Secondary Logo

Journal Logo

Is mini-percutaneous nephrolithotomy the way to go for renal stones? No!

Knoll, Thomas

doi: 10.1097/MOU.0000000000000614

Urologische Klinik, Klinikum Sindelfingen-Boeblingen, Sindelfingen, University of Tuebingen, Germany

Correspondence to Thomas Knoll, MD, PhD, MSc, Department of Urology, Klinikum Sindelfingen-Böblingen, Arthur-Gruber-Street 70, 71065 Sindelfingen, Germany. Tel: +49 7031 9812501; fax: + 49 7031 9812342; e-mail:

Miniaturized percutaneous nephrolithotomy, often called mini-PCNL, was first described as a technique in children, by using a peel-away sheath and an ureteroscope [1]. Others have further developed the technique with specially designed small scopes, following the idea of reduced morbidity by reducing the size of the access tract [2,3]. The available armamentarium reaches from 4.85 F needle scopes to 22 F systems that are not far away from what is called standard or conventional PCNL, usually with outer sheath diameters of 24 F or larger [4–6]. Unfortunately, a marketing-triggered confusing terminology is used, introduced by the inventors using superlatives like ‘super’ or ‘perfect’ or T-shirt sizes like XL, L or S [7]. More precisely, one should rely on the size of outer diameter of the percutaneous sheath, that gives more objective information. It is important to recognize, that miniaturization is not just reducing the diameter. The smaller sizes require several modifications of the technique, including dilatation, lithotripsy or exit strategy. Furthermore, although the hypothesis seems to be convincing, there is no automatism that the procedure becomes less invasive by reducing the tract size. Terms like ‘minimalinvasive nephrolithotomy (MIP)’ are misleading [8], as the concept of percutaneous stone surgery is minimally invasive since its introduction – why it has terminated the age of open stone surgery almost 40 years ago [9]. Many factors impact the outcome of the procedure, as stone characteristics, puncture and dilatation technique, and of course, surgical skills. It is surprising, that many surgeons push mini-PCNL forward as a new standard, though only few studies support such statements [4]. An EAU Systematic Review could recently demonstrate at best a comparable stone-free rate with miniaturized instruments compared with standard (by the cost of longer operative times), but only a tendency of a lower risk of bleeding [10]. Overall study quality was low with high risks of bias and heterogeneous groups. Moreover, miniaturized access included all sizes 18 F or less, including needlescopic access. Beyond this scepticism, chosen instruments and access shall clearly be adapted to the individual patients. Children, difficult anatomy, like diverticular stones or narrow infundibula may need smaller accesses. But does the standard patient benefit from miniaturized PCNL? This answer cannot be given yet, and no guideline gives advice on this. But what can be observed in daily practice is an increasing frequency of PCNLs in medium-sized stones instead of ureteroscopy or extracorporeal shock wave lithotripsy, justified by miniaturization. Caution is advisable considering the very weak available data supporting this concept. It is worldwide accepted, that retrograde ureteroscopy, that competes with mini-PCNL, comes with significantly lower complication risk than percutaneous surgery. Using superlatives for marketing is dishonest to our patients as it raises expectations that might not be fulfilled. Maxi complications may occur even with micro access. Size might matter, but what matters more are the right indication and a skilled surgeon.

Back to Top | Article Outline



Back to Top | Article Outline

Financial support and sponsorship


Back to Top | Article Outline

Conflicts of interest

There are no conflicts of interest.

Back to Top | Article Outline


1. Jackman SV, Docimo SG, Cadeddu JA, et al. The ‘mini-perc’ technique: a less invasive alternative to percutaneous nephrolithotomy. World J Urol 1998; 16:371–374.
2. Lahme S, Bichler KH, Strohmaier WL, Gotz T. Minimally invasive PCNL in patients with renal pelvic and calyceal stones. Eur Urol 2001; 40:619.
3. Nagele U, Horstmann M, Sievert KD, et al. A newly designed amplatz sheath decreases intrapelvic irrigation pressure during mini-percutaneous nephrolitholapaxy: an in-vitro pressure-measurement and microscopic study. J Endourol 2007; 21:1113–1116.
4. Desai J, Zeng G, Zhao Z, et al. A novel technique of ultra-mini-percutaneous nephrolithotomy: introduction and an initial experience for treatment of upper urinary calculi less than 2 cm. BioMed Res Int 2013; 2013:490793.
5. Bader MJ, Gratzke C, Seitz M, et al. The ‘all-seeing needle’: initial results of an optical puncture system confirming access in percutaneous nephrolithotomy. Eur Urol 2011; 59:1054–1059.
6. Zeng G, Mai Z, Zhao Z, et al. Treatment of upper urinary calculi with Chinese minimally invasive percutaneous nephrolithotomy: a single-center experience with 12,482 consecutive patients over 20 years. Urolithiasis 2013; 41:225–229.
7. Schilling D, Husch T, Bader M, et al. Nomenclature in PCNL or the Tower of Babel: a proposal for a uniform terminology. World J Urol 2015; 33:1905–1907.
8. Abdelhafez MF, Amend B, Bedke J, et al. Minimally invasive percutaneous nephrolithotomy: a comparative study of the management of small and large renal stones. Urology 2013; 81:241–245.
9. Alken P, Hutschenreiter G, Gunther R, Marberger M. Percutaneous stone manipulation. J Urol 1981; 125:463.
10. Ruhayel Y, Tepeler A, Dabestani S, et al. Tract sizes in miniaturized percutaneous nephrolithotomy: a systematic review from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol 2017; 72:220–235.
Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.