Modified patient position for percutaneous nephrolithotomy shows advantages

December 1, 2011

Placing a patient in a "prone-flexed" position offers a number of benefits for percutaneous nephrolithotomy.

Key Points

Toronto-Surgeons cannot do much to alter human anatomy, but they can make organs such as the kidney more accessible by altering a patient's posture on the operating table, suggests a recent study from St. Michael's Hospital, University of Toronto.

The study's results indicate that placing a patient in a "prone-flexed" position offers a number of benefits for percutaneous nephrolithotomy. The position, according to first author Joshua D. Wiesenthal, MD, and colleagues:

"Compared to the prone position, the prone-flexed position actually elevates the kidney closer to the skin and shortens the distance. That can be important in heavy and obese patients, where using a longer instrument can be avoided," Dr. Wiesenthal told Urology Times.

This study of the benefits of the prone-flexed position for nephrolithotomy is one of a series of studies from the researchers. Dr. Honey developed this approach for PNL. For this proof-of-concept study, the authors obtained abdominal-pelvic triphasic computed tomography reconstructions on 16 patients placed in both the standard prone and in the prone-flexed position.

The research team found that in the prone-flexed position, the left kidney was displaced lower than the right in 92% of the cases. Such a displacement would have lowered an upper pole puncture from above the eleventh rib to one above the twelfth rib in nearly half (45%) of the cases.

Compared to the prone position, the right kidney in the prone-flexed position was closer to the skin surface by a mean of 8.4 mm and the left by a mean of 13.4 mm. Previously published studies have shown the altered patient posture leads to excellent success rates with minimal operative morbidity. It is well tolerated by patients.

"I think this allows us to use standard-length instruments in a vast majority of cases, and the patients are probably helped as a result," co-author Kenneth T. Pace, MD, MSc, told Urology Times.

Dr. Wiesenthal said that these and previous studies were conducted on a segmented operating table that could be adjusted to create a prone-flexed platform. He said institutions lacking such tables can place patients in a prone-flexed position by utilizing 30° or 45° bolsters.

"The take home is that this is a simple modification that facilitates percutaneous access without requiring a change in technique," Dr. Wiesenthal said.