European Journal of Cardiovascular Medicine

PCNL (percutaneous nephrolithotomy) is the gold standard for large and complex renal calculus. It has gradually replaced conventional open surgery to merely less than 1% of cases. PCNL was first described with patient in prone position by Fernstrom and Johansson in 1976, with high success rate and acceptable low morbidity ¹. Majority of urologists prefer the conventional prone position during PCNL due to certain advantages like wide surgical field for kidney puncture site selection, and adequate nephroscopic manipulation, easier upper pole puncture with a lower risk of visceral injury, a good distension of the collecting system, feasibility to bilateral procedures, easiness to puncture the calyx, direct and shorter track length, ease of tract dilatation, ease to do multiple punctures and familiarity with the surgery. But the prone position has got several inherent problems like  difficulty of obtaining combined antegrade and retrograde access, cardiovascular and pulmonary compromise because of compression on chest particularly in the morbidly obese patients, compromised cardiopulmonary status and skeletal deformities; cervical spine injuries, tracheal compression and ocular injury during turning the patient; more fluid absorption because antigravity drainage of fluid.  As simultaneous RIRS (retrograde intrarenal surgery) is difficult and or impossible in prone position, search for more easier and comfortable access to the entire urinary system for combined antegrade and retrograde surgery, leads to development of alternative patients position for PCNL. There are several positional modifications in the technique of PCNL ^2-4. PCNL has evolved many a fold throughout the 8^th decade of 20^th century and in 1990 first original supine position was described by Valdivia et al ⁵.

In supine position the downward direction of the tract maintains low pressure in renal pelvis, and thereby reduces the risk of fluid absorption and allows spontaneous clearance and washout of fragments by gravity directed flow of fluid. In supine PCNL, as the abdominal wall is punctured more laterally, away from the lumber muscles, the movements of the endoscopic instruments are less restricted. There are other multiple benefits like avoidance of supra costal (pleural) puncture, intercostal vessel and nerve injury and simultaneous access for ureterorenoscopy for migrated or residual stones^2-4,6-8. The presumed risk of bowel and other solid organ injury has been comprehensively allayed by numerous anatomical Computed Tomographic (CT) studies ^5,6,7. Despite these advantages, supine PCNL has not gained the confidence of urologists in general. The main limitation of this position is that the flank is not fully exposed, which makes initial puncture more difficult. In 2007 The Galdakao-modified supine Valdivia position was described by Ibarluzea et al. ⁹ for supine PCNL. It was later confirmed by several authors that the PCNL in this supine position is a safe and versatile procedure with high success rates and has advantages over the prone position ^10-11. In this position the ipsilateral leg is extended and the contralateral leg is abducted and flexed. The patient is placed in an intermediate supine-lateral position with a 1 or 3-L bag placed to raise the flank. This position combines the surgical and anesthesiological advantages of the original Valdivia position with the additional advantage of combining the procedure with RIRS. Two urologists, Dr. Roberto Mario Scarpa and Dr. Cesare Marco Scoffone, from Orbassano(Torino) enthusiastic about the simultaneous endourological access, were the ones who created acronym ECIRS (Endoscopic Combined  Intra Renal Surgery). The present study aims to compare the surgical outcomes of PCNL performed using supine position with those performed in the standard prone position.

This is a randomized, double blinded, single center, prospective, experimental comparative study conducted in a tertiary care hospital in Eastern India after taking approval from the Institute Ethics Committee (IEC). All the patients had sterile urine culture before the procedure. All the patients with renal calculi of size >10 mm in age group >12 years presenting to the department of urology giving informed written consent were included in this study. Patients with age <12 years, uncontrolled coagulopathies, sepsis, pregnancy, previously operated patients and renal anomalies (such as horseshoe kidney and ectopic kidney) were excluded from this study. After considering inclusion and exclusion criteria, 120 patients with renal calculi were randomly assigned in to two groups, each with 60 patients, all demographic, clinical data, operative, and post-operative characteristics were recorded. Randomization is done by computer generated sequence. Detailed history and through physical examination were done. Preoperative evaluation was done either with computed tomography (CT urography with 3D reconstruction) or intravenous urography (IVU) along with other relevant and routine investigations and NCCT of KUB postoperatively. The variables compared between two groups (supine and prone) were age, sex, comorbidities, baseline hemoglobin, serum creatinine and grade of hydronephrosis. The stone characteristics including site, size, number, mean operative times, stone-free rate (SFR) (<4mm), postoperative hemoglobin, length of stay in hospital, and post-operative complications and requirements of second stage PCNL or ancillary procedures were also compared. Post-operative complications were classified according to the modified Clavien-Dindo grading system.

