Minimally invasive percutaneous nephrolithotomy: A Chinese approach, "Beyond the Abstract," by Guohua Zeng and Wen Zhong

BERKELEY, CA (UroToday.com) - In our minimally invasive surgery center, we performed the first percutaneous nephrolithotomy (PCNL ) in China in 1984. Based on the belief that a small percutaneous tract would inflict less trauma to the renal parenchyma than standard PCNL, we modified the traditional technique of standard PCNL in an attempt to decrease the morbidity and complications.

The general procedure was more-or-less similar to other PCNL techniques, while some other differences, which were uniquely our own, are described as follows. After retrograde ureter catheterization with a 5-6Fr open-ended ureter catheter (Boston Scientific Corporation, Miami Technology Center, USA), all other procedures were performed in the prone position. Fluoroscopy-guided percutaneous punctures were made by the urologist, followed by puncture with an 18-gauge coaxial needle (Cook Incorporated, Bloomington, IN) into the designed calyx after the retrograde injection of contrast medium. A flexible 0.035 inch Zebra™ guide wire (Boston Scientific Corporation, Miami Technology Center, USA) was then inserted into the renal collecting system or down the ureter and through the needle sheath, under fluoroscopy guidance. The tract was dilated to 14Fr-18Fr by fascial dilators, stepwise, a matched peel-away sheath (Cook Incorporated, Bloomington IN) was then inserted. The renal stone was fragmented by pneumatic lithotriptor or Ho:YAG laser (or a combination), and removed by 8/9.8Fr rigid ureteroscope (Richard Wolf GmbH, German). The petty fragments could be flushed out by the forceful pulse flow, which was produced by Perfusion Pump (Jielun Medvice Ltd, Guangzhou, China). At the end of the procedure, a 5Fr Double-J stent and a 14Fr-18Fr silastic nephrostomy tube was fixed.

PCNL using a small tract for stone removal was first reported in 1997 by Helal and his colleagues where they used a 15F Hickman peel-away sheath as the working sheath with a 10F pediatric cystoscopy and forceps to remove 3 stones of 5-7mm in a 2-year-old child weighting 10kg. This technique was later reported frequently, and despite the use of various sheath sizes and instruments and the different terms for the procedure, all the authors believed that using a small tract had the potential advantage of decreased bleeding and trauma to the renal parenchyma. Since the smaller-size percutaneous tract would potentially require a longer time to dislodge stones than for standard PCNL, the indication for minimally invasive percutaneous nephrolithotomy (MPCNL), in their studies, was limited to those cases with a stone burden less than 2cm in diameter or pediatric upper urinary tract stones, or as a secondary tract for inaccessible or residual fragments to supplement standard PCNL.

Because of the lack of proper endoscopes and special equipment, they found it difficult to maintain good endoscopic view and even more difficult to remove the stone fragments via the smaller tract. During the practice of MPCNL, we generate a novel impulsive stream with high pressure, produced by MCC pump, to facilitate removing the fragment of calculi. This accelerated the operative course, and the other innovations of traditional PCNL technique, which altogether provided the assurance of high effectiveness of MPCNL in treating upper urinary tract stones. In this centre, MPCNL is routinely performed to treat upper tract stones of all sizes -- including staghorn, stones in the transplanted kidney, upper ureteric stones, and stones in solitary kidneys.

In this recently published paper, we reported our experience with MPCNL to treat upper urinary tract stones. Between 1992 and 2011, 12 482 patients who underwent 13 984 MPCNL procedures were entered into this study. Data on stone size, access number, operative time, hospital length-of-stay, stone-free rate (SFR), and complications according to the modified Clavien system were evaluated prospectively. The mean age of patients was 47.6 years (range 0.6–93). The mean stone size was 3.2 ± 0.8 (1.4–7.4) cm. The mean operative time was 83 ± 38 min. Mean hemoglobin drop was 13.5 ± 11.3 g/L. Mean hospital stay was 10.3 ± 6.4 days (2–22 days). The initial SFR after first procedure was 78.6 %. In 14.7 % of cases with a second look, the SFR increase to 89.9 %. At 3 months after auxiliary procedures (re-PCNL, ureterorenoscopy, and shock wave lithotripsy), the overall SFR was achieved to 94.8 %. A total of 3 624 complications (25.92 %) were observed in 2 591 (18.53 %) procedures. There were 2 355 grade I (16.84 %), 706 grade II (5.05 %), 553 grade III (3.95 %), 7 grade IV (0.05 %), and 3 death of grade V (0.02 %) complications. This large-scale contemporary analysis confirms MPCNL is still a safe and efficacious treatment option of kidney stones with a high stone-free rate and uncommon rate of high-grade complications.

