Clinically insignificant residual fragments: an acceptable term in the computed tomography era?

To assess the clinical relevance of small, asymptomatic, noninfection residual stone fragments (≤5 mm) after percutaneous nephrolithotomy (PNL), evaluated using spiral noncontrast-enhanced computed tomography (NCCT).

The present retrospective study included 75 patients who underwent PNL and were proved to have a single residual caliceal stone ≤5 mm as evaluated postoperatively by NCCT. All patients were free of urinary tract infections. The outcome of these residual fragments (RFs) were reassessed ≥12 months later using NCCT.

The mean follow-up period was 36.2 ± 20.1 months (range 12-96). Of the 75 evaluated patients, 25 (33.3%) passed the stones spontaneously during the follow-up period, 22 (29.35%) had stable asymptomatic RFs, 25 (33.3%) showed regrowth of the RFs, and 3 patients (4%) presented with slippage of the stones into the ureter. Asymptomatic patients with stable RFs elected to continue follow-up. For the remaining patients, 14 (18.7%) and 9 (12%) were referred to shock wave lithotripsy and PNL, respectively. The 3 patients with ureteral stones were treated with ureteroscopy. Only the RF size (>3 mm) correlated significantly with RF growth or ureteral obstruction (odds ratio 1.882, 95% confidence interval 0.919-3.854; P = .05).

Small RFs (≤5 mm) after PNL, as assessed by NCCT, should be expected to require active intervention in one third of the patients at intermediate follow-up. A small, single, RF (≤3 mm), as assessed by NCCT, can be considered clinically insignificant.