Human schistosomiasis: A diagnostic imaging focused review of a neglected disease

Schistosomiasis is one of the major tropical and sub-tropical diseases caused by trematodal parasite of genus Schistosoma. This neglected disease affects 200 million people, resulting in the loss of 1.53 million disability-adjusted life years (DALY). The disease presents in wide spectrum including both acute and chronic forms, affecting multiple target organs. The schistosomal infection is mainly diagnosed by demonstrating evidence of infestation by parasitological, serological or molecular methods using samples such as stool, urine, blood or other body fluids and tissue specimens. However, these test methods have their own limitations in evaluating severity of morbidity. The role of diagnostic imaging modalities such as ultrasonography, CT scan and MR scan is crucial not only to diagnose the disease but also to evaluate the severity of the disease process and its complications in target organs. The clinical and imaging features of the disease can mimic other infectious as well as noninfectious disease. Thus, it is essential to be familiar for radiologists and physicians with the imaging features of schistosomiasis, so as to make accurate and timely diagnosis and thereby, reducing the morbidity and mortality of this disease. Ultrasound is considered as primary modality of choice as it is able to pick characteristic hepatosplenic and urinary lesions. Typical ultrasonographic findings of hepatosplenic schistosomiasis include periportal fibrosis, hypertrophy of the left liver lobe, atrophy of right liver lobe, splenomegaly, and ascites. CT and MR scan are valuable not only for hepatosplenic and urogenital schistosomiasis, but also for secondary and ectopic lesions such as those in CNS and lungs, which are difficult to be assessed by ultrasonography. Periportal fibrosis, map-like calcification of liver parenchyma, nodular enhancement of the cerebral mass are some typical imaging findings of schistosomiasis.