Sonographic visualization of the ureter in pregnancy.

We describe a method of differentiating physiological from pathological dilatation of the renal collecting system in pregnant patients. In physiological hydronephrosis the dilated ureter extends down only to the level of the common iliac artery. In 2 patients with distal ureteral stones a dilated ureter was visualized past the vessels. To determine the frequency and reliability of visualizing the ureters in pregnant patients 105 consecutive asymptomatic pregnant patients were examined. Hydronephrosis was found in 83 kidneys in 59 of the patients. The dilated ureter was visualized in 64 of the renal units. The anatomy was well demonstrated by color flow Doppler scanning and in all of these cases the dilated ureter was seen to taper where it crossed the common iliac artery. These results suggest that the presence of a dilated ureter past the iliac artery is strong evidence for pathological distal ureteral obstruction in pregnancy.