Ultrasonic assessment of hydronephrosis of pregnancy.

Real-time renal ultrasonographic scans were obtained of 204 subjects, comprising 159 pregnant and 45 control subjects. A classification of hydronephrosis based on calyceal diameters was established, and the overall incidence of hydronephrosis was found to be 90% on the right side and 67% on the left side. Calyceal diameters for both kidneys were found to increase gradually throughout pregnancy, the right more rapidly than the left. Neither parity nor a history of urinary tract problems was found to be relevant to the degree of dilatation.