Second-look nephroscopy: Big stones justify costs

January 1, 2009

Second-look flexible nephroscopy after percutaneous nephrolithotomy is cost-effective only for patients who have larger residual stone fragments.

Dallas-Second-look flexible nephroscopy after percutaneous nephrolithotomy (PCNL) is cost-effective only for patients who have larger residual stone fragments, according to findings from a study by researchers at University of Texas Southwestern Medical Center, reported at the 2008 AUA annual meeting.

The procedure demonstrated cost-effectiveness only when patients had residual stone fragments larger than 4 mm, said Jay D. Raman, MD, a urology fellow at UT Southwestern under the direction of senior investigator Yair Lotan, MD, associate professor of urology. Thirty-six percent of patients who had smaller stone fragments eventually became symptomatic, and almost 50% of these symptomatic fragments required surgical intervention. In contrast, 67% of patients with stone fragments larger than 4 mm became symptomatic, and all those who became symptomatic required surgical intervention.

At Dr. Raman's institution, the cost of each second-look nephroscopy exceeded the estimated average cost of care for patients with a residual stone fragment by about 40%.

However, he added, the cost analysis model used in the study did not account for the potential benefit of reduced anxiety about future unexpected stone pain afforded by second-look flexible nephroscopy.

PCNL is effective for management of large or complex renal calculi. Although the procedure's goal is a stone-free kidney, a proportion of patients will have residual fragments after an initial PCNL procedure.

"Second-look flexible nephroscopy is not routinely performed to retrieve small, residual fragments because fragments are considered 'clinically insignificant' and because second-look flexible nephroscopy is not viewed as cost effective," said Dr. Raman.

UT Southwestern urologists have questioned whether small, residual stone fragments really are clinically significant. As a result, second-look flexible nephroscopy has become the standard practice.

A second look at "second-look"

To continue the exploration of the role and cost-effectiveness of second-look nephroscopy, Dr. Raman and colleagues reviewed published studies involving 645 patients, of whom 40% had clinically insignificant residual fragments that became symptomatic. In 57% of the cases, the patients subsequently required surgical intervention.

The cost-effectiveness of second-look flexible nephroscopy after PCNL was examined by reviewing the natural history of residual fragments after PCNL at UT Southwestern and creating a cost model based on meta-analysis of published outcomes for clinically insignificant residual stone fragments.

Dr. Raman and colleagues identified 527 patients who underwent PCNL between 1999 and 2007 and who had had at least 6 months' radiographic follow-up. Of those patients, 42 were observed to have residual fragments.

The endpoint of the study was a symptomatic residual-fragment event requiring medical or surgical therapy.

The meta-analysis of published literature yielded an average cost of $1,743 for each patient who had a clinically insignificant fragment. That average cost included lost wages and the costs of the emergency room visit and the surgical intervention. In contrast, second-look nephroscopy cost $2,475 at Dr. Raman's institution.

In the UT Southwestern series, 33 of 42 patients had residual stone fragments of 4 mm or less. During a median follow-up of 41 months, 12 (36%) became symptomatic and five of these (42%) required surgical intervention.

Of the nine patients with larger residual fragments, six (67%) became symptomatic and all six (100%) required surgical intervention.

Dr. Raman said alterations in two assumptions would change the cost-benefit analysis: the likelihood of a symptomatic event and the likelihood that a symptomatic event will require surgical intervention.

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