Prone Versus Supine Percutaneous Nephrolithotomy: What Is Your Position?

Image-guided surgical planning of percutaneous nephrolithotomy with patient-specific CTRs

PURPOSE

We propose the utilization of patient-specific concentric-tube robots (CTRs) whose designs are optimized to enhance their volumetric reachability of the renal stone, thus reducing the morbidities associated with percutaneous nephrolithotomy procedures. By employing a nested optimization-driven scheme, this work aims to determine a single surgical tract through which the patient-tailored CTR is deployed. We carry out a sensitivity analysis on the combined percutaneous access and optimized CTR design with respect to breathing-induced excursion of the kidneys based on preoperative images. Further, an investigation is also performed of the appropriateness and effectiveness of the percutaneous access provided by the proposed algorithm compared to that of an expert urologist.

METHODS

The method is based on an ellipsoidal approximation to the renal calculi and a grid search over candidate skin areas and available renal calyces using an anatomically constrained kinematic mapping of the CTR. Percutaneous access is selected for collision-free CTR deployment to the centroid of the stones with minimal positional error at the renal calyx. Further optimization of the CTR design results in a robot tailored to the therapeutic anatomical features of each clinical case. The study examined 14 sets of clinical data of PCNL patients, analyzing stone reachability using preoperative images and breathing-induced motions of the kidney. An experienced urologist qualitatively assessed the adequacy of percutaneous access generated by the algorithm.

RESULTS

An assessment conducted by an expert urologist found that the percutaneous accesses produced by the proposed approach were found to be comparable to those chosen by the expert surgeon in most clinical cases. The simulated results demonstrated a mean volume coverage of 81.6 % ± 19.6 % for static anatomy and 63.7 % ± 27.7 % and 69.0 % ± 25.4 % when considering a 1 cm excursion of the kidney in the craniocaudal directions due to respiration or tool-tissue interaction.

CONCLUSION

The optimization-driven scheme for determining a single tract surgical plan, coupled with the use of a patient-specific CTR, shows promising results for improving percutaneous access in PCNL procedures. This approach clearly shows the potential for enhancing the quality and suitability of percutaneous accesses, addressing the challenges posed by staghorn and non-staghorn stones during PCNL procedures. Further research involving clinical validation is necessary to confirm these findings and explore the potential clinical benefits of the approach.

Prone vs supine percutaneous nephrolithotomy: does position affect renal pelvic pressures?

The purpose of this study was to measure and compare renal pelvic pressure (RPP) between prone and supine percutaneous nephrolithotomy (PCNL) in a benchtop model. Six identical silicone kidney models were placed into anatomically correct prone or supine torsos constructed from patient CT scans in the corresponding positions. A 30-Fr renal access sheath was placed in either the upper, middle, or lower pole calyx for both prone and supine positions. Two 9-mm BegoStones were placed in the respective calyx and RPPs were measured at baseline, irrigating with a rigid nephroscope, and irrigating with a flexible nephroscope. Five trials were conducted for each access in both prone and supine positions. The average baseline RPP in the prone position was significantly higher than the supine position (9.1 vs 2.7 mmHg; p < 0.001). Similarly, the average RPP in prone was significantly higher than supine when using both the rigid and flexible nephroscopes. When comparing RPPs for upper, middle, and lower pole access sites, there was no significant difference in pressures in either prone or supine positions (p > 0.05 for all). Overall, when combining all pressures at baseline and with irrigation, with all access sites and types of scopes, the mean RPP was significantly higher in the prone position compared to the supine position (14.0 vs 3.2 mmHg; p < 0.001). RPPs were significantly higher in the prone position compared to the supine position in all conditions tested. These differences in RPPs between prone and supine PCNL could in part explain the different clinical outcomes, including postoperative fever and stone-free rates.

Supine tubeless upper pole PCNL under spinal anaesthesia: Safety, feasibility and outcomes from a tertiary endourology centre

Objective

Supine Percutaneous Nephrolithotomy (PCNL) is being taken up by many urologists in recent times, but there is a tendency to shift to prone PCNL for upper pole puncture. We analyzed the safety, feasibility and outcomes of upper pole access in Supine Percutaneous Nephrolithotomy (sPCNL).

