HEPATIC VENOOCCLUSIVE DISEASE AFTER BONE-MARROW TRANSPLANT

Hepatic veno-occlusive disease (VOD) is a non-thrombotic obliteration of the lumina of small intrahepatic veins. VOD has been reported after exposure to a wide variety of pathogens. It has been suggested that the chemoradiotherapy used as the conditioning regimen for bone marrow transplant (BMT) is now the main cause of this disease. However, the pathogenesis of VOD after BMT is probably multifactorial. Endothelial injury of sinusoids and small hepatic veins is considered to be the initial event in genesis of VOD. This injury is followed by deposition of fibrin-related aggregates in the subendothelial zone. These aggregates, and the intramural entrapment of fluid and cellular debris, occlude progressively the hepatic venous outflow and generate a postsinusoidal intrahepatic hypertension. Clinically, VOD is characterized by jaundice, weight gain, ascites, painful hepatomegaly and platelet refractoriness developing early post transplant, although other postransplant liver disturbances can produce a similar syndrome. VOD diagnosis is usually established by applying the clinical criteria proposed by the Seattle and Baltimore groups. When clinical diagnosis of VOD is uncertain, a transjugular liver study including a transvenous biopsy and measurement of the gradient between wedged and free hepatic venous pressure, is recommended in order to establish an accurate diagnosis. According to the literature data, the incidence of VOD ranges from 0 to 70% and its mortality from 20 to 50%. This very wide range is attributable to the different incidence of risk factors in the different series and to the differences in applying the diagnostic criteria. Pretransplant liver disease, conditioning regimen intensity and composition, and use of other hepatotoxic drugs are proven risk factors for VOD. Other factors, such as the type of transplant or patient age, have been suspected but not definitively confirmed. There are no specific measures for VOD prophylaxis and treatment, but some prospective randomized studies are in progress in order to evaluate promising approaches.