Percutaneous nephrolithotomy (PCNL) was initially described as a procedure to be performed in the prone position in 1976, and remained a prone-only procedure for 2 decades until the description of supine PCNL in 1998. ¹ The most recent global study on PCNL (nearly 10 years old) reports the proportion of PCNLs worldwide by position as 80% prone and 20% supine. ¹ At present, PCNL position debates are a feature of many urology congresses, where debaters argue the merits of their preferred position as well as the downsides of the opposite.

Figure 1. Patient position for supine PCNL with landmarks noted. Note that degree of torso angulation is <20 degrees because surgeon’s fist cannot fit fully beneath patient in this example.

Figure 2. Preoperative CT with arrow marking safe puncture tract for supine PCNL. Note arrow is angled to accommodate for torso rotation <20 degrees during procedure.

Figure 3. Ultrasound (posterior to PAL) is performed to determine safe puncture tract. Once safe image is acquired, position of ultrasound probe on skin is marked with a line, and initial puncture is performed along that line.

Figure 4. Small amount of torso angulation that is typical of supine PCNL positioning will result in fluoroscopic image where kidney appears closer to spine than it appears when performing standard prone fluoroscopy.

As a resident and fellow, I observed and learned only prone PCNL. However, certain aspects of supine PCNL appealed to me as potentially advantageous compared to prone PCNL. These include but are not limited to 1) ease of performing endoscopic combined intrarenal surgery, 2) increased success of treatment of upper pole stones from a lower pole puncture, 3) less variation in hemodynamic parameters and 4) decreased risks of ventilation and general anesthesia, especially in overweight and obese patients. ² With these in mind, I began performing supine PCNL in 2016, starting with the most straightforward PCNL procedures. As I continued to realize the aforementioned advantages of the supine position, the proportion of supine PCNL procedures in my own practice rose gradually from around 25% in the first year of incorporation to nearly 90% at present. It is important to acknowledge that although I believe there are advantages to supine PCNL (when the position is feasible), several recent meta-analyses have failed to report that 1 position is definitively superior to the other in terms of stone-free rates or complication rates. ^3,4 Following are some lessons learned from the perspective of a surgeon trained in prone PCNL who has adopted supine PCNL for the majority of PCNL procedures.

Lesson 1. For patient positioning, the patient should be close to the lateral edge of the bed on the operative side, and ideal body rotation angle is <20 degrees. ² It is tempting for those inexperienced with supine PCNL to overrotate the patient, but increased rotation can make fluoroscopy images difficult to interpret. Anatomical landmarks include the ribs, the anterosuperior iliac spine (ASIS) and the posterior axillary line (PAL). Puncture posterior to the PAL minimizes the risk of intestinal injury (fig. 1).

Lesson 2. The simplest supine PCNL puncture technique is to begin with a puncture that is parallel to the floor of the operating room. Before the procedure, review of the preoperative computerized tomogram (CT) can help determine if supine puncture is safe and will avoid injury to adjacent structures. During the procedure, ultrasound can be used to determine the skin site of puncture that enables a puncture parallel to the floor (if performing fluoroscopy guided puncture); otherwise, ultrasound can be used for the entirety of the puncture (figs. 2 and 3).

Figure 5.Left panel, arrow denotes supine upper pole puncture tract. This patient would be safe for supine upper pole PCNL. Right panel, arrow denotes supine puncture tract. For this patient, there is significant risk of transsplenic puncture for supine upper pole puncture, whereas more medial upper pole puncture in prone position would decrease risk of splenic injury.

Lesson 3. Even a mild rotation of the torso will make the kidney appear closer to the spine on fluoroscopic images. This can be off-putting or anxiety-provoking for the surgeon who is accustomed to interpreting standard anteroposterior fluoroscopic images of nonrotated patients in the prone position (fig. 4).

Lesson 4. The kidney can be more mobile in the supine position and, as such, puncture technique must sometimes accommodate for this. This phenomenon seems to be greatest for patients with body mass index <25 kg/m ². Application of manual abdominal pressure (by the surgeon’s or assistant’s hand) or placement of a guidewire into the bladder (or out of the urethra) are techniques that have been suggested for patients with significant renal mobility. ² Studies have not been successful in quantifying the relative increased mobility of the kidney in the supine vs prone position; neither have they been able to demonstrate that increased mobility leads to changes in success rates or complications of supine PCNL. ⁵ Nonetheless, it is an important consideration, and this increased kidney mobility may result in the need for rapid, real-time adjustment of the needle trajectory in order to achieve the desired puncture.

Lesson 5. Upper pole puncture is feasible in the supine position in the majority of patients. A recently reported multicenter study demonstrated the safety and feasibility of supine upper pole puncture. ⁶ However, the prone position enables the surgeon to achieve a puncture that is in a more medial position on the patient’s flank (ie closer to the spine) than the supine position. For a small subset of patients, those with retrorenal liver, spleen or colon, the safest window for puncture is via the upper pole and close to the spinal column, and the prone position may be the safest position for PCNL (fig. 5).

Lesson 6. My own personal journey in incorporating supine PCNL into my practice has helped me understand the following: There is no “correct” or “superior” position for PCNL. Advocates of each position can and continue to make cogent arguments and debates in support of either position. As with many topics in endourology (eg stented vs stentless ureteroscopy, standard vs mini-PCNL, use or omission of ureteral access sheath during ureteroscopy), patient characteristics, surgeon experience and surgeon preference inform the choices that are made in the operating room. The goal of any procedure is to optimize success while minimizing complications. Personally, I believe that my patients and I have realized many of the theoretical benefits of supine PCNL mentioned above, which explains the high percentage of supine PCNL procedures in my practice. I do, however, perform prone PCNL for patients such as those described in Lesson 5 above, where anatomical considerations favor the prone position.