A Study of Percutaneous Nephrolithotomy (PCNL) & Grading the Complexity of PCNL using Modified Guys Stone Score

Abstract

Introduction: Renal stone disease is a common urological condition, and percutaneous nephrolithotomy (PCNL) is widely used for the management of large and complex renal calculi.

Aim & Objective: The present study aimed to evaluate patients undergoing PCNL, assess procedural outcomes, and determine usefulness of the Modified Guy’s Stone Score (MGSS) in grading stone complexity and predicting stone-free status and postoperative complications.

Material & Methods: This prospective observational study included 50 patients with renal stones who underwent PCNL. Patients were evaluated clinically and radiologically, stone characteristics were assessed using the MGSS. Operative time, hospital stay, residual stones, stone-free rate (SFR), complications, ancillary procedures, postoperative complications according to the Modified Clavien classification were recorded. Statistical analysis was performed using SPSS version 25.0, with p<0.05 considered statistically significant.

Results: The study included 25 males and 25 females, with a mean age of 42.48±12.51 years. Mean stone burden was 2.88±0.49 cm. Grade 1 was the most frequent MGSS category (58%). Overall, 40 (80%) patients achieved stone-free status, while 10 (20%) had residual stones. SFR progressively decreased with increasing MGSS, from 96.6% in Grade 1 to 0% in Grade 4b. MGSS was significantly associated with operative time (p=0.001), stone burden (p=0.001), hospital stay (p=0.006), residual stones (p=0.01), and ancillary procedures (p=0.007). Complications occurred in 48% of patients, predominantly fever and bleeding. The mean operative time was 88.40±19.42 minutes and mean hospital stay was 7.60±2.12 days.

Conclusion: MGSS effectively stratified PCNL complexity and demonstrated a significant association with stone-free rate, operative time, hospital stay, residual stones, ancillary procedures, postoperative complications. Higher MGSS grades were associated with poorer stone clearance and greater procedural complexity. Therefore, MGSS is a useful preoperative tool for surgical planning, risk stratification, patient counseling, and prediction of PCNL outcomes.

REFERENCES

1. Lang J, Narendrula A, El-Zawahry A, Sindhwani P, Ekwenna O. Global trends in incidence and burden of urolithiasis from 1990 to 2019: an analysis of Global Burden of Disease Study data. Eur Urol Open Sci. 2022;35:37-46. https://doi.org/10.1016/j.euros.2021.10.008
2. Jiao B, Ding Z, Luo Z, Lai S, Xu X, Chen X, et al. Single-versus multiple-tract percutaneous nephrolithotomy in the surgical management of staghorn stones or complex caliceal calculi: a systematic review and meta-analysis. Biomed Res Int. 2020;2020:1-11. https://doi.org/10.1155/2020/8817070
3. Chen J, Zhou X, Chen Z, Liu L, Jiang L, Chen C, et al. Multiple tracts percutaneous nephrolithotomy assisted by LithoClast master in one session for staghorn calculi: report of 117 cases. Urolithiasis. 2014;42(2):165-169. https://doi.org/10.1007/s00240-013-0632-1
4. Thomas K, Smith NC, Hegarty N, Glass JM. The Guy's stone score-grading the complexity of percutaneous nephrolithotomy procedures. Urology. 2011;78(2):277-281. https://doi.org/10.1016/j.urology.2010.12.026
5. Naeem Z, Tabasum P, Mustajab M, Abid A, Khawaja MA, Ramzan H, et al. Percutaneous nephrolithotomy versus retrograde intrarenal surgery: a systematic review and meta-analysis of stone-free rates and complication profiles. Int Urol Nephrol. 2026;58(2):407-431. https://doi.org/10.1007/s11255-025-04707-8
6. Biswas K, Gupta SK, Tak GR, Ganpule AP, Sabnis RB, Desai MR. Comparison of STONE score, Guy's stone score and Clinical Research Office of the Endourological Society (CROES) score as predictive tools for percutaneous nephrolithotomy outcome: a prospective study. BJU Int. 2020;126(4):494-501. https://doi.org/10.1111/bju.15130
7. Shahab S, Galeti EH, Bharali MD. Comparative study between Guy's stone score, STONE nephrolithometry and Clinical Research Office of the Endourological Society (CROES) nephrolithometric nomogram in predicting stone-free rates in patients undergoing percutaneous nephrolithotomy: a prospective analysis. J Dr YSR Univ Health Sci. 2022;11(4):336-343. https://doi.org/10.4103/jdrntruhs.jdrntruhs_42_22
8. Hébert M, Cartier R, Dagenais F, Langlois Y, Coutu M, Noiseux N, et al. Standardizing postoperative complications-validating the Clavien-Dindo complications classification in cardiac surgery. Semin Thorac Cardiovasc Surg. 2021;33(2):443-451. https://doi.org/10.1053/j.semtcvs.2020.09.029
9. Kumar U, Tomar V, Yadav SS, Priyadarshi S, Vyas N, Agarwal N, et al. STONE score versus Guy's stone score-prospective comparative evaluation for success rate and complications in percutaneous nephrolithotomy. Urol Ann. 2018;10(1):76-81. https://doi.org/10.4103/ua.ua_119_17
10. Kadlec AO, Greco KA, Fridirici ZC, Hart ST, Vellos TG, Turk TM. Comparison of complication rates for unilateral and bilateral percutaneous nephrolithotomy (PCNL) using a modified Clavien grading system. BJU Int. 2013;111(4):243-248. https://doi.org/10.1111/j.1464-410x.2012.11589.x
11. Withington J, Armitage J, Finch W, Wiseman O, Glass J, Burgess N. Assessment of stone complexity for PCNL: a systematic review of the literature, how best can we record stone complexity in PCNL? J Endourol. 2016;30(1):13-23. https://doi.org/10.1089/end.2015.0278
12. Ihedoro IE, Ngwu PE, Obodozie CH, Ohiarah CP, Onyemachi EV. Use of the STONE score for predicting the outcomes of lithotripsy: a narrative review. Cureus. 2025;17(8):1-11. https://doi.org/10.7759/cureus.90570
13. Mandal S, Goel A, Kathpalia R, Sankhwar S, Singh V, Sinha RJ, et al. Prospective evaluation of complications using the modified Clavien grading system, and of success rates of percutaneous nephrolithotomy using Guy's stone score: a single-center experience. Indian J Urol. 2012;28(4):392-398. https://doi.org/10.4103/0970-1591.105749
14. Moudi E, Hosseini SR, Bijani A. Nephrolithiasis in elderly population: effect of demographic characteristics. J Nephropathol. 2017;6(2):63-68. https://doi.org/10.15171/jnp.2017.11
15. Tekgül S, Stein R, Bogaert G, Nijman RJ, Quaedackers J, Hoen LT, et al. European Association of Urology and European Society for Paediatric Urology guidelines on paediatric urinary stone disease. Eur Urol Focus. 2022;8(3):833-839. https://doi.org/10.1016/j.euf.2021.05.006
16. Gade AC, Shinde SS, Tarle SB, Adhari AM, Badole PC, Qureshi A. Chronic discharging sinus following percutaneous nephrolithotomy: a study of 100 postoperative cases. SSR Inst Int J Life Sci. 2026;12(1):9242-9250. https://doi.org/10.21276/ssr-iijls.2026.12.1.39
17. Desai M, De Lisa A, Turna B, Rioja J, Walfridsson H, D'Addessi A, et al. The Clinical Research Office of the Endourological Society percutaