The most commonly used scoring systems include the Clinical Research Office of the Endourological Society (CROES) score, Guy's stone score (GSS), and the S.T.O.N.E. scoring system, which considers stone size, tract length, obstruction, the number of involved calyces, and essence/stone density. While these nomograms have undergone extensive evaluation and some validation in pediatric populations, they were initially created for adults.1-3 The Stone-Kidney Size (SKS) scoring system is particularly significant as it is the first nomogram specifically designed for pediatric patients.4 The SKS scoring system evaluates two variables and categorizes patients into three risk levels. Its use of fewer parameters compared to other scoring systems highlights its practical simplicity. This study is the first to externally assess the correlation between the SKS scoring system and stone-free status, as well as complications following pediatric PCNL.
In the literature, the stone-free rate (SFR) following PCNL in pediatric patients varies widely between studies, depending on the cutoff values and study populations. Our findings demonstrated a statistically significant association between the SKS score and SFR, consistent with the original study by Citamak et al., which introduced the scoring system.4 Additionally, the criteria for defining success are crucial. In our research, we conducted two analyses: one using only SFR patients and another including both SFR and clinically insignificant residual fragment patients. This approach allowed us to demonstrate the effectiveness of the SKS score, not only in cases with complete stone clearance but also when using a 4 mm cutoff.
Complications following PCNL in pediatric patients are reported to be mostly minor, with major complications being quite rare.5 However, unlike the study by Citamak et al., we did not find a statistically significant relationship between the SKS score and complications.4 We hypothesize that the SKS score may not effectively predict complications because it does not account for factors such as the degree of hydronephrosis, the number of tracts, operation time, preoperative positive urine culture, and tract size, which could be associated with complications.2,6 Additionally, the SKS score may not adequately assess stone characteristics, such as staghorn formation, which could also contribute to complications.
The most significant limitation of our study is that non-contrast computed tomography imaging was not available for all patients, so ultrasonography was used instead. While this may introduce variability among the patients in our study cohort, we believe it was necessary to minimize radiation exposure, given our focus on a pediatric population. Therefore, the results of this study need to be confirmed in prospective studies where a single imaging method is consistently used.
Written by: Hakan Bahadir Haberal, MD FEBU, Department of Urology, Ankara Ataturk Sanatoryum Training and Research Hospital, Ministry of Health, University of Health Sciences, Ankara, Turkey
References:
- Aldaqadossi HA, Khairy Salem H, Kotb Y, Hussein HA, Shaker H, Dikaios N (2017) Prediction of Pediatric Percutaneous Nephrolithotomy Outcomes Using Contemporary Scoring Systems. J Urol 198(5):1146-52.
- Caglayan V, Onen E, Avci S, Sambel M, Kilic M, Oner S (2019) Comparison of Guy's Stone Score and clinical research of the endourological society nomogram for predicting surgical outcomes after pediatric percutaneous nephrolithotomy: a single center study. Minerva Urol Nefrol 71(6):619-26.
- Utangac MM, Tepeler A, Daggulli M, Tosun M, Dede O, Armagan A (2016) Comparison of Scoring Systems in Pediatric Mini-Percutaneous Nephrolithotomy. Urology 93(40-4.
- Citamak B, Dogan HS, Ceylan T, Hazir B, Bilen CY, Sahin A, Tekgul S (2019) A new simple scoring system for prediction of success and complication rates in pediatric percutaneous nephrolithotomy: stone-kidney size score. J Pediatr Urol 15(1):67 e1- e6.
- Ozden E, Mercimek MN (2016) Percutaneous nephrolithotomy in pediatric age group: Assessment of effectiveness and complications. World J Nephrol 5(1):84-9.
- Onal B, Dogan HS, Satar N, Bilen CY, Gunes A, Ozden E, Ozturk A, Demirci D, Istanbulluoglu O, Gurocak S, Nazli O, Tanriverdi O, Kefi A, Korgali E, Silay MS, Inci K, Izol V, Altintas R, Kilicarslan H, Sarikaya S, Yalcin V, Aygun C, Gevher F, Aridogan IA, Tekgul S (2014) Factors affecting complication rates of percutaneous nephrolithotomy in children: results of a multi-institutional retrospective analysis by the Turkish pediatric urology society. J Urol 191(3):777-82.