Percutaneous nephrolithotomy (PCNL) is usually performed in standard prone, semisupine, flank, or complete supine (csPCNL) position. Correct patient positioning is mandatory to facilitate the procedure and prevent complications. When compared with other positions, the csPCNL offers the potential advantages of less patient handling, the need to drape only once, less risk of colon injury, and the ability to perform simultaneous PCNL and ureteroscopic procedures. If PCNL is performed initially with spinal or regional anesthesia and general anesthesia is needed, the change is easier in this position. The supine position allows better access to the airway and may be less hazardous than other positions, especially for patients with compromised cardiopulmonary function, morbid obesity, or those who require a prolonged procedure. There is better drainage with the Amplatz sheath, and stone fragment evacuation is facilitated. The benefits of ultrasound-guided PCNL include no exposure to radiation for the patient or operating room staff, no need for dye materials, and no chance for injury to the surrounding tissues and organs. In ultrasound-guided PCNL, all of the tissues between the skin and kidney can be visualized directly. The present authors performed csPCNL with a subcostal upper-pole puncture and found that the kidney is situated lower than it is located in the prone position. As a result, access to the upper pole is feasible and associated with less complication. Overall, csPCNL is safe, effective, and suitable for most patients. Literature on csPCNL, imaging modalities, tract creation, tubless PCNL, and mini-PCNL is reviewed.
KEYWORDS: Percutaneous nephrolithotomy; Supine surgical position; Sonography; Imaging; Body mass index (BMI); Upper pole access
CORRESPONDENCE: Siavash Falahatkar M.D., Guilan University of Medical Sciences, Urology Research Center, Razi Hospital, Sardare Jangal Street, Rasht, Guilan 41448, Iran ().
CITATION: UroToday Int J. 2010 Apr;3(2). doi:10.3834/uij.1944-5784.2010.04.03
ABBREVIATIONS AND ACRONYMS: BMI, body mass index; CT, computed tomography; csPCNL, complete supine percutaneous nephrolithotomy; ESWL, extracorporeal shock wave lithotripsy; NT, nephrostomy tube
In the past 3 decades, percutaneous nephrolithotomy (PCNL) has been performed with the patient in various positions. These positions include standard prone, semisupine, flank, supine with a pad under the leg or buttock, and complete supine.
Although supine PCNL has numerous advantages and is routinely used in some surgical centers throughout the world, its popularity is still minimal in the field of urology as a whole. This general lack of acceptance most likely stems from fear of colonic injury during this procedure and from a lack of training in this position from educational centers. Valdivia-UrÃa  reported that from his point of view, PCNL performed with the patient in the supine position offers such a wide variety of advantages that he did not understand why the majority of urologists insist on following other routines.
Correct patient positioning for PCNL is mandatory to facilitate the procedure and prevent respiratory problems, neurologic damage (eg, brachial plexus injury), and adjacent organ injury . PCNL performed with the patient in prone position has some disadvantages, including patient discomfort or circulatory and ventilatory difficulties, especially in obese patients . Prone positioning is considered a risk factor for vision loss because it increases intraocular pressure (IOP), which decreases perfusion pressure to the optic nerve . Direct pressure to the periorbital region of the eye can cause increased intraocular pressure and blindness as the result of central retinal artery occlusion . The necessity for position changes during the procedure is another disadvantage, because placement of a ureteral catheter is commonly done in the lithotomy position before turning the patient to prone . Because anesthesia is administered with patients in the supine position, turning them to the prone position can be time consuming and not without the risk of neck or limb injury or dislodgement of the endotracheal tube. Sometimes it is impossible for the patient to lie prone because of a body habitus such as ankylosing spondylitis, severe lordosis or kyphosis, or hip or lower limb contractures .
PCNL in the supine position has been shown to have a number of advantages over other positions for both patients and surgeons. The purpose of the present article is to review literature on the supine position for PCNL and to share the experience of the authors with this procedure.
The authors used all available databases, including PubMed/Medline (US National Library of Medicine), and Embase Biomedical Database® (Elsevier; Amsterdam, Netherlands), to search for any articles related to PCNL in the supine position. They used the keywords percutaneous nephrolithotomy, supine position, sonography, imaging, BMI, tubeless, upper pole access, previous open renal surgery, and tract creation in various combinations.
For all articles where supine PCNL was used, information was gathered about the total number of patients, male to female ratio, age, maximum stone diameter, affected side, positive history of extracorporeal shock wave lithotripsy (ESWL), previous open or percutaneous surgery, body mass index (BMI), operative time, length of hospital stay, stone free rate, calyx puncture site, transfusion, extravasation, fever or infection, conversion to open surgery, deep vein thrombosis, pleural effusion, colon injury, and mortality.
