Fate of residual stones after percutaneous nephrolithotomy: a critical analysis.

PURPOSE

To analyze the fate of residual stones after percutaneous nephrolithotomy (PCNL) and identify the factors that predict spontaneous passage.

PATIENTS AND METHODS

We retrospectively analyzed the records of 2469 patients who underwent PCNL at our center between January 2000 to January 2008.

RESULTS

Residual fragments (RF) were identified in 187 (7.57%) patients. The most common site of RF was lower calix (57.7%), and the mean size of RF was 38.6 +/- 52 mm(2). Eighty-four stones passed spontaneously at a mean follow-up of 24 months (range 1-100 mos). Of the stones that passed spontaneously, 65.47% did so in 3 months. RF <25 mm(2) and those situated in the renal pelvis had the best chance of clearance. Stepwise multiple regression analysis showed that a history of intervention (P < 0.006), metabolic abnormalities such as hypercalcuria (P < 0.001) and hyperuraecemia (P < 0.03), preoperative nephrostomy drainage (P < 0.05), presence of a Double-J stent, (P < 0.001), time of presentation of residue (P < 0.08), size of residue (P < 0.007), and surgeon experience (P < 0.001) were significant factors in predicting the fate of RF after PCNL.

CONCLUSIONS

The most common site of post-PCNL RF was the lower calix. Renal pelvic RF <25 mm(2) have the best chance of spontaneous passage. Approximately half the RF will pass spontaneously, and the majority will clear in 3 months. The size of the residual stone, history of intervention, renal failure, and metabolic hyperactivity are predictors of persistence of RF.