PNL has been performed successfully with the patient in prone position for decades. Increasingly, though, authors are reporting impressive results with different variations of the supine position [7, 8, 54, 55]. What are the potential advantages of PNL in supine or modified lithotomy position? A ureteral catheter is usually placed prior to PNL for better visualization of the renal collecting system. As this procedure is performed in lithotomy position, the patient has to be turned on the operation table into prone position. Apart from this potentially time-consuming maneuver, other limitations include the placement in prone could be limited in patients with difficult anatomy (as severe kyphosis or lordosis), the anesthesiological risk might be higher and management of anesthesia problems could be demanding, and lastly surgeons have a higher radiation exposure [7].

The major advantage of supine PNL that has contributed to the wide spread of this technique is the option of simultaneous retrograde and antegrade stone management. This technique has been established in a modified supine lithotomy position [6, 56].

Apart from this true advantage, other potential benefits of supine PNL such as decreased operating time and less anaesthesiological problems are yet to be confirmed. In contrast, de la Rosette et al. demonstrated in a meta-analysis that most peri- and postoperative parameters were comparable between prone and supine PNL [5]. For obese patients, their analysis indicates even an advantage for prone positioning. This is important, because obese patients usually have a higher ASA score and would therefore probably benefit of supine positioning and a significant portion of PNL patients is obese. Furthermore, as large renal stone burden seems to be related to obesity and the metabolic syndrome complex, these patients may be candidates for upper pole or multi-tract PNL. However, several authors have demonstrated that supracostal accesses are difficult (and often impossible) to establish in supine position [5, 57]. Another important issue to consider is the higher learning curve associated with supine PNL [7, 58].

The meta-analysis of de la Rosette et al. is in accordance to the results of the Clinical Research Office of the Endourological Society (CROES). The CROES study is the largest published database including more than 5,700 patients [41]. Very recently, Valdivia et al. have published a subanalysis investigating the impact of patient positioning on outcome and complication rate [59]. In this series, the majority of procedures were performed in prone position (80.3 %). The mean operating time was significantly lower for prone versus supine position (82.7 vs. 90.1 min.). It is important to note that the method of tract dilation had not impact on operating time. Stone-free rate was higher for prone position (77.0 % vs. 70.2 %, p < 0.0001). On the other hand, more patients received blood transfusions (6.1 % vs. 4.3 %, p = 0.026) and developed fever (11.1 % vs. 7.6 %, p = 0.001) in the prone group. Slightly more treatment attempts failed in prone position (2.7 % vs. 1.5 %, p = 0.01). Although this series impresses with the very high number patients, it is questionable whether the described differences reflect clinical reality. The data was collected in 96 global centers, with each of them having its own standards. This includes important parameters as methods to assess stone-free rates and calculating operating times. More importantly, the term supine was used for different positions, from flat supine to elevated lithotomy positions.

This underlines that the discussion on the best patient positioning is still open and further studies have to identify advantages and disadvantages of both options.