESP ENFERM DIG (Madrid) Vol. 103, N. ° 4, pp. 169-176, 2011