Diagnostic utility and clinical value of postpercutaneous nephrolithotomy nephrostogram

After percutaneous nephrolithotomy (PCNL), the current standard of care is to obtain a nephrostogram before removal of the nephrostomy tube to rule out distal ureteral obstruction. The aim of this study was to determine whether nephrostogram findings predict prolonged urinary drainage and postoperative ureteral stent insertion.

Data for all patients who had nephrostomy tubes inserted post-PCNL between January and December 2006 were retrospectively reviewed. Patients with radiolucent stones, concomitant procedures, or caliceal diverticula were excluded. All nephrostograms were reviewed to identify distal ureteral obstruction without evidence of residual fragments. The Fisher's exact test was used.

Fifty patients who underwent 51 PCNLs were included in the study (one patient had bilateral PCNLs). Nephrostograms were performed on median postoperative day (POD) 2 (range POD 2-8), and tubes were removed on median POD 2 (range POD 2-10). In 14 (27%) patients who had distal ureteral obstruction without ureteral stones, the nephrostomy tube was removed on the same day of nephrostography. Eight (16%) patients experienced a prolonged urinary leak (>24 hours). While obstruction on the nephrostogram predicted prolonged urinary leak (36% vs 8%; P = 0.02), none of these obstructed patients needed postoperative ureteral stent placement. A patient with a horseshoe kidney without distal ureteral obstruction had his nephrostomy removed on POD 2. He presented on POD 7 with prolonged urinary leakage and needed readmission with ureteral stent placement and Foley catheterization.

While distal obstruction seems to predict prolonged urinary leakage (more than 24 hours), it may not necessitate ureteral stent placement or prolonged nephrostomy drainage because blood clot or ureterovesical junction edema resolve spontaneously with expectant management.