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Technique to overcome renal mobility during percutaneous tract dilatation: bi-prong forceps renal parenchyma dissection
Version of Record online: 7 AUG 2013
© 2013 BJU International
Volume 112, Issue 5, pages 697–702, September 2013
How to Cite
Lezrek, M., Bazine, K., Asseban, M., Ammani, A., Moufid, K., Beddouch, A. and Alami, M. (2013), Technique to overcome renal mobility during percutaneous tract dilatation: bi-prong forceps renal parenchyma dissection. BJU International, 112: 697–702. doi: 10.1111/bju.12104
- Issue online: 7 AUG 2013
- Version of Record online: 7 AUG 2013
- percutaneous nephrolithotomy (PCNL);
During percutaneous renal tract creation in normally fixed kidneys, the puncture needle, dilators and sheath enter the renal parenchyma smoothly. However, when the kidney is abnormally mobile, it is pushed by the puncture needle and particularly by the dilators. Thus, when the dilators meet the resistance of the renal capsule, insisting to enter the parenchyma will lengthen the percutaneous tract . This causes wide kinking of the guidewire, making dilator progression difficult . Consequently, tract dilatation becomes time consuming with increased radiation exposure. To overcome this problem, we use a complement to ‘one-shot’ dilatation  by using bi-prong forceps to perform dissection of the renal parenchyma under direct vision and without radiation exposure.
For percutaneous surgery, the patient is placed in the split-leg modified lateral position . Tract dilatation is mostly performed directly using ‘one-shot’ dilatation with an Amplatz dilator and a 24 F sheath. In case of a mobile kidney, which is pushed by the dilator; without insisting (or persevering), the Amplatz sheath and dilator are stopped in contact with the renal capsule (Figure 1A and B). The Amplatz dilator is retrieved and the nephroscope is advanced alongside the guidewire. The renal puncture site with one or two guidewires is located (Figure 2A). The tip of the bi-prong forceps is inserted in the renal capsule breach (Figure 2B). It is then opened and used to progressively widen the renal capsule and the parenchyma tunnel by blunt dissection (Figure 3A and B). The forceps is turned 90 ° and opened once again. It is then closed and advanced into the renal tunnel. The procedure is repeated in a similar manner (Figure 4A) until the calyceal cavity is reached. The nephroscope and then the Amplatz sheath are smoothly advanced over the forceps with a rotating motion until the calyceal cavity is reached (Figure 4B). Occasionally the renal tunnel is barely dilated, even to 10 F, and the insertion of the safety guidewire is almost impossible. In this case, a forceps with a narrow tip is used until the tunnel is wide enough for larger forceps. On rare occasions the Amplatz dilator and sheath cannot even dilate the retro-renal fascia. In this case, forceps dilatation is used to widen the retro-renal fascia, and then the renal tunnel.
This bi-prong technique was initially performed in cases of stone occupying the entire calyx of entry, so as not to perform dilatation beside the stone, which might lead to calyceal or infundibular lacerations . However, this procedure was first used to surmount renal mobility in large hydronephrosis with thin renal parenchyma, where it seemed easier and safer with less haemorrhagic risk. Yet, as expected, during dilatation of large parenchyma there is bleeding and usually the calyceal cavity is occupied with blood clots . However, like with other means of dilation, the advance of the Amplatz sheath tamponade the bleeding and the clots are aspirated using the vacuum technique . In fact, once the Amplatz sheath is placed, no difference in bleeding was noted compared with other dilatation methods. Furthermore, with other dilatation systems, over-advancement of the dilator and sheath in the accessed calyx may result in significant trauma to the renal collecting system and/or excessive haemorrhage . As the dilatation in our technique is performed under direct vision, this problem of over-advancement was not noted.
A similar technique has been reported for percutaneous access to small calyceal diverticulum. After balloon tract dilatation, the working sheath is placed outside the diverticulum; then an alligator forceps is used to spread the outer wall of the diverticulum under direct vision .
The use of a balloon dilatation catheter, if it can be appropriately positioned, may indeed help to avoid the problem of renal mobility during dilatation . Otherwise, in the prone position, during a planned percutaneous nephrolithotomy in a floating kidney, Goldfischer et al.  made a single tract with insertion of a balloon catheter, which was then used to retract and stabilise the kidney, allowing accurate further punctures for stone removal. Similarly, in the supine position, Valdivia et al.  and Shoma et al.  used extra-abdominal compression during dilatation of these tracts to minimise renal movement. De Sio et al.  found that the use of a Lunderquist guidewire was particularly helpful to stabilise the kidney.
The main advantage of our technique is that the dissection of the renal parenchyma is performed under direct vision with no need for radiation exposure. In addition, it might be faster than other techniques. This technique is another addition to the urologist's arsenal, to surmount the problem of renal mobility during tract formation.
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