CHARLOTTETOWN, Canada—Second-look nephroscopy improves the stone-free rate in patients with renal calculi undergoing single-tract percutaneous nephrolithotomy (PCNL), according to a study presented at the Canadian Urological Association’s 2010 annual meeting.

Researchers reviewed the outcomes of 285 PCNL procedures performed between January 2000 and December 2008. They found a 52% stone-free rate after the initial procedure and a 76% stone-free rate after second-look nephroscopy.

In addition, the investigators determined that stone diameter and a stone’s location in the upper pole of the kidney predicted whether there are residual stones after second-look nephroscopy. Stones larger than 4 cm were 30% less likely to be cleared compared with smaller stones; stones in the upper pole were 3.3 times less likely to be cleared than stones in the lower pole or renal pelvis.

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“This is the first time researchers have tried to create a model to predict outcome of PCNL,” noted Dr. Khaled Shahrour, MD, an endourology fellow at the University of Pittsburgh School of Medicine. “This is important because it can help the surgeon to decide if the patient with a stone will benefit from this procedure or not.”

He added it was surprising to discover that stones in the upper pole are less likely to be removed. Dr. Shahrour and his colleagues now try to approach upper-pole stones using upper-pole access or via ureteroscopy.

Dr. Shahrour’s team found that 37% of patients had stones in the upper pole. The median stone diameter was 3.56 cm and 64% of the patients had more than one stone.

Forty-eight percent of patients had residual stones after initial PCNL. Sixty-nine percent of these patients underwent second-look nephroscopy. Twenty-four percent of those who underwent the second-look procedure still had residual stones.

A total of 57 patients underwent ancillary treatments for residual stones, including ureteroscopy, shock wave lithotripsy, or repeat PCNL. In the end, only 7% of patients still had some residual stones.