[Dilatation of the upper urinary tract in pregnancy--incidence, severity and follow-up. A sonographic study].

Incidence, onset and degree of the dilatation of upper urinary tract as well as the course throughout pregnancy was sonographically assessed in 310 pregnant women without symptoms from the urinary tract. 30 patients were regularly observed from the 16th week of gestation until delivery and within one week post partum. A grading system based on maximum calyceal diameter was used. 25% showed dilated calyces, primiparae more often than multiparae. The right kidney was dilated in 56, the left in 3 and both kidneys in 20 women. No decrease in parenchymal diameter was found during longer lasting dilatation of the pelvicalyceal system. Within one week after delivery the dilatation disappeared in nearly all cases. A gradual linear increase in incidence and severity of dilatation throughout pregnancy was found.