Complete Supine Percutaneous Nephrolithotomy (csPCNL)
PCNL is a well known surgical procedure. The authors perform it in the complete supine position without any towel under the patient's flank and with no change in leg position . The steps of csPCNL in a 66-year-old female with multiple stones in the right kidney are illustrated in Figure 1a, Figure 1b, Figure 1c, Figure 1d, Figure 1e, Figure 1f, Figure 1g, Figure 1h, and Figure 1i.
Results of the Literature Review
The results of the literature search for PCNL procedures done with patients in the supine position [2,3,6,7,8,9,10,11,12,13,14,15] are summarized in Table 1. There were a total of 1523 patients studied. PCNL with the patient in a supine position was used to remove stones in a wide range of sizes. The majority of patients studied did not have a positive history of ESWL, but many had previous open or percutaneous surgery. The mean operative times spanned a wide range, from 15 to 300 minutes. The stone-free rate ranged from 70.5% to 95% of patients. The lower calyx puncture site was the most commonly used. Blood transfusion was needed in 0-20% of the patients. Extravasation occurred in < 12% of the patients. Fever was the most common complication. Only 3 of the 1523 patients were converted to open surgery, and there were sporadic, rare reports of deep vein thrombosis and pleural effusion. There were no reports of colon injury or mortality.
Advantages of csPCNL
Advantages for the Surgeon. When compared with other positions, csPCNL offers the potential advantages of less patient handling, the need to drape only once, and easier access to the urethra. If PCNL is performed initially with spinal or regional anesthesia and general anesthesia is needed, the change is easier in this position. The supine position allows better access to the airway and may be less hazardous, especially for patients with compromised cardiopulmonary function, morbid obesity, or those who require a prolonged procedure. Access to upper calyces in this method is easier than the prone position . There is better drainage with the Amplatz sheath, and stone fragment evacuation is facilitated. If required, a more familiar approach for simultaneous ureteroscopic access is readily obtained, allowing combined percutaneous nephrolithotomy and ureteroscopy for management of complex stone disease . In csPCNL, the puncture site for access is the posterior axillary line, which is far from the fluoroscopy tube. Therefore, the space is open for the surgeon to work and the surgeon can perform the procedure from a more comfortable seated position. Additionally, in the complete supine position the density overlap with vertebrae that occurs in the semisupine position is not observed. The patient's position on the operating table during csPCNL can be near the edge of the table, but kept a safe distance from the metal density of the work surface to minimize interference during imaging. These advantages result in reduced overall operative time when compared with the traditional prone position.
Advantages for the Patient. When compared with other positions, csPCNL offers many advantages for the patient. A supine position is more comfortable for the patient, which might result in the use of less anesthesia. Risk of hypothermia is reduced because there is little irrigation fluid falling on the patient. Because the kidney is in its normal anatomical position, anterior kidney displacement is less common than in the modified supine position  or prone position. There is also less risk of colon injury. Patients with pulmonary or cardiovascular disease have a higher tolerance for surgery when placed in the supine position.
In summary, csPCNL is safe, effective, and suitable for most patients . It is an appropriate option for patients with all types of stones, including calyceal, pelvic, multiple, staghorn, or upper pole calyceal stones.
Imaging Modalities for Percutaneous Access
Despite its short age, the scope of endourology has been widened and its success rate has increased because of medical engineering . Access to the collecting system is the first step in percutaneous interventions such as PCNL and endopyelotomy. Access is usually achieved using fluoroscopy, ultrasonography, or computed tomography (CT) guidance [17,18].
The development of imaging was essential in the progression of endourology, because the innovation and progression of PCNL was impossible without fluoroscopy . Fluoroscopy was the first imaging technique used. However, because of x-ray radiation exposure associated with fluoroscopy during PCNL for entrance into the collecting ducts of the kidney and the frequency with which this procedure is performed, the use of an alternative method to reduce the risk of radiation exposure to the surgeon and operating room staff was considered of value to the urological community.
Ultrasonography is one imaging method that is an alternative to fluoroscopy [19,20,21]. Montanari and colleagues  described the insertion of a nephrostomy tube under both fluoroscopy and ultrasonographic guidance, with a success rate of 98%. Basiri et al  compared fluoroscopy and ultrasonography in a clinical trial and concluded that access for PCNL using ultrasound guidance is an acceptable alternative to fluoroscopy. They found less radiation exposure with ultrasonography, and success and complication rates comparable with those of fluoroscopy. Hosseini et al  started prone PCNL with ultrasound guidance in 39 cases. They showed that ultrasound-guided PCNL can be a feasible, reliable, safe, and effective alternative to fluoroscopy in experienced hands. The present authors also found that the success rate of gaining access to the collecting system under ultrasonographic guidance was similar to that of fluoroscopy-guided access.