Materials and methods

A retrospective review of all patients undergoing sPCNL at a tertiary care center was done from January 2021 to December 2022. Data collection was done from the maintained imaging, laboratory and hospital records. All cases with complete data on upper pole access were included. Data analysis was done with Xlstat2021.

Results

50 patients with upper pole access were included (64%, 32 with single access and 36%, 18 with multiple accesses). The mean stone size was 23.88 ± 9.99, mean HU was 1093 ± 232.83, and the mean operative duration was 67.92 ± 34.62. Stone clearance rate was 98.82%, with all procedures performed tubeless.The mean haemoglobin drop was 0.75 ± 0.42 gm/dl with 2 (4%) patients needing a blood transfusion. The overall complication rate was 22% with only 1 Clavien Dindo III complication (1 pleural injury and hydrothorax needing USS guided aspiration) and others being Clavien Dindo I/II complications.

Conclusion

Supine PCNL is a feasible and safe approach for upper pole access. While the procedure can be done tubeless, these procedures must be done in experienced endourology units.

Which position is more advantageous for percutaneous nephrolithotomy: supine or prone?

Percutaneous nephrolithotomy (PNL) can be performed in a number of different positions. Our aim was to evaluate the convenience and advantages of the supine position following the transition from the prone to the supine position. 94 patients undergoing supine PNL (Group-1) and 93 patients undergoing prone PNL (Group-2) were retrospectively reviewed and included in the study. Patients who underwent mini-PNL (mPNL) were selected from Group-1 and Group-2 and divided into Group-1A supine mPNL patients (77) and Group-2A prone mPNL patients (53). Demographic characteristics, operative data and post-operative parameters were compared between these groups. The operation time was 74.4 ± 21.9 min in Group-1A and 79.2 ± 19.8 min in Group-2A (p = 0.076). The median value of fluoroscopy time was 30 s in Group-1A and 40 s in Group-2A (p = 0.003). In Group-1A, 59 patients had no intraoperative double-J stent (DJS) insertion and 18 patients had DJS insertion, while in Group-2A, 24 patients had no DJS insertion and 29 patients had DJS insertion (p < 0.001). MPNL was performed in 81.9% of patients in the supine position and 57% in the prone position. This difference was statistically significant (p < 0.001). No significant difference was found with regard to the success rate and the complications of mPNL. Fluoroscopy time is shorter in the supine position. Moreover, the insertion rates of DJS are low. With increasing experience, we have found that our standard PNL (sPNL) rate is gradually decreasing and more mPNL is being performed.

Fluoroscopy screening time and radiation dose during complete supine percutaneous nephrolithotomy

PURPOSE

Fluoroscopy-guided percutaneous nephrolithotomy (PCNL) is procedure of choice for treatment of large urinary tract calculi. This study aimed to investigate the affecting factors on fluoroscopy screening time (FST) and radiation dose (RD) of patients undergoing complete supine percutaneous nephrolithotomy (csPCNL).

METHODS

Analytic cross-sectional study was performed on 355 patients who underwent csPCNL. The correlation between the FST and RD and patients' demographics, stone characteristics, preoperative, intraoperative and postoperative parameters were assessed. Multivariate regression analysis was used to explore various parameters which affect FST and RD.

RESULTS

Of all 355 patients, 191 (54.65%) were male and 161 were (45.35%) female with mean age of 48.29 ± 12.38 (16-82) years. BMI was 27.61 ± 4.53 (16.61-39.00) kg/m². The mean operative time was 45.87 ± 18.29 min with mean FST of 101.72 ± 62.00 s. BMI, operative time, success rate, complications, stone number, and tract number had a significant relationship with FST and RD (P < 0.05). On multivariate analysis, BMI, tract number and success rate were found to be independent predictors for FST and RD. Age, gender, operation side, GFR, target calyx, lithotripsy history, stone opacity, size and site, stone configuration and distribution, and hydronephrosis did not have any correlation with FST and RD (P > 0.05).

