Unilateral absence of ureteral jets in the third trimester of pregnancy: pitfall in color Doppler US diagnosis of urinary obstruction.

Among 23 asymptomatic pregnant women with ureteral jets noted at color Doppler ultrasonography, jets were detected at only one ureteral orifice in three (13%) during the third trimester. In each such case, normal jets were detected from the suspicious ureter after the patient turned to the contralateral decubitus position. A unilaterally absent jet noted in the third trimester of pregnancy should not be interpreted as a sign of ureteral obstruction unless the finding persists in the contralateral decubitus position.