Second-look nephroscopy for residual fragments: Size matters

May 18, 2008

Second-look flexible nephroscopy after percutaneous nephrolithotomy (PCNL) is cost effective only for residual stone fragments larger than 4 mm, according to findings from a study reported at the AUA meeting yesterday.

Second-look flexible nephroscopy after percutaneous nephrolithotomy (PCNL) is cost effective only for residual stone fragments larger than 4 mm, according to findings from a study reported at the AUA meeting yesterday.

Second-look nephroscopy costs about 40% more than following patients with clinically insignificant residual fragments and intervening only if the fragments become symptomatic. However, observation also has potential costs that should be factored into clinical decision making.

"Observing stones less than or equal to 4 mm avoids 60% of second-look procedures, but results in morbidity or the need for intervention in 40% of patients with residual stones," said Jay D. Raman, MD, who worked on the study with Yair Lotan, MD, and colleagues at the University of Texas Southwestern Medical Center in Dallas.

Second-look flexible nephroscopy is not used routinely to retrieve stone fragments after PCNL because the fragments are considered clinically insignificant and second-look nephroscopy is perceived as not cost effective.

Dr. Raman and colleagues question whether residual stone fragments really are clinically insignificant. As a result, second-look nephroscopy is standard care at their institution.

A review of published studies involving 527 patients showed that about 40% of patients with clinically insignificant residual fragments after PCNL are symptomatic and 57% of those patients subsequently require surgical intervention.

On the basis of the published studies, investigators determined that the cost of observing patients with clinically insignificant fragments averaged $1,743, including lost wages and surgical intervention. In contrast, second-look nephroscopy cost $2,475 at UT Southwestern.

A two-way sensitivity analysis revealed a subset of patients for whom second-look nephroscopy would be cost effective. In patients with residual fragments >4 mm, the cost of a symptomatic clinical event and surgical intervention would exceed that of nephroscopy. In different clinical scenarios, the cost of care would range from $2,552 to $6,172.