Schistosomiasis: Clinical Management of Liver Disease

Abstract

Schistosoma infection is one of the most important causes of noncirrhotic portal hypertension in Latin America, Africa, and Asia.1 Schistosomiasis is a waterborne disease caused by a blood fluke of the genus Schistosoma. Schistosoma man soni and S. japonicum are the species most commonly involved in liver disease. Schistosoma intercalatum, S. mekongi, and, occasionally, S. haematobium may also induce liver disease.2 Despite some species-specific variations in inflammatory/fibrotic responses, Schistosoma-induced liver injury results from a granulomatous inflammatory reaction around trapped Schistosoma eggs in the presinusoidal peri portal spaces. In early phases of infection, a predominantly hypercellular nonfibrotic granuloma response produces liver dysfunction that is not clinically detectable. Imaging studies may reveal enlargement of the left liver lobe without changes in the liver parenchyma or splenomegaly. Revers ibility of these findings is expected in 12 months following chemotherapy.3 Development of chronicity results in colla gen deposition in the periportal spaces, which is the basis of the pathognomonic pathological feature of schistosomal associated liver fibrosis known as ‘‘Symmers’ pipestem fibro sis’’. In addition, fibrosis is accompanied by angiogenesis. Vascular disturbances include severe reduction and distor tion of the portal venous system and hyperplasia and hyper trophy of the arterial system.4 The occlusion of the portal veins is associated with portal hypertension marked by splenomegaly, portocaval shunting, and gastrointestinal vari ces. Ultrasonography (US) may reveal periportal fibrosis around periportal spaces, liver parenchymal heterogeneity, splenomegaly, enhanced portal vein dimensions, and the presence of collateral vessels. Despite successful parasite elimination, the effect of chemotherapy on the inflammatory response within the liver is negligible. As the fibrosis pro gresses, with or without active infection, repeated episodes of variceal bleeding may be accompanied by hepatic deteri oration that can lead to a fatal outcome. Worsening of liver function might also be provoked by Schistosoma-associated coinfections or other comorbidities. Viral hepatitis, malaria, HIV infection, mixed Schistosoma species, alcoholism, or nonalcoholic steatohepatitis each may enhance tissue dam age and/or inflammatory/fibrotic responses, thus promoting disease progression.