Advantages for the Surgeon. When compared with fluoroscopy, ultrasound-guided csPCNL has the advantages of elimination of x-ray exposure to the surgeon and staff in the operating room, avoidance of contrast material administration, and decreased energy expenditure for the surgeon and other staff of the operating room because there is no need to wear a lead shield. Additionally, in ultrasound-guided PCNL all of the tissues between the skin and kidney can be visualized directly; with fluoroscopy, only areas where dye has been injected can be seen.
Advantages for the Patient. The benefits of ultrasound-guided PCNL include that there is no exposure to radiation, no need for the use of dye materials, and no chance for injury to the surrounding tissues and organs. Ultrasound-guided PCNL is safe and feasible for patients with previous renal surgery .
Disadvantages. Ultrasound-guided csPCNL without fluoroscopy has some disadvantages. One problem is the use of lubricant gel on the sonography probe at the time of dilatation, which can be resolved by cleaning the hands. A second problem is that urologists are unfamiliar with sonographic images of the kidney. Because the Amplatz dilatator and Amplatz sheath echo do not have good imaging quality, the experience of the surgeon plays a large role in finding the best access. The present authors have found that urine drops help to locate the entrance to the calyceal system. Finally, sometimes the path of the guidewire is lost because of the poor quality of the guidewire echo. To avoid this complication, the authors use the more rigid Rouche guidewire for these patients. This type of guidewire is better for dilatation and helps the surgeon stay on the right path.
Computed Tomography (CT)
Another imaging method that is an alternative to fluoroscopy is CT. This technology is rarely used for PCNL because it is not available in the operating room. Radiation exposure with the CT scan may be greater than exposure during fluoroscopy. CT is also an expensive imaging modality.
Schieszer  showed that cone beam CT enables reconstruction of cross-sectional or 3D images from rotational fluoroscopy, thus adding significantly improved spatial resolution over routine planar imaging alone. This technology is superior to routine intraprocedural fluoroscopic or digital planar imaging in assessing postprocedural stone burden. Schieszer concluded that the cone beam CT allowed the surgeons to more accurately determine the location of the percutaneous access. It also allowed for more accurate assessment of residual stone burden within the renal collecting system. By adding the cross-sectional component of cone beam CT, the authors found that they were able to more effectively evaluate the access and stone clearance when compared with conventional 2-dimensional planar imaging alone.
Percutaneous Access without Imaging
Percutaneous access without imaging is a final alternative. However, blind access is reserved primarily for emergency situations and relies on known anatomic landmarks.
Supine PCNL for Upper Calyceal Stones
Percutaneous access to the upper pole of the kidney is being performed with increasing frequency. However, it carries the risk of potential pleural or parenchymal lung injury . Patients with a supracostal nephrostomy tube (NT) typically have more discomfort and pain postoperatively than patients with an infracostal NT [26,27,28].
The present authors performed csPCNL with a subcostal upper-pole puncture and found that the kidney is situated lower than it is located in the prone position. As a result, access to the upper pole is feasible and associated with less complication . The subcostal approach to the upper calyx in the prone PCNL has been shown to be more difficult [30,31]. Subcostal access with renal displacement makes the superior calyx accessible while avoiding intrathoracic complications.
Upper intercostal access is routinely achieved, but it is associated with pulmonary complications. In csPCNL, subcostal access to the upper calyx is feasible, so pleural injury can be minimized. Upper pole PCNL with a subcostal approach seems to be a new, valuable treatment option for complex stone disease [29,31].
Supine PCNL and Body Mass Index (BMI)
Obesity and morbid obesity confer an increased risk of morbidity because of their association with diabetes, cardiovascular disease, and respiratory disease . It is clear that obesity plays a role in the various methods of stone treatment . Shockwave lithotripsy is usually not efficient in treating upper urinary tract stones in obese patients [34,35].
Many authors have evaluated the safety and outcome of PCNL in the prone position in obese patients [29,32,34,36,37]. Results have shown that the outcome of PCNL is independent of the patient's BMI.
Supine PCNL has been found an effective and safe procedure in high-risk and obese patients with the patient in the supine position. It allows simultaneous management of renal and ureteral stones . The present authors have found that anesthesia time increases with an increase in BMI. However, they agree that the outcomes of PCNL in both prone and supine positions are independent of the patient's BMI. Therefore, both prone and supine PCNL in obese and morbidly obese patients are safe and effective.
PCNL for Patients with Previous Open Renal Surgery
Patients with previous open nephrolithotomy have retroperitoneal scar tissue around the kidney and distortion of the pelvicaliceal anatomy, suggesting that PCNL may be more difficult or result in a higher complication rate . This hypothesis was confirmed in one study that showed higher failure rates of PCNL in patients with prior open renal surgery . In contrast, results of subsequent studies suggest that previous open surgery for renal calculi does not affect the results of subsequent PCNL [39,40,41,42].
