Endoscopic Replacement of the Amplatz Sheath with a Larger One,for Larger Stone Fragments Extraction

Introduction

U sually, for percutaneous nephrolithotomy (PCNL), the tract is dilated to 30F to accommodate a 30F Amplatz sheath for the use of a large rigid nephroscope. ¹ Nevertheless, with the advent of miniature nephroscopes, smaller Amplatz sheaths may be used. In fact, the use of a large Amplatz sheath with a smaller nephroscope leads to large outflow of irrigating fluid, which may lead to retraction of the pelvi-calyceal system, reduced visibility, and difficult inspection. Actually, we routinely use a 20.8F nephroscope (Richard Wolf) and a 24F working sheath. However, sometimes a large stone is difficult to fragment. Therefore, the replacement of the working sheath with a 30F sheath would allow more rapid extraction of larger stone fragments.

Technique

The skin incision, around the working sheath, is widened by an additional 2 or 3 mm. The 30F sheath is back-loaded over the nephroscope (Fig. 1A). Then, the nephroscope is introduced into the 24F sheath (Fig. 1B). Thus, the 30F sheath is progressively inserted in a rotating screw-type fashion, over the 24F sheath. The whole procedure is performed under direct endoscopic vision by the nephroscope, which controls that there is no forward displacement of the inner sheath (Supplementary Video; Supplementary Video is available online at www.liebertonline.com/end). When the outer sheath reaches the caliceal cavity, a bi-prong forceps, advanced through the operating channel of the nephroscope, is opened beyond the 24F sheath. Then, the nephroscope is progressively retrieved by dragging along this inner sheath (Fig. 2). This replacement of the sheath is usually performed when there is a large stone burden, difficult to fragment with ultrasound lithotripsy; and ballistic lithotripsy produces large chunks of stones. In such cases, the 24F sheath is usually blocked against the stone to prevent its forward displacement (Fig. 3). Second, this technique may be used for the same indications as the technique of splitting the Amplatz sheath to facilitate percutaneous stone extraction. ² This is helpful when there are multiple stones about 1 cm that may pass through the large sheath without fragmentation. In this case, the 24F sheath is usually introduced in the renal pelvis and oriented toward the uretero-pelvic junction. Thus, there is sufficient room if there is a sheath displacement. Further, if the stones are slightly larger than 1 cm, then the 30F sheath can be split before insertion, so both techniques can be associated. The last and infrequent situation is when the tip of the Amplatz sheath is damaged (Fig. 3).

OPEN IN VIEWER

FIG. 1.

(A) A light-gray 30F sheath is back-loaded over the nephroscope. (B) The nephroscope is introduced into the dark-gray 24F working sheath. Then, the 30F sheath is advanced progressively over the 24F sheath.

OPEN IN VIEWER

FIG. 2.

The 24F sheath is removed by an opened bi-prong forceps, placed through the operating channel of the nephroscope. (A) Endoscopic view, a light-gray 30F sheath, and a crescent of a dark gray 24F sheath. (B) Outside view, the 24F sheath is removed.

OPEN IN VIEWER

FIG. 3.

The 24F sheath is usually blocked against the stone to prevent its forward displacement. The tip of the Amplatz sheath has been damaged, which will hinder further stone extraction; so, the sheath has to be replaced.

After sheath exchange, if visibility is reduced, the flow of the irrigating fluid can be increased by putting pressure on the saline bag. Otherwise, the urologist's left hand grasps the Amplatz sheath and nephroscope, with index and thumb round the nephroscope shaft, blocking the sheath entrance, to overcome the large outflow of irrigating fluid. The difference between the outer diameter of the small sheath and the internal diameter of the 30F sheath is only 2F, which is large enough for the 30F sheath to slide smoothly. In addition, it is small enough not to cut the renal parenchyma between the two sheaths, which was not noted in any case.

For the first 10 cases, this replacement technique was also performed with the help of fluoroscopic guidance. However, to reduce radiation exposure, it is no longer used, as no migration of the 24F sheath was noted. Moreover, in more than 30 patients, no hemorrhage or renal pelvis perforation was noted, nor any complication related to the technique. This sheath replacement technique can be useful to urologists who use small-diameter working sheaths, as it may be used with other sheaths diameters, for example, 18 and 24F sheath. Therefore, in our experience, sheath exchange is a useful technique that adds more comfort and versatility during PCNL.