CONCLUSION

BMI, success rate and tract number can be significant predictor for FST and RD during csPCNL. Identifying the affecting factors on FST and RD can help the surgeon to minimize the danger of radiation exposure by predicting and preoperative planning.

Supine versus prone percutaneous nephrolithotomy for renal calculi: Our experience

Objectives:

To compare operative times, safety, and effectiveness of percutaneous nephrolithotomy in the supine versus the prone position.

Materials and methods:

An observational study of 100 patients was conducted in our institution for 2years from 2018 to 2020 divided into 2 groups: 50 patients underwent modified supine percutaneous nephrolithotomy (PCNL) and 50 patients underwent standard prone PCNL. The inclusion criteria included a renal calculus (calyx or pelvis) of any size for which PCNL was indicated and exclusion criteria were patients having contraindications for PCNL such as bleeding disorders, pregnancy, high risk, and co-morbid conditions. The measured data included operative time, number of punctures, stone-free rate, length of hospital stays, and rate of complications.

Results:

The 2 groups were comparable in mean age, male to female ratio, calculus size, number of punctures, residual calculi, and postoperative fever and pain. The mean difference of hemoglobin in the supine PCNL group was 0.37 g/dL whereas in the prone PCNL group it was 0.61 g/dL. The p value was significant at 0.043. The mean time to finish from initial postion was 72.24 minutes in supine PCNL and 88.12 minutes in prone PCNL. The p value was significant (p < 0.001). The mean time before puncture was 20.92 minutes in the supine position and 31.84 minutes in the prone position. The p value was significant (p < 0.001). The mean time from puncture to finish was 51.32 minutes in the supine position and 56.28 minutes in the prone position. The p value was significant (p < 0.001).

Conclusions:

As observed from this study, supine PCNL is associated with a significantly reduced operating time when compared to conventional prone position PCNL procedures. The postoperative complications such as pain and fever were not significantly different. Hence, the supine PCNL is an equally effective modality for treatment of a renal calculus with benefits of simultaneous retrograde access and less operative time compared to the prone PCNL.

Endoscopic combined intrarenal surgery in prone split-leg and inclined supine positions to treat renal cast and multiple calyx stones

This Invited Commentary discusses the following article:

Mulay A, Mane D, Mhaske S, Shah AS, Krishnappa D, Sabale V. Supine versus prone percutaneous nephrolithotomy for renal calculi: Our experience. Curr Urol 2022;16 (1):25-29. doi: 10.1097/CU9.0000000000000076.

A Percutaneous Nephrolithotripsy Performed in the Oblique Supine Lithotomy Position: A Better Choice

Objective. To investigate the efficacy and safety of the oblique supine lithotomy during percutaneous nephrolithotomy (PCNL) to treat upper urinary calculi. Methods. Clinical data were retrospectively analyzed for 371 patients with upper urinary calculi who underwent PCNL at The First Affiliated Hospital of Guangzhou University of Chinese Medicine from January 2017 to October 2020. Based on different positions, patients were divided into the observation group (oblique supine lithotomy position, 155 cases, Group 1) or control group (prone position, 216 cases, Group 2). Groups were compared for effectiveness, complications, bleeding, surgical time, clinical indicators, and hospitalization time. Results. There were no significant differences in the clinical baseline data between the two groups (p > .05). However, the stone-free rate for patients was significantly higher in the observation than in the control group (p < .05). Both operation time and hospital stay time were significantly lower in the observation versus the control groups (p < .05). No significant differences were observed for complications or amount of blood loss (p > .05). Conclusion. In patients with upper urinary calculi, percutaneous nephrolithotomy in the oblique supine lithotomy position has a higher stone-free rate than the prone position. This approach can shorten the operation and provide better comfort and quicker recovery to the patients. A further advantage is that there is no difference in safety and blood loss between the prone position and the oblique lithotomy position.

Is There a Role for Prone Computed Tomography Prior to Percutaneous Nephrolithotomy?

