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liver disease

Is liver disease in cystic fibrosis a biliary or thrombotic disorder?
Thank you for this interesting question.

Liver disease indeed occurs in CF patients. In the mildest and most frequent form there are only liver test abnormalities of the blood sample, with no symptoms and no burden for the patients (10-35% of the patients). The worst and most rare form of CF liver disease slowly evolves into cirrhosis (liver scarring) (in 5-15% of patients).

Liver disease can be classified as biliary liver disease (the main problem is in the bile ducts) or thrombotic liver disease (the main problem is in the blood vessels).

The current theory about the origin of liver disease in CF is complex, and many questions are still unanswered. In patients with CF, there is a reduced function of the CFTR protein, a chloride channel. CFTR is expressed in the bile ducts and assures the transport of water and chloride into the bile. That way, it makes the bile more fluid. When the CFTR chloride channel is not working, the bile is not fluid enough, and only slowly flows to the gall bladder. This can lead to liver damage and liver scarring. The liver disease in CF is thus in part a biliary disorder.

But when we look at the symptoms of liver disease in patients with CF, it is not clear that the bile ducts play the most important role. With biliary liver disease there are often complaints of itching and jaundice (yellowing of the skin and eyes). These symptoms are rare in CF liver disease which behaves more as a thrombotic condition with early onset of 'portal hypertension'. A scarred liver can then lead to varicose veins in the esophagus, with a risk of severe esophageal bleeding. This risk of bleeding can be reduced by medication (beta-blockers), by removing or injecting the varicose veins during a gastroscopy or by the diversion of the hepatic circulation (the so called porto-systemic shunt). In case of portal hypertension the spleen is often enlarged. This implies a decrease in platelets (the spleen breaks them down).

Additionally, recent research at the University of Leuven has shown that if we study the livers of patients with CF under the microscope, we often see damaged blood vessels in the liver. Those are often clogged or they even disappeared. This may explain the portal hypertension. However it is still unclear why the blood vessels in the liver are affected and why some CF patients have liver damage where as others do not, although they have the same defect in the chloride transport. Improved understanding could lead to better treatment.

At present CF liver disease can only partially be treated: with a water-soluble bile acid (ursodeoxycholic acid) that makes the bile more fluid, and most likely retards the evolution to severe liver disease. Further treatment of the liver disease consists of optimizing the nutritional status, detecting and treating the complications. Luckily the need for liver transplant is rare.

Dr. P. Witters