Schistosomiasis of the liver.

Schistosomiasis is an infection of trematodes, Schistosoma, causing periportal fibrosis and liver cirrhosis due to deposition of eggs in the small portal venules. In schistosomiasis caused by S. mansoni, sonography shows echogenic thickening or fibrotic band along the portal veins. CT shows low-attenuation bands or rings around the large portal vein branches in the central part of the liver with marked enhancement. Hepatoplenomegaly, liver cirrhosis, portal hypertension and gastroesophageal varies are commonly associated. In schistosomiasis caused by S. japonicum, sonography shows echogenic septae in the liver, utlining the polygonal liver lobules, mimicking "fish-scale" network appearance, reflecting fibrosis. CT shows periportal septae in the peripheral part of the liver parenchyma, producing "turtle-back" appearance, representing calcified eggs along the portal tracts. The portal tracts and hepatic capsule are enhanced on contrast-enhanced CT images. The size and shape of the liver are relatively preserved. MR images show fibrous septae as low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and these fibrous septae are enhanced. CT images of the lungs show multiple scattered nodules with halo of ground-glass opacities. Exudative granulomatous inflammation of the colonic wall may produce inflammatory polyps, fibrous thickening or stenosis of the colonic wall.