Editorial Comment for Zeng et al.

Zeng and colleagues ¹ report a large retrospective series of more than 10,000 patients who have been treated by what they call minimally invasive percutaneous nephrolithotomy (PCNL) for simple and complex renal caliceal calculi. The series covers a long period from 1992 to 2011. During this period, the authors modified their technique from a two-stage to a one-stage procedure, and one may assume that there are many other parameters that were changed during 20 years. The puncture was performed by ultrasonographic guidance only, without using fluoroscopy during the whole procedure. Personally, I strongly believe that a combined fluoroscopy and ultrasonography guidance is the safest approach, an impression that is supported by my own and Clinical Research Office of the Endourological Society data. ^{2 –4} The abandonment of fluoroscopy, common in China for some reasons, has potential hazards because of the loss of information (ie, perforation of the collecting system). The main tract was dilated to 18F to 20F and, if necessary, additional tracts to 14F to 18F. An 8/9.8F semirigid ureteroscope was used. The authors do not mention the principle of stone disintegration, but one may assume that different ballistic or laser-based systems were used.

The term “minimally invasive PCNL” is misleading in my opinion, because percutaneous stone surgery can generally be considered minimally invasive. Until today, the advantage of small diameter instruments in adult patients remains under discussion. Li and associates ⁵ demonstrated in a consecutive series comparing standard vs miniaturized PCNL that the reduction of sheath diameter did not lead to measurable differences in systemic response to surgery-induced tissue trauma. This might reflect only one aspect of potential side effects, however. The major complication of PCNL is bleeding induced by puncture, dilation, and manipulation. ⁶ In an own series, we could demonstrate equal efficacy and safety of mini-PCNL compared with standard 26F PCNL, ⁷ but the postoperative course of the mini-PCNL patients was better in terms of pain—most probably because of the fact that, in absence of bleeding, all mini-PCNL procedures could be performed in a tubeless fashion. Our findings were confirmed by Mishra and coworkers ⁸ who as well reported a higher rate of tubeless procedures in the mini-PCNL group. Furthermore, they could show a higher hemoglobin drop in the conventional PCNL group than after mini-PCNL. These findings support the idea that mini-PCNL has advantages in terms of tissue damage, even without measurable systemic response, especially when a perfect transpapillary puncture could not be achieved. The reduced risk of postoperative hemorrhage might be even more pronounced in multitract attempts, where the risk of bleeding increases significantly. ⁹

While miniaturized percutaneous renal surgery in adults seemed to be a German-Chinese concept in the beginning, more and more urologists all over the world have started using such instruments. The trend to further miniaturization is ongoing, and needlescopic instruments are available today. ¹⁰ Several terms are being used, however, from mini-PCNL to ultra-mini to micro-PCNL (with outer sheaths diameters from 4F to 22F). In most series, the term mini-PCNL is used for 14F to 18F tracts. There is a clear need to standardize the terminology to avoid misleading reports as published by Giusti and colleagues ¹¹ in 2007, who used smaller sheaths than usual with unmodified ureteroscopes for a procedure he called mini-PCNL.

In the current work, Zeng and colleagues report one of the largest series on miniaturized PCNL until now, demonstrating that this approach is reasonable and effective. I am looking forward to articless from other groups that confirm these findings. Apparently, mini-PCNL is here to stay.