Effectiveness of noncontrast computed tomography in evaluation of residual stones after percutaneous nephrolithotomy

We prospectively compared the sensitivity of antegrade pyelography (AGP), plain film radiography (KUB film), and noncontrast thin-slice abdominal CT for detecting residual stones after percutaneous nephrolithotomy (PCNL).

We prospectively evaluated 50 patients (53 renal units) who underwent PCNL for radiopaque renal pelvic stones with noncontrast abdominal CT 1 month postoperatively. We compared the number and size of residual fragments, as determined by immediate postoperative AGP and 1-month KUB film and CT scan.

Stone-free rates according to AGP, KUB film, and noncontrast CT were 73.6% (39/53), 62.3% (33/53), and 20.8% (11/53), respectively. However, if clinically insignificant residual fragments are included in the success rates, these rates increased to 84.9% (45/53), 83.0% (44/53), and 41.5% (22/53), respectively. Of the 22 patients in whom residual stones were detected by CT but not by KUB film, 10 (45.5%) had stones >4 mm in diameter on CT, with a mean size of 7.4 mm. The sensitivity for the detection of residual fragments was 47.6% for KUB films as judged by noncontrast CT. After CT, seven patients received extracorporeal shockwave lithotripsy for residual stones.

Noncontrast thin-slice abdominal CT was the most accurate imaging method to determine the stone-free rate after PCNL. Noncontrast abdominal CT gives accurate information for selecting patients who may benefit from additional treatment and for planning follow-up.