Operative steps

In prone PCNL patient is placed to prone position after ureteral catheterization which is then fixed to an indwelling per-urethral Foleys catheter. Initial puncture was done with 15 cm long 18 G puncture needle in Bulls eye, triangulation or hybrid (gradual descend) technique. A hydrophilic guide wire of size 0.035” is passed and parked in ureter and serial dilatation is done over metallic guide rod upto 22 Fr to allow Amplatz sheath of 24 Fr. Then stone is fragmented with pneumatic lithoclast and all fragments are retrieved with alligator or tripong forceps. After stone fragments retrieval, thorough inspection is done for residual stones with direct visualization and also fluoroscopic guidance. A double (DJ) stent of size 6 Fr (6/26) was placed in all cases.

In supine PCNL, patients were placed in Galdakao-modified supine Valdivia position with ipsilateral leg is extended and contralateral leg is abducted and flexed (Figure 1) and ureteral catheterization is done. Two bolsters (1litre saline bag) are placed, one under the hip and another under the chest to raise the flank. The ipsilateral arm is placed on the thorax and venous access through the opposite arm. Surface marking of posterior axillary line, 12th rib and iliac crest was done in beforehand in siting and standing position (Figure 2). Initial puncture is done with 15 cm long 18 G needle in triangulation or gradual ascend technique. Rest of the procedure is same as that of prone procedure. All patients were followed up with Non -contrast CT scan after 4 weeks of PCNL to determine stone free status (SFR). 

Data were collected, revised, coded, entered and statistical analysis was done with data analysis software SPSS (statistical package for social science)- Chi-square and Fisher’s exact test. A p value of <0.05 was taken as statistically significant.

Figure 1: Supine position with ipsilateral leg is extended and contralateral leg is abducted.    

Figure 2: Surface marking of posterior axillary, line, 12th rib and iliac crest was done in and flexed.                                          beforehand in siting and standing position.

A total of 120 patients were included in our study. In this study, male patients were 52.5 % (63) and female were 47.5 % (57).  Stones located in the right side 64 patients (53.3%) and stone was located to the left side in 56 (46.7%) patients. The mean age was 44.21±15.32 years in prone PCNL and it was 42.82±18.14 years in supine PCNL. The mean BMI was 23.24±2.68 kg/m2 and 22.68±2.86 kg/m2 in prone and supine PCNL, respectively. 38 patients (63.3%) of prone group and 35 patients (58.3%) of supine group fulfills the criteria ASA (American Society of Anesthesiologist’s) category I health status. Stone size varied from 11 mm to 53 mm with a mean stone size of 268.214±174.342 mm² in prone PCNL and 238.4±198.2 mm² in supine PCNL (Table 1). There was no significant difference in stone size between the two groups.   In prone PCNL and supine PCNL grade I Hydronephrosis 2(11%) and 2(9%) respectively. Grade II, III, IV hydronephrosis in prone and supine PCNL 6(32%) and 9(41%),7(37%) and 6(27%) and 4(21%),5(23%) respectively. Location of stones were 21(35 %) and 20(33%) in renal pelvis, 15(25%) and 18(30%) in lower calyx, 6(10%) and 7(12%) in middle calyx, 4(7%) and 3(5%) in upper calyx, and 6(10%) and 5(8 %) in multiple calyxes in prone and supine PCNL respectively.  7 patients (7%and 5%) had partial and 8 patients (7% each) had complete staghorn calculus in prone and supine PCNL respectively.

