Sonographic screening for urinary tract abnormalities in patients with Schistosoma haematobium infection: pitfalls in examining pregnant women.

In areas where Schistosoma haematobium is endemic, urinary schistosomiasis and pregnancy are frequently concomitant; however, both these conditions may produce similar urinary tract changes in ultrasound scans and hence their differential diagnosis may be difficult. In patients with urinary schistosomiasis, focal and/or diffuse urinary bladder wall changes are frequently detected ultrasonically. Dilatation of one or both ureters and progressive hydronephrosis may be observed in more severe cases. Satisfactory ultrasound examination of the urinary bladders of pregnant women is generally not feasible because mechanical compression by the fetus or transitory lower urinary tract infection hampers adequate filling of the bladder. Pregnancy itself is frequently associated with dilatation of one or both ureters and/or hydronephrosis; this is due to hormonal factors, infection, or compression of one or both ureters by the enlarged uterus and growing fetus. Hence, when sonography of the urinary bladder is not feasible such pregnancy-associated changes are virtually indistinguishable from those caused by S. haematobium, and may be incorrectly attributed to the latter. Pregnant women, therefore, should be excluded from ultrasonic surveys of urinary schistosomiasis. In contrast, ultrasound scans of adolescents and of women with positive parasitological findings and/or pathological alterations in the urinary tract should include examination of the uterus in order to assess whether the woman is pregnant; thereby, misinterpretation of sonographic findings can be avoided. Pregnant women with significant hydronephrosis must be closely followed up by an obstetrician since this condition may indicate a complication of the pregnancy; in some cases only a postpartum examination will permit definitive diagnosis.