BACKGROUND

The majority of PCNLs are performed prone, while most pre-operative CT scans are done supine. The purpose of this pilot study is to determine if there is utility of prone CT scans in pre-operative planning for prone PCNL by identifying patient populations at risk for organ injury and tract length related complications.

MATERIALS AND METHODS

To represent typical pre-operative planning using CT, 2D-axial-prone/supine percutaneous tract measurements were performed by minimizing the distance from the target calyx to the posterior-lateral skin in a single axial plane. The minimum distance and organ interception rates for the 2D-axial planning scans were recorded.

RESULTS

A total of 60 CT Colonography and 13 CT Urography patients were included in analysis. There were 42 females and 31 males with unspecified pathologies ranging in age from 27 to 86 years and in BMI from 17.1 to 49. Multiple logistic regression identified female gender and low BMI as predictors of organ interception on the left. On multiple linear regression comparing the difference in axial prone/supine lengths; BMI, gender, and age were not significant independent predictors of changes in tract length in any pole when prone versus supine. However, shorter supine tracts tended to lengthen when prone, and longer supine tracts tended to shorten.

CONCLUSIONS

This pilot study has demonstrated that patients with very long and short estimates of tract length in the supine position may have shorter and longer tracts, respectively, with repositioning to prone. Thus, prone CT may have benefit when anticipating exceptionally long (>15cm) tract lengths. Prone scans also revealed more potential organ interceptions, particularly for low BMI and females in the left upper pole. In patients for whom prone CT demonstrates an organ interception, the urologist should consider an alternate target calyx or ultrasound guided percutaneous access to identify the most appropriate needle trajectory.

Prone versus Barts “flank-free” modified supine percutaneous nephrolithotomy: a match-pair analysis

Background/aim

In this study, we aimed to compare the results of prone and Barts “flank-free” modified supine percutaneous nephrolithotomy (PCNL) operations in our clinic.

Materials and methods

The data from patients that underwent Barts “flank-free” modified supine PCNL (BS-PCNL) (n = 52) between June 2018 and July 2020 and prone PCNL (P-PCNL) (n = 286) between April 2014 and June 2018 were retrospectively evaluated. Of those 286 patients, 104 patients whose sex, age, body mass index, American Society of Anesthesiology score, stone localization, stone size, and hydronephrosis matched the BS-PCNL group in a 1:2 ratio were included in the study. The groups were compared in terms of intraoperative outcome, complication rates, and stone-free rates.

Results

The mean age of all patients (58 females, 98 males) included in the study was 41.8 ± 15.2 years, and the mean body mass index (BMI) was 24.7 ± 2.9 kg/m2. The mean operation time was significantly shorter in the BS-PCNL group than in the P-PCNL group (80.2 ± 15.1 min vs. 92.4 ± 22.7 min and p = 0.01). There was no significant difference between the two groups in terms of fluoroscopy time, intraoperative complications, postoperative complications, and stone-free rates.

Conclusion

Our study shows that BS-PCNL is an effective and safe method that significantly reduces the operation time and should be considered as one of the primary treatment options for patients scheduled for PCNL.

Comparison of the Prone Split-Leg Position with the Traditional Prone Position in Percutaneous Nephrolithotomy: A Propensity Score-Matching Study

Background and Objective: Several positions have been described for percutaneous nephrolithotomy (PCNL). The aim of this study was to compare the safety and effectiveness of the traditional prone position PCNL (TP-PCNL) and the prone split-leg position PCNL (PSL-PCNL). Patients and Methods: A retrospective review was made of the data of 212 patients who underwent prone PCNL in PSL or TP between January 2017 and November 2019. The demographic and preoperative clinical data were used for propensity score-matching (PSM). Following the PSM based on a multivariable logistic regression model, the PSL-PCNL and TP-PCNL groups were compared in preoperative, perioperative, and postoperative parameters. All surgical procedures were performed by an experienced endourologist. Results: After PSM, 51 patients from the PSL-PCNL group were matched to 51 TP-PCNL patients. The stone burden was not statistically significant between the two groups (p = 0.388). The mean operation time of the two groups was significantly different (81.5 ± 32.4 minutes vs 93.1 ± 25.9 minutes, respectively, p = 0.026). The hemoglobin decrease in the PSL-PCNL group was greater than that in the TP-PCNL group (-17.7 ± 16.9 g/L vs 13.1 ± 10.9 g/L, p < 0.001). Both groups had similar stone-free rates after 2 weeks (p = 0.49). No significant difference was observed between the groups in the total complication rate (p = 1). Conclusions: The application of PSL in PCNL simplifies the surgical procedure and shortens the operating time. Another important advantage is that it allows retrograde intrarenal surgery and ureteroscopy to be performed simultaneously. We recommend the PSL to be applied in PCNL for renal stone patients.

