Ultrasonography for diagnosis of obstructing ureteral calculus.

The reliability of ultrasonography in diagnosing ureteral obstruction caused by calculus was prospectively investigated. In 60 consecutive cases sonograms were compared with excretory urograms. The sonographic diagnosis was correct in 27 (79%) of the 34 cases shown by urography to have ureteral obstruction, and the sonograms showed the causal calculus in 17. The rate of false negative sonographic diagnosis was thus 21%. In two patients with no urographic abnormality, the sonograms indicated ureteral calculus without signs of obstruction. Ultrasonography may be used as an alternative to emergency urography for initial imaging in cases of suspected ureteral obstruction, but urography remains the standard method for evaluating the obstructed urinary tract, due to its greater accuracy and ability to assess renal function.