The mean intra operative time was 55-145 (85±29.28) min in prone PCNL and 50-125 (62±25.36) min in supine PCNL with a p value of 0.032. In prone PCNL, 51(85) % patients had no residual stone and 9(15%) % had residual stone. In supine PCNL, 53(88.33) % patients had no residual stone0 and 7(11.27%) patients had residual stone. The difference between the two groups was statistically insignificant with p value of 0.346. The mean post operative hospital stay was 3.52±1.03 and 3.65±1.08 days in prone and supine group respectively. 5 patients in prone PCNL and 4 patients in supine PCNL had Clavein- Dindo grade I complications and 3 patients in supine group  and 3 patients in prone  PCNL had grade II complications. The complications were fever and nausea in grade I and requirement of blood transfusion in grade II complication. The mean hemoglobin drop was 0.53 g/dl and 0.51 g/dl in prone and supine position respectively (p value >0.05). Post operative blood transfusion required in 8 patients in prone group and 5 patients in supine group. There were one serious (grade 4a) complications (fecal fistula) in supine PCNL group which was detected intraoperatively and treated with fecal diversion with prolonged (3 weeks) placement of nephrostomy tube. 2 patients require relook PCNL in prone and 1 patient in supine PCNL. ESWL require in 4 patients in prone PCNL and 3 patients in supine PCNL.

Table 1: Patients Characteristics Data

Table 2: Stone characteristics data

Table 3: Perioperative characteristics

Table 4: Clavien and Dindo Score and patients position

PCNL (percutaneous nephrolithotomy) is the gold standard for large (>20 mm), complex and complicated renal calculus. The most suitable and effective position for PCNL has always remained a topic of debate among the urologists of various countries around the world.  Initially, prone position was adopted in PCNL, but gradually supine or modified supine PCNL are gaining popularity. For a safe access to the kidney, PCNL is usually done in prone position. The prone posture position provides a number of advantages. For example, a large surgical field for puncture site selection, appropriate nephroscopic manipulation, and effective distension of the pelvicalyceal system; yet, prone position is generally linked with restricted breathing movements and risk of anesthesia ^12,13. Despite the various well-documented advantages of supine PCNL, it has failed to gain the confidence among the most urologist. This is partly due to fear of inadvertent bowel/visceral injury and partly due to the lack of a standardized technique of calyceal puncture. But in one study by Tuttle et al., employed CT scan to show that in prone position, the colon is closer to the kidney than in supine position ⁷. Desoky et al., also found that in the supine position, the mean perpendicular distance between the colon and the renal access appeared to be greater than in prone position ¹⁴. According to another research by Hopper, the retro-renal colon was discovered by CT scan in 1.9% of supine and 10% of prone patients. Hence, supine PCNL seems to have a decreased risk of colon damage ⁶. In supine position, less pressure is imposed on their lungs than prone position, especially in obese patients and those patients who have cardiopulmonary comorbidities and spinal deformities. If re-intubation is required, the supine position offers faster and better access to the airway. In supine position, patients repositioning, redraping, staff rescrubbing and regowning were not necessary unlike prone position. In supine PCNL if inadvertent dislodgement of ureteric catheter occurs, it will be repositioned without changing the position of the patients unlike prone PCNL where this advantage is absent.  A study conducted in obese patients by Mazzucchi et al., discovered that the total supine posture gives considerably lower operative durations and post-operative duration of stay in hospital ¹⁵. In supine position, intrarenal pressure is reduced due to collapse of pyelocaliceal cavity results in lower fluid absorption and fever. Fever is thought to be linked with to bacterial translocation through the lymphatic and circulatory systems ¹⁶. In supine position, access through lower calyx usually gives easy access to superior and middle calyx unless it is an acute angle so stone clearance is done with minimal need of additional puncture. According to Sofer M et al., access to superior calyx is easier in supine position than prone position ¹⁷. In a randomised study of 38 patients with upper calyceal stones Soliman T et al., concluded a better stone clearance rate with supine as compared to prone PCNL ¹⁸. Another study also claimed that better stone clearance rate and lesser complications with supine PCNL for lower calyceal stones ¹⁹. Despite supine PCNL has several advantages, it is associated with several important technical difficulties. In case of anterior calyceal stone, forming a tract directly through the anterior calyx does not pass through the area of Brodel’s avascular line and is associated with higher bleeding complications ²⁰. The distance between 12^th rib and the superior edge of the iliac crest is greater in prone than supine position. Since the puncture site lies between these two landmarks, supine PCNL may be associated with limited field, which restricts nephroscopic maneuvers and may interfere with execution of further tracts in the case of multiple- access PCNL ²¹. In supine position, the kidney is positioned more medially and is more floating in the retroperitoneum. In case of a floating kidney, wide kinking of the metallic guide wire may hamper execution of the nephrostomy tract and dilator progression in supine position ²⁰. Greater mobility of kidney may also associated with longer tract creation, decrease nephroscope mobility, greater force exertion on the renal parenchyma which may leads to increase chance of parenchymal damage and bleeding ²¹. In supine PCNL with decreased filling and collapsed pyelocaliceal system restricts the surgical field and even a moderate amount of bleeding obscure vision and may lead to early termination of the surgery.

