Supine vs. Prone Mini-PCNL in Children

Introduction

Pediatric urinary stones could be managed effectively using minimally invasive treatment modalities such as extracorporeal shock wave lithotripsy (ESWL), retrograde intrarenal surgery (RIRS), and percutaneous nephrolithotomy (PCNL). But PCNL had a significant role in cases with large and/or ESWL resistant stones. The European Association of Urology guidelines recommended PCNL as the primary treatment option for large renal stones (> 20 mm) and also for > 10 mm stones in the lower renal pole (Ozden E et al., 2016).

Percutaneous nephrolithotomy (PCNL) is the gold procedure for large stones and complex kidney disorder treatment, but its morbidity was the highest between different stone treatments. For minimizing complication rates, surgeons must develop different variations of the classic prone position where PCNL is usually performed; one of them is the supine position (Mourmouris P et al., 2018). PCNL mostly performed in the prone position, but the supine position has proven to be a better option with several advantages. PCNL in the supine position has a similar success rate and a shorter operative time than conventional PCNL (Desoky E et al., 2018).

Supine PCNL enables a single positioning through the operation, with easy patient ventilation and protection from positional injuries, with convenient access to the patient by the anesthesiologist, and also improves the ergonomic environment for the surgical urologist (who may be seated while operating) and easy endoscopic combined intrarenal surgery (ECIRS) if needed (Sofer M et al., 2017).

The advantages of the supine position lead to considering supine PCNL the gold standard for urologists worldwide, and it is still considered a new, not an alternative, position (Valdivia-Urìa J et al., 2011).

Aim of the Study

This study aims to compare safety \& outcomes, such as operative time, complication rates, and stone-free rates in the prone position versus the supine position in mini-percutaneous nephrolithotripsy (Mini-PCNL) in children less than 15 years old for renal stones less than 3 cm.

Patients and methods

This study will include 50 patients with renal stones less than 3 cm scheduled for PCNL admitted to the Urology Department, Fayoum University. The patients will be prospectively randomized into two groups (with a ratio of 1:1, 25 patients per group).

* Group A for mini percutaneous nephrolithotripsy in the supine position.
* Group B for mini percutaneous nephrolithotripsy in the prone position.

Inclusion criteria

1. Patients diagnosed with single renal pelvis stones or middle or lower calyceal stones.
2. Stone size ranged from 10 mm up to 30 mm.
3. Children less than 15 years old, both sexes.

Exclusion criteria:

1. Patients with renal anomalies such as horseshoe kidney, ectopic pelvic kidney, crossed fused renal ectopia, UPJ obstruction, or ureteric stricture.
2. Patients with staghorn stones or upper calyceal stones.
3. Patients with active urinary tract infection.
4. Patients with bleeding disorders.

Sample Size

The sample size was calculated using G*Power software version 3.1.9.7. Based on data reported by Abdel Ghani et al. (2024), the mean operative time was 65.2 ± 9.6 minutes in the supine Mini-PCNL group and 82.6 ± 10 minutes in the prone Mini-PCNL group. Using a two-tailed independent samples t-test, an alpha error of 0.05, and a study power of 80%, the minimum required sample size was a total of 28 participants, which is equivalent to 14 patients per group. To account for potential dropouts and improve statistical validity, a total of 50 participants (25 per group) will be enrolled.

Preoperative assessment

All patients will be evaluated with a full medical \& surgical history and a general \& abdominal and local examination focusing on:

* Upper urinary tract symptoms.
* Previous surgical procedures (open or endoscopy ).

Laboratory Investigations

* Urine analysis, culture, and sensitivity.
* Complete blood count (CBC) .
* Coagulation profile (I.N.R, PT, PTT).
* Kidney function tests: blood urea and serum creatinine.
* Liver functions test; ALT, AST, ALP, albumin, and bilirubin.

Radiological Examination

* Pelvic-abdominal ultrasound.
* Kidney-ureters-bladder X-ray (KUB) .
* Non Contrast Spiral Computed Tomography (NCSCT) for :

* Measuring stone size, site, distribution, and HU.
* Pelvi-calyceal anatomy .
* Relation of the kidney to the related organs.

Operative technique Patients will be given prophylactic intravenous antibiotics (cefoperazone50-100mg/kg) were administered 1 hours preoperatively.

Positioning: In the two groups:

Cystoscopy will be performed in the lithotomy position by pediatric cystoscopy, the ureteral orifice will be identified and a 0.025 inch guide wire will be introduced; the wire will be advanced under fluoroscopic guidance to the level of pelvicalyceal system, 5F or 6F open-ended ureteral catheter will be advanced over the wire and the guide wire will be removed, leaving the ureteral catheter in place, a retrograde ureteropyelography will be done, and a ureteral catheter will be fixed with tape to an appropriate Foley's catheter.

In Group A: Patients were kept in Supine position using a suitable cushion (water bag) under the ipsilateral shoulder, fixing the ipsilateral arm over the thorax, then crossing the extended patient ipsilateral leg over the contralateral leg, all pressure points were checked carefully and padded.

In Group B: Patients were placed in the Prone position, and all pressure points are checked carefully and padded. A pillow was placed under the chest and another pillow was placed under the symphysis as a support to allow optimal ventilation.

Technical aspect (in both groups):

A preplanned tract or tracts are designed along the maximum stone burden so that these tracts are punctured and safety wires are inserted before dilatation, The skin will be punctured posteriorly to the posterior axillary line by 18G puncture needle and, the track will be dilated sequentially using fascial dilators and a 16Fr amplatz sheath will be advanced over its metal dilator under fluoroscopic, 16Fr amplatz sheath will be positioned, allowing the introduction of 8.5 to 11Fr semi-rigid ureteroscope.

The warmed Saline 0.9% will be used for irrigation at a suitable height from the level of the operating table, Stones will be fragmented using power (1.6-1.8 joule) and frequency (8-10 hertz) Ho:YAG laser with a 550-μm fiber laser lithotriptor and large fragments will be retrieved by grasper and stone are dusting using low power ( 0.8-1.0 joule) and high frequency(15-20 hertz) Ho:YAG laser and by The popcorn' technique for the small one.

Nephrostomy catheter 14Fr will be inserted at the end of the procedure under fluoroscopic guidance, the nephrostomy is secured at the skin with a silk suture, and the wound is dressed, The appropriate Antigrade double-J stent will be routinely maintained in place following the procedure.

Intraoperative Data In the operation record, the operative time; calculated from the beginning of ureteral catheterization to the nephrostomy tube placement, the position time from the end of ureteral catheter insertion to the beginning of puncture, access time defined as the time from the beginning of puncturing of the skin to establish the tract, fluoroscopy time defined as time was patient exposed to radiation .and LASER time as defined the time use LASER to fragments and dusting stone. Any requirements for blood transfusion, any complications within the operation or number of punctures will be recorded.

Postoperative Period \& Follow-up All patients will be observed in the recovery room for 30-60 minutes. Nephrostomy tube will be clamped in the first 2h post-operatively then opened till 24h post-operative day and will be removed in the second post-operative day if there is no indication for a second look or any signs of early infection.

Post-operative complete blood count (CBC), serum creatinine (S.cr) and C- reactive protein (CRP) tests will be done for all patients in first 24h. KUB will be done in the 2nd post-operative day for evaluation of the radiopaque residual fragments, and position of the double-J stent in addition to non contrast spiral Computer tomography (NCSCT) will be done post-operatively for measuring of radiolucent residual fragments.

The patients would be considered free of stones if there were no detected residual fragments less than 4mm in largest dimension (Zhong F, Alberto G et al., 2018). For residual fragments measuring 4-10 mm will be referred for ESWL after 2 weeks, and for residual fragments more than 10mm 2nd look PCNL will be planned after 1 week post-operatively.

Urethral catheter will be removed after 48h post-operatively and double-J stent will be removed after one month. Post-operative antibiotics (cefoperazone 50-100mg/kg) will be routinely continued twice daily for 5days.

Urine analysis and urine culture \& sensitivity will be done for all patients after 2 weeks post-operatively.

All patients will be observed for 2 weeks post-operatively for any Complications such as hematuria, any signs of infection, urinary leakage, renal colic, and symptoms of peritonitis.

Statistical analysis

Analysis of data was carried out using the statistical package of social science (SPSS version 20). Description of quantitative variables was given as mean, and standard deviation. Chi square test ( χ2 -test) was used to compare qualitative variables between groups. The t-test was used to compare quantitative variables in parametric data. The Z-test was used for proportions. P-values less than 0.05 will be considered significant and P values less than 0.01 were considered highly significant.

Ethical Consideration:

All the individuals and their familes included in the study will be informed about the procedures regarding the study and will be informed of their rights to refuse participation or withdraw from the study without having to give reasons. Participants were guaranteed anonymity and all information provided would be treated with confidentiality.

The required administrative regulations will be fulfilled according to the ethical approval of the Faculty of Medicine, Fayoum University Scientific Research Ethics Committee.

• Group A (Procedure), also known as Supine Mini-PCNL: Mini-PCNL (16Fr Amplatz sheath, 8.5-11Fr ureteroscope, Ho:YAG laser) performed in the supine position using a cushion under the ipsilateral shoulder.
• Group B (Procedure), also known as Prone Mini-PCNL: Mini-PCNL (16Fr Amplatz sheath, 8.5-11Fr ureteroscope, Ho:YAG laser) performed in the conventional prone position with chest and symphysis support.

Primary outcomes

• Operative Time [Intraoperatively (from initial skin incision to final skin closure)]: Total duration of the surgical procedure measured in minutes.
• Stone-Free Rate (SFR) [1 month post-surgery]: Percentage of patients with complete absence of stones or residual fragments < 4 mm, assessed via non-contrast CT or KUB X-ray.

Secondary outcomes

• Complication Rate [Intraoperatively through 30 days post-surgery]: Rate and severity of complications classified via the modified Clavien-Dindo system.
• Positioning Time [Intraoperatively (from completion of ureteral catheter insertion to initial skin puncture)]: Duration required to position and pad the patient in either the supine or prone position.

Other outcomes

• Access Time [Intraoperatively (from initial skin puncture to Amplatz sheath positioning)]: Time required to establish renal tract access under fluoroscopic guidance.
• Fluoroscopy Radiation Time [Intraoperatively (during surgical procedure)]: Total intraoperative radiation exposure time during the procedure.
• Laser Lithotripsy Time [Intraoperatively (from start to end of laser energy delivery)]: Active duration of laser usage for stone fragmentation and dusting.
• Length of Hospital Stay [From date of surgery through hospital discharge (an average of 2 to 3 days)]: Total postoperative duration of hospitalization prior to discharge.

Sex: All, ages: 6 Months to 15 Years

Inclusion Criteria:

* Children under 15 years old (both sexes).
* Diagnosed with a single renal pelvis stone, or middle/lower calyceal stone.
* Stone size ranging from 10 mm up to 30 mm (measured via non-contrast CT).

Exclusion Criteria:

* Congenital renal anomalies (e.g., horseshoe kidney, ectopic pelvic kidney, crossed fused ectopia, UPJ obstruction, or ureteric stricture).
* Staghorn stones or upper calyceal stones.
* Active urinary tract infection (UTI).
* Bleeding disorders or uncorrected coagulopathy.