Ultrasound in schistosomiasis mansoni

Abdel Wahab et al. (1979) were the first to report the ultrasound features of hepatosplenic schistosomiasis mansoni. Their findings were confirmed by several investigators in Africa (Fataar et al. 1984, Hussain et al. 1984) and in Brazil (Cerri et al. 1984, Domingues et al. 1993, Pinto-Silva et al. 1994, Lambertucci et al. 2001, 2008). Table I summarises the main findings reported by the above investigators. The first studies were carried out in hospitalized patients with severe hepatosplenic schistosomiasis; in most cases, there was also a history of upper digestive bleeding. In this scenario, ultrasound proved to be efficient in the diagnosis of liver fibrosis and in the differential diagnosis with other chronic liver diseases such as cirrhosis, steatosis and liver abscesses. In addition, ultrasound facilitated the exclusion of other diseases that evolved with splenomegaly, such as kalazar, lymphoma and portal vein thrombosis (Homeida et al. 1988). Liver fibrosis findings in ultrasound are similar to those described by pathologists in the autopsy theatre (Bogliolo 1957, Andrade & Bina 1983, Lambertucci et al. 2000). The schistosomal periportal fibrosis appears like an echogenic band surrounding the portal vessels from the hilum to the periphery of the liver; in advanced cases, the liver surface may develop pseudonodules as a result of fibrous tissue scaring and retraction. The gallbladder wall is thickened by echogenic tissue as shown in Fig. 1. Liver parenchymal echogenicity is usually preserved. The portal vein and its tributaries are generally dilated. Collateral veins with hepatofugal flow are frequently reported, especially in the following veins: left gastric, short gastric, splenorenal and parumbilical. In the parumbilical vein, the blood flows toward the umbilical scar, where it joins the superficial epigastric veins and may originate the “caput medusae”. With the intense use of ultrasound in everyday life, the authors noticed that other diseases shared some characteristics of the schistosomal hepatopathy. For example, other diseases presented some degree of periportal thickening in the hilum, like chronic portal thrombosis (cavernomatous transformation of the portal vein). Another difficulty comes from the coexistence of chronic hepatic viral infection or liver cirrhosis, which turn out to be difficult to differentiate from the hepatosplenic form of schistosomiasis. Table II lists the differential diagnoses of Symmers fibrosis and depicts some clues for differentiating them. Documented ultrasonographic regression of liver fibrosis was reported by Homeida et al. (1991) in 28 patients three years after treatment with praziquantel. Cota et al. (2006) studied 84 patients from a rural endemic area of Brazil four years after treatment with oxamniquine and confirmed the regression of fibrosis in 32% of the patients and the disappearance of splenomegaly in 48% of the patients. ultrasound showed moderate inter-observer reproducibility (kappa = 0.46) for patterns C through F of the Niamey-Belo Horizonte Protocol and a perfect intraobserver reproducibility (1.00) for static images. In addition, an agreement of 0.43-0.57 was observed for the dynamic study of the same patient in different moments; this was considered satisfactory compared to mammography readings using the Breast Imaging Reporting and Data System criteria of the American College of Radiology. For mammography, the agreement ranges from 0.25-0.75 (Santos et al. 2007).