AI-Dessoukey et al. in their comparative study had found the mean operative time was 86.16 min (standard deviation [SD]-33.7) in supine group and 111.7 min (SD-39.4) in the prone group (p<0.001) ²². In our study, we have seen mean operative time of 55-145 min (SD- 85±29.28) and 50-125min (SD- 62±25.36) in prone and supine PCNL, respectively with a p value of 0.032 which is statistically significant. Many other studies also found that supine PCNL takes significantly less operative time than prone PCNL which they attributed to the saved time taken on repositioning the patient to prone after ureteral catheterisation ^23,24. In our study there was hemoglobin (Hb) drop (difference between pre and post operative hemoglobin level) 0.53gm and 0.51 gm in prone and supine group, respectively with a p value >0.05 which is insignificant. AI-Dessoukey et al. found a difference in the mean Hb change between pre-operative and post-operative Hb (-1.03 and - 2.180 g/dl) in prone and supine positions, respectively (p< 0.001), which they attributed to obstruction of the inferior vena cava during PCNL in prone position and backflow of blood to the renal vein and may explain why bleeding in the prone is more ²². Blood transfusion rate in our study is 8 (13.3%) in prone and 5 (8%) in supine PCNL with a p value of >0.05 which is statistically insignificant. Many studies found that the rates were lower in supine than prone PCNL.  This was attributed to less intraoperative time in case of supine PCNL in their studies ^23,25. In our study, mean hospital stay was 4.64 days in prone and 4.72 in supine position, with p value 0.724 which is not statistically significant. Wang et al. in their meta analysis found that the mean hospital stay was 8.2 and 8.4 days in prone and supine PCNL, respectively with a p value 0.26²⁶. Zhang et al. also did not found any significant difference in terms of hospital stay between prone and supine group ²⁷. In our study stone free rate (SFR) checked with a noncontrast CT KUB was relatively higher in supine position (88.3%) than prone position (85%) with a p value of 0.346 which is statistically insignificant. This relative increase in stone clearance in supine position can be attributed to the gravity directed flow of irrigating fluid and thus washing out small fragments of stone automatically. Our study is in accordance to various studies like Liu et al. and Wu et al ^28,29.  Nour et al. in his study found that three patients out of 54 renal unit undergiong PCNL in supine position needed an auxillary endoscopic procedure under anesthesia ³⁰. In our study, two patients in prone and three patients in supine PCNL further require relook PCNL and three patients in prone and two patients require ESWL. In our study had an overall complication rate of 13.7%, for both prone and supine position which was similar to the literature. Most of the complications were grade 1 and 2 (fever, blood transfusion, and change of antibiotics). There were one serious (grade 4a) complications (fecal fistula) in supine PCNL group which was detected intraoperatively and treated with fecal diversion with prolonged (3 weeks) placement of nephrostomy tube. In our study we have seen that four out of seven patients in prone PCNL and two out of five patients in supine PCNL group who developed complications had BMI more than 30 kg/m ².

Supine PCNL is a  very safe, quick and effective procedure with higher rate of stone clearance as compared to prone PCNL though statistically insignificant along with similar operative times and complications. Supine PCNL also has potential advantages in high-risk patient with cardiac, pulmonary and specially morbid obese patients. It is very safe from anesthesiological point of view. It also allows for simultaneous antegrade, retrograde and sometimes bilateral access for renal and upper ureteric stones. It must remember that an urologist must have familiarity with various positions of PCNL although most suitable position can be chosen according to patients characteristic’s and surgeon’s preference and training. 

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