Effects of horizontal versus vertical bolster alignment on anatomical orientation of kidney as applied to prone percutaneous nephrolithotomy

PURPOSE

To evaluate the anatomical changes in kidney orientation in prone position with use of horizontal or vertical bolster alignment.

METHODS

Patients having renal stone(s) on ultrasonogram or X-ray underwent split bolus computed-tomo-urography (CTU) in prone position with horizontal and vertical bolster positions. CTUs were read by a single radiologist to quantify the cranio-caudal, antero-posterior, side to side and rotational movements of kidneys as relevant to prone percutaneous nephrolithotomy.

RESULTS

19 adult patients with 38 renal units and mean basal metabolic index of 25.6 kg/m² underwent CTU. Greater inferior displacement of both kidneys was seen with horizontal bolsters as compared to vertical bolsters. The right upper calyceal-diaphragm distance was 2.1 ± 1.5 cm and the lower calyceal-diaphragm distance was 2.0 ± 1.6 cm greater with the horizontal bolsters (p < 0.01). Similarly, the displacement on the left side was 1.5 ± 0.8 cm and 1.4 ± 0.8 cm, respectively (p < 0.01). Horizontal bolsters also result in significantly longer calyceal-skin distance at both poles of both kidneys [right upper: 0.4 ± 0.5 cm (p < 0.01), right lower: 0.8 ± 0.7 cm (p < 0.01), left upper: 0.4 ± 0.6 cm (p = 0.02), left lower: 0.8 ± 1.1 cm (p < 0.01)] and wider erector spinae-mid posterior calyceal-colon angle (124.8 v/s 110.0 on the right and 96.2 v/s 85.7 on the left) (p < 0.01).

CONCLUSION

Horizontal bolsters provide significantly more caudal displacement of the kidneys; the right kidney being displaced more as compared to the left. However, there is also an increase in the skin-calyceal distance with horizontal as compared to the vertical bolsters. These assessments may help the surgeons decide optimal bolster position individualized to the patient.

Classification and standardized reporting of percutaneous nephrolithotomy (PCNL): International Alliance of Urolithiasis (IAU) Consensus Statements

BACKGROUND

The aim of this study was to reach a consensus in the classification and standardized reporting for the different types of PCNLs.

METHODS

The RAND/UCLA appropriateness methodology was used to reach a consensus. Thirty-two statements were formulated reviewing the literature on guidelines and consensus on PCNLs, and included procedure specific details, outcome measurements and a classification for PCNLs. Experts were invited to two rounds of input, the first enabled independent modifications of the proposed statements and provided the option to add statements. The second round facilitated scoring of all statements. Each statement was discussed in the third round to decide which statements to include. Any suggestion or disagreement was debated and discussed to reach a consensual agreement.

RESULTS

Twenty-five recommendations were identified to provide standardized reporting of procedure and outcomes. Consensual scoring above 80% were strongly agreed upon by the panel. The top treatment related outcomes were size of sheath used (99.1%) and position for PCNL (93.5%). The highest ranked Outcome Measures included definition of postoperative hospital length of stay (94.4%) and estimated blood loss (93.5%).

CONCLUSIONS

The consensus statements will be useful to clarify operative technique, in the design of clinical trials and standardized reporting, and presentation of results to compare outcomes of different types of PCNLs.

