Schistosomiasis

The urinary system is the primary target of Schistosoma haematobium infection, which leads to granuloma formation in the lower urinary tract that heals with fibrosis and calcification. While the early lesions may be associated with distressing acute or subacute symptoms, it is the late lesions that constitute the main clinical impact of schistosomiasis. The latter include chronic cystitis, ureteric fibrosis, ureterovesical obstruction or reflux which may lead to chronic pyelonephritis. Secondary bacterial infection and bladder cancer are the main secondary sequelae of urinary schistosomiasis.The kidneys are also a secondary target of S. mansoni infection, attributed to the systemic immune response to the parasite. Specific immune complexes are responsible for early, often asymptomatic, possibly reversible, mesangioproliferative lesions which are categorized as ‘class I’. Subsequent classes (II–VI) display different histopathology, more serious clinical disease, and confounding pathogenic factors. Class II lesions are encountered in patients with concomitant salmonellosis; they are typically exudative and associated with acute-onset nephrotic syndrome. Classes III (mesangiocapillary glomerulonephritis) and IV (focal segmental sclerosis) are progressive forms of glomerular disease associated with significant hepatic pathology. They are usually associated with immunoglobulin A deposits which seem to have a significant pathogenic role. Class V (amyloidosis) occurs with long-standing active infection with either S. haematobium or S. mansoni. Class VI is seen in patients with concomitant HCV infection, where the pathology is a mix of schistosomal and cryoglobulinaemic lesions, as well as amyloidosis which seems to be accelerated by the confounded pathogenesis.Early schistosomal lesions, particularly those of the lower urinary tract, respond to antiparasitic treatment. Late urological lesions may need surgery or endoscopic interventions. As a rule, glomerular lesions do not respond to treatment with the exception of class II where dual antiparasitic and antibiotic therapy is usually curative. Patients with end-stage kidney disease may constitute specific, yet not insurmountable technical and logistic problems in dialysis or transplantation. Recurrence after transplantation is rare.