Randomized and prospective trial comparing tract creation using plasma vaporization with balloon dilatation in percutaneous nephrolithotomy

Authors


Sir,

I read with keen interest the article Chiang and Su [1]. The authors should be congratulated for an excellent study wherein they have described a novel method of tract creation for percutaneous nephrolithotomy (PCNL). They have presented a large experience in this interesting new technique for tract creation and compared it with standard balloon dilatation of the tract. We would, however, want to voice our reservations about this technique.

Tract creation for PNCL is indeed the most vital part of the PCNL procedure. The success of the procedure and complications are dictated by the access we make. Plasma vaporization by transurethral resection in saline is an established technique for the management of benign enlargement of the prostate. For this condition, the aim is to remove the obstructing prostatic adenoma, hence vaporization of the tissue is a safe alternative. By contrast, during PCNL, vaporizing the renal parenchyma to make access appears to be overkill. During the making of a tract by balloon dilatation, a space is created in the renal parenchyma without damaging the functioning nephrons by radial dilatation of the nephrostomy tract.

The authors claim that there is no change in estimated GFR after the operation in either of the two groups. They hypothesize that diathermy to the renal parenchyma would not cause more renal parenchymal or function loss with plasma vaporization than with balloon dilatation. This would need to be proven by performing a DMSA scan after 6–12 months. In view of the depth of penetration of 1 mm by plasma vaporization [2], heat dissipation in the parenchyma and coagulation of the end arteries of the renal parenchyma, the parenchymal loss could be substantially higher with plasma vaporization than with balloon dilatation.

We also foresee a few more difficulties:

  1. Fluid extravasation that may happen during plasma vaporization of the tract can lead to increased serum chloride levels with changes in base excess, serum potassium, haematocrit and central venous pressures [3].
  2. There is a risk of fragmentation and breakage of the glidewire with plasma vaporization [4]. This could make further tract-making very difficult.
  3. The Teflon covering of the wire may become eroded by electrovaporization and may make the wire electroconductive [5]. Transmission of the electric current down the ureter by the glidewire may have significant long-term complications.
  4. Making a second tract in patients, where indicated, may be difficult with plasma vaporization.

Although even balloon dilatation has its shortcomings, we still propose it is advisable to use a technique that uses radial compression for tract-making (balloon dilators or alkens or Amplatz dilators) rather than an ablative plasma tissue vaporization technique.

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