Some urologists reported the lack of suitable equipment for MPCNL, but our practice had solved these problems by standardization of the use of equipment and simplification of the surgical technique. The Zebra guide wire as the only type of guide wire, a set of fascial dilators and peel-away sheath, semi-rigid WOLF ureteroscope, ballistic lithotripsy, and stone removal by irrigation supplemented by a rigid 5Fr forceps represents the optimal solution to all problems of MPCNL. These pieces of equipment are readily available in all units performing stone removal procedures. Most importantly, we had modified the fascial dilator by creating a mark on the lateral view to indicate how deep it had been stabled.

Even sonographically guided puncture has become more popular recently, the most preferred guidance being by X-ray fluoroscopy. The role of fluoroscopy is to confirm the puncture, monitor the passage of a guide wire, or to guide a puncture into a specific calyx in difficult cases, and also to detect possible residual stones. After the puncture has been performed with an 18-gauge needle, the use of a Zebra guide wire is preferred by our department because it is soft enough to passed down the ureter or coil up in a dilated calyx. The tract is dilated to 14-18Fr with fascial dilators on the guidance of fluoroscopy, and the initial guide wire is left in place through the sheath as a safety guide in the beginning of lithotripsy. Its later removal facilitates the removal of stone fragments.

The preferred puncture site is a supracostal puncture at the 11th intercostals space, bounded laterally by the posterior axillary line and medially by a line projected from the tip of the scapula. This puncture site has the advantage of hitting the middle calyx, without resorting to an oblique tract, while posing minimal risk of injury to the perinephric organ. This also contributes significantly to the subsequent improved maneuverability of the endoscope as there is minimal impingement of endoscope movement by the abdominal wall. The tract should take the shortest route through the renal parenchyma to the stone or the destination calyx, usually the middle calyx, but the actual selected calyx is tailored to the stone location and calyceal configuration. Maximal intrarenal access can be achieved via the “neutral position” of the midcalyceal puncture as the endoscope can swing a full arc. With the small sheath and miniaturized endoscope, it is normally possible to inspect the renal pelvis, upper and lower calyx, and the proximal ureter up to L4 in MPCNL, which would be impossible using the large rigid renoscope as it would bring severe torque on the tissue, risking parenchymal tear. Also, it increases the possibility of cleaning the stones from a single percutaneous tract. The strategy of stone-fragment removal by irrigational flushing avoids the tedious process of picking up every fragment with forceps, explaining why operating time in Chinese MPCNL can be much shortened. The small size of the ureteroscope, together with a straight, short tract through the abdominal wall, allows access to most calyces and the upper ureter as far down as the L4 level, which improves the clearance rate. Only the parallel calyx with an acute angle to the puncture calyx may be inaccessible, and if necessary, an additional tract can be inserted as required. There is concern about the safety of this use of pressurized irrigation. High renal pelvic pressure would result in systemic absorption of irrigation fluid, containing bacteria or endotoxin, which might then lead to postoperative fever. We inspected the renal pelvic pressure (RPP) in vivo during MPCNL. In our study, renal pelvic pressure generally remained lower than a level to back-flow (30mmHg) during MPCNL via 14-18Fr percutaneous tract. Any factors which create bad drainage would result in a temporal elevated RPP greater than 30mmHg, and a temporary high pressure status would have an accumulated effect, meaning enough back-flow to cause bacteremia and postoperative fever. Thus, we concluded that pressurized continuous irrigation through the working channel of an 8/9.8Fr ureteroscope was safe. Clinically, we did not notice a high septic rate in our study.

Modern instrumentation and technical improvement have revitalized MPCNL. The previous difficulty in stone fragmentation and stone removal has been solved. Now, MPCNL has a much wider application. Our experience showed that it could be applied to large stone loads, including staghorn calculi, with comparable operating time and clinical stone-clearance rate and complications to standard PCNL.

Written by:
Guohua Zeng and Wen Zhong as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510230, China
Guangdong Key Lab of Urology, Guangzhou 510230, China

Correspondence: Guohua Zeng
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Treatment of upper urinary calculi with Chinese minimally invasive percutaneous nephrolithotomy: A single-center experience with 12,482 consecutive patients over 20 years - Abstract

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