Management of upper calyceal stone by percutaneous nephrolithotomy through lower calyx access: prone versus supine position

Background

The best way in the management of calyceal stone by percutaneous nephrolithotomy (PCNL) is to go directly into the desired calyx. However, in upper calyx, this direct entry may be associated with undesired complications, and through lower calyx is limited in prone PCNL. Recently, there is another option about reaching it through the lower calyx in supine position with more accessibility and better manipulation. This study aimed to evaluate the management of the upper calyceal stone by PCNL through lower calyx access in prone versus supine position.

Methods

A total of 38 patients with upper calyceal stone (≥ 2 cm) were randomly divided into two groups; the first group included 18 patients managed by PCNL in the prone position, and the second group included 20 patients managed in supine position. All data of both procedures were collected and statistically analyzed to compare between both groups.

Results

There is no statistically significant difference between groups as regards demographic and stone characters. The angle between the access to the lower calyx and access of the upper calyx was significantly wider in the supine group versus prone group (130.2° ± 23.46° vs. 89.67° ± 14.56°, respectively). The mean operative and fluoroscopy time was significantly longer in the prone group. There is no significant difference in intraoperative or postoperative morbidity. The stone-free rate was significantly higher in the supine group than the prone group (85% vs 38.9%, respectively). Also stone approachability was higher in the supine group than prone group (95% vs. 66.7%, respectively).

Conclusion

Management of upper calyceal stone by PCNL through the lower calyx is safe, but it is more effective in the supine position than in prone position.

Comparison of supine and prone miniaturized percutaneous nephrolithotomy in the treatment of lower pole, middle pole and renal pelvic stones: A matched pair analysis

Purpose

We aimed to compare the outcomes of supine and prone miniaturized percutaneous nephrolithotomy (m-PNL) in the treatment of lower pole, middle pole and renal pelvic stones.

Materials and Methods

54 patients who performed supine m-PNL between January 2017 and March 2018 and 498 patients who performed prone m-PNL between April 2015 and January 2018 were included in the study. Of the 498 patients, 108 matching 1: 2 in terms of age, gender, body mass index, American Association of Anesthesiology score, stone size, stone localization and hydronephrosis according to the supine m-PNL group were selected as prone m-PNL group. The patients with solitary kidney, upper pole stone, urinary system anomaly or skeletal malformation and pediatric patients (<18 years old) were excluded from the study. The success was defined as ‘complete stone clearance’ and was determined according to the 1^st month computed tomography.

Results

The operation time and fluoroscopy time in supine m-PNL was significantly shorter than prone m-PNL group (58.1±45.9 vs. 80.1±40.0 min and 3.0±1.7 min vs. 4.9±4.5 min, p=0.025 and p=0.01, respectively). When post-operative complications were compared according to the modified Clavien-Dindo classification, overall and subgroup complication rates were comparable between groups. There was no significant difference between the groups in terms of the success rates (supine m-PNL; 72.2%, prone m-PNL; 71.3%, p=0.902).

Conclusions

Supine m-PNL procedure is more advantageous in terms of operation time and fluoroscopy time in the treatment of lower pole, middle pole and renal pelvic stones.

Invited review: the tale of ECIRS (Endoscopic Combined IntraRenal Surgery) in the Galdakao-modified supine Valdivia position

Modern-day percutaneous nephrolithotomy (PNL) has undergone considerable evolution, mainly driven by the improvement in access techniques, endoscopic instrumentation technology, lithotripsy devices and drainage management. The introduction of the supine and supine-modified positions is also part of this evolution, enabling comfortable and safe procedures from an anaesthesiological point of view, and an easy combined retrograde surgery [Endoscopic Combined IntraRenal Surgery (ECIRS)], allowing tailoring of the procedure on the patient, the dynamic anatomy of the collecting system and the urolithiasis. The conceptual value of ECIRS extends beyond the single diagnostic and active advantages due to the simultaneous contribution of the flexible retrograde ureteroscopy: the merit consists in the promotion of the versatile attitude of the urologist, and in the fulfillment of a personalized stone management. ECIRS has no pretensions of superiority, but for sure is a new safe and effective way of interpreting PNL, in the hands of an experienced surgical team.