Tubeless PNL: Studies address ideal stents, candidates

Cleveland-Two studies from the University of Minnesota and one from the University of Tennessee presented at the World Congress of Endourology tackled three important questions raised by the use of nephrostomy tubes: Which configuration best minimizes pain? How small can the tube be and remain effective? When can a nephrostomy tube be abandoned altogether?

"Patient discomfort is an important consideration for any surgical procedure, and of all the procedures performed for kidney stones, percutaneous nephrolithotomy is probably the most painful. We are searching for ways to reduce the pain," Manoj Monga, MD, professor of urologic surgery at the University of Minnesota, Minneapolis, told Urology Times.

Dr. Monga and colleagues compared the effect of two different nephrostomy catheter designs on postoperative pain in 18 patients, and concluded that shape makes a difference. Nine patients received the Flexima 8.3F pigtail nephrostomy tube (Boston Scientific, Natick, MA), and nine received the Percuflex 8.2F nephroureteral stent (Boston Scientific). The patients were blinded to the type of catheter being placed. The ease of placement was rated on a subjective scale of 1 to 4, with 1 being the most efficient. Patient pain was evaluated on a visual analog pain scale of 0 to 10, with 0 representing no pain. In addition, narcotic diaries were kept, with all pain medication being converted to morphine milliequivalents.

"The take-home message is that stent configuration is important and affects patient comfort," said Benjamin Canales, MD, a fellow in endourology in Dr. Monga's department and lead author of the study. "We are going to take a closer look at the type of pain these patients had. Although we have the analog scores, we did not differentiate whether the pain was localized to the bladder or flank. This would be the next step."

Dr. Canales also presented a retrospective study involving 99 patients undergoing percutaneous nephrolithotomy between 1998 and 2000 using a 6F antegrade nephroureteral catheter (Cook Urological, Spencer, IN). This is the smallest nephroureteral catheter to be used for this procedure, said Dr. Canales, who worked with chief clinical investigator E. James Seidmon, MD, professor of urology at the University of Minnesota.

With an average stone size of 2 cm, postoperative IV narcotic use was low (1.7 days), and the majority of stents (82%) were removed by postoperative day 2. In addition, average length of hospital stay was similar to that of other large PCNL series (2.5 days). Dr. Canales concluded that, due to its small size, the 6F catheter minimized postoperative narcotics and expedited both recovery and discharge.

Dr. Seidmon assisted in the development of the stent and holds a patent on it in conjunction with Cook Urological.

Best tubeless PNL candidates

Although tubeless percutaneous nephrostolithotomy has been around for more than 10 years, criteria for determining which patients are the best candidates are lacking. A third study was designed to address this problem.

"Our goal was to examine our experience with the tubeless procedure," said Keith Brightbill, MD, chief urology resident at the University of Tennessee Health Science Center, Memphis. "As we looked, we found that we had actually performed it in many patients with complex calculi, and the outcomes were excellent."

Dr. Brightbill, working with Robert W. Wake, MD, and colleagues, conducted a retrospective study that identified 43 patients with complex stones who had undergone tubeless PCNL during the last 6 years. The complex cases included 20 patients with total or partial staghorn stones, 11 with renal insufficiency, and 12 with infundibular stenosis/calyceal diverticulum. All patients had their nephrostomy tube removed in the operating room following the procedure. All had an internal ureteral stent placed perioperatively and a Foley catheter that remained overnight.