In conclusion, the majority of studies show that PCNL is effective and safe in patients who previously underwent open renal surgery. Efficacy results and complications of PCNL in patients with prior open renal surgery were similar to those for patients with no prior renal surgery, even if patients had multiple stones. Further, multiple tract PCNL in patients with previous renal surgery was safe. A study by the present authors  showed that the only difference between the patients with and without previous renal surgery was the duration of step 1 of dilatation. They recommend fasciatum in PCNL in patients with previous renal surgery and difficulties in dilatation caused by adhesion and fibrosis. The authors found no differences between PCNL in the prone or supine position for these patients.
Tract Creation in PCNL
Dilatation of the tract may be achieved by many different techniques, including Amplatz sequential fascial dilators, metal telescopic dilators, and balloon dilators. Balloon dilation is regarded as the most modern and safest system, but it has the disadvantage of relatively high cost. Dilation with the Amplatz set has moderate costs close to those of balloon dilation. Dilation with metal telescopic dilators is the least expensive procedure. Both of these multiple incremental dilation techniques are more time consuming and require longer exposure to radiation. Some studies have shown that dilation techniques requiring only limited passages or a single step may be safe, cost effective, require less x-ray exposure, and be less time consuming than other techniques [38,43].
The present authors also demonstrated that the one-shot technique was feasible and safe, and it reduced x-ray exposure time during the procedure . It was effective even in patients with a history of open stone surgery. Three (3.9%) of the 102 patients receiving the one-shot technique were unsuccessful. Two of the 3 patients had a past history of open renal surgery and heavy resistance of facial layers, which prevented fascial dilator passage. Kidney hypermobility and rotation during dilation prevented use of the one-shot technique in the other case.
Frattini et al  showed that one-shot dilation was unsuccessful in 2 patients (N = 26) who had a history of open stone surgery. They noted that these features represented real contraindication to the one-shot technique. Open nephrolithotomy leads to retroperitoneal scars around the kidney that may adversely affect introduction of the access needle and prevent proper dilation of the tract, necessitating the use of metal and balloon dilators [46,47].
One-shot dilation does not lead to more hemorrhagic complications than multiple incremental techniques. In a study by the present authors , 3 of the 102 patients (2.9%) required transfusion. This result was not significantly different from previously reported results .
In conclusion, one-shot dilation has proven to be as safe and effective as metal telescopic dilation, even in patients with a history of ipsilateral open renal surgery. It has the added advantage of reduced x-ray exposure time . The present authors have found that the results are the same when performed with the patient in the prone or supine position.
In several different investigations, tubeless PCNL was found to be a safe and effective method that reduces postoperative hospital stay and pain [48,49]. It can be used to treat staghorn calculi, even with multiple access tracts. Hemostatic agents are not needed, but it is recommended that the procedure should be done only by experienced surgeons. It should be avoided in patients with significant hemorrhage, significant perforation of the collecting system, a large residual stone burden, or ureteral obstruction.
There are few published studies using tubeless PCNL with multiple access tracts for treatment of staghorn stones. However, the present authors have performed this procedure and found it safe, with no significant complications. They found that the results of tubeless PCNL in csPCNL are similar to the results in the prone position [30,31]. The present authors believe that nephrostomy tube placement indications are severe hemorrhage and significant extravasation such as pelvis or ureteral perforation.
Mini-percutaneous Nephrolithotomy (Mini-PCNL; MPCNL)
Helal and Jackman developed the mini-PCNL for the treatment of pediatric renal lithiasis in 1997. Since then, various authors have used this technique in adults with the aims of preserving renal parenchyma and diminishing morbidity associated with the standard PCNL. Morbidity associated with the mini-PCNL seems to be lower than with the standard PCNL. However, the use a smaller caliber tract with the only aim of preserving renal parenchyma does not offer advantages. It is a complementary technique to the standard PCNL; however, the diameter of the percutaneous access is not yet well defined and depends on the caliber of the instruments used .
In another study, Monga and Oglevie  described the miniaturization of PCNL with a laser. The laser allowed the authors to maintain a high level of efficacy while minimizing the possibility of renal parenchymal damage.
Future Research Needs
Clinical trends for PCNL include using:
- A flexible ureteroscope to gain access to kidney
- Ultrasonography as the only imaging tool
- Smaller instruments to preserve renal parenchyma
- Telerobotic surgery
Additional research is needed to show the efficacy of these clinical developments. However, the research support for using csPCNL seems sufficient for this position to be more widely adopted by surgeons.
Conflict of Interest: none declared
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