Extracorporeal shock wave lithotripsy for treatment of large pediatric renal pelvic stone burden more than 2 cm.

BACKGROUND: The high recurrence rates in pediatric urolithiasis indicate the need for none invasive or a minimally invasive treatment such as SWL. Therefore, EAU, ESPU and AUA recommend SWL as a first line treatment for renal calculi ≤ 2, and RIRS or PCNL for renal calculi > 2 cm. SWL is superior to RIRS and PCNL as it is inexpensive, outpatient procedure, and it has a high SFR in well selected cases specially pediatrics. On the other hand, SWL therapy has a limited efficacy with a lower SFR, and high retreatment rate and/or additional interventions for treatment of larger and harder renal calculi.

OBJECTIVE: We carried out this study to evaluate the efficacy and safety of SWL for treatment of renal stones > 2 cm to extend its indications for pediatric renal calculi.

METHODS: Between January 2016 and April 2022, we reviewed the records of patients with renal calculi treated by SWL, mini-PCNL, RIRS and open surgery in our institution. Forty-nine eligible children aged 1-5 years old, presented with renal pelvic and/or calyceal calculi measuring 2-3.9 cm and underwent SWL therapy were picked up and participated in the study. The data of an additional eligible 79 children with the same age and had renal pelvic and/or calyceal calculi > 2 cm up to stag horn calculi and underwent mini-PCNL, RIRS and open renal surgery were also picked up and participated in the study. We retrieved the following preoperative data from the records of the eligible patients; age, gender, weight, length, radiological findings (stone size, side, site, number and radio-density), renal function tests, routine laboratory findings, and urine analysis. The outcomes data in the form of; operative time, fluoroscopy time, hospital stay, SFRs, retreatment rates and complication rates were also retrieved from the records of patients treated with SWL and other techniques. Also, we collected the SWL characteristics in terms of; position, number and frequency of shocks, voltage, time of the session and U/S monitoring to assess stone fragmentation. All SWL procedures were performed according to the institution's standards.

RESULTS: The mean age of patients treated with SWL was 3.23 ± 1.19 years old, the mean size of the treated calculi was 2.31 ± 0.49 and the mean length of the SSD was 8.2 ± 1.4 cm. All patients had NCCT scan and the mean radio-density of the treated calculi was 572 ± 169.08 HUs based on NCCT scans Table (1). Single- and two-session SFRs of SWL therapy were 75.5% (37/49 patients) and 93.9% (46/49 patients), respectively. The overall success rate was 95.9% (47/49 patients) after three-session of SWL. Complications experienced by 7 patients (14.3%) in the form of fever (4.1%), vomiting (4.1%), abdominal pain (4/1%), and hematuria (2%). All complications were managed in outpatient settings. Our results were obtained on the basis of preoperative NCCT scans for all patients and postoperative plain KUB films and real-time abdominal U/S. Furthermore, single-session SFRs for SWL, mini-PCNL, RIRS and open surgery were 75.5%, 82.1%, 73.7% and 90.6%, respectively. Two-session SFRs by the same technique were 93.9%, 92.8%, and 89.5% for SWL, mini-PCNL and RIRS, respectively. A lower overall complication rate and higher overall SFR were found with SWL therapy compared to other techniques, Fig. (1).

DISCUSSION: Being a non-invasive outpatient procedure with a low complication rate and good spontaneous passage of stone fragments is the main advantage of SWL. In this study, the overall SFR is 93.9% where 46 out of 49 patients were completely rendered stone free after three session of SWL with overall success rate 95.9%. Badawy et al. reported overall success rates of 83.4% for renal stones with a mean stone size of 12.5 ± 7.2 mm. In children with renal stones measuring 18.2 mm, Ramakrishnan et al. reported a 97% SFR in accordance with our results. The high overall success rate (95.9%) and SFR (93.9%) in our research were attributed to the regular use of ramping procedure, low shock wave rate, percussion diuretics inversion (PDI) approach and alpha blocker therapy in all participants and short SSD. The limitations of our study are small sample of patients and its retrospective nature.

CONCLUSION: The non-invasive nature and replicability of the SWL procedure, along with the high success and low complication rates, give us a new insight to consider its application for treating pediatric renal calculi > 2 cm over the other more invasive techniques. Short SSD, the use of ramping procedure, low shock wave rate, 2 min break, PDI approach and alpha blockers therapy help better success of SWL.

LEVEL OF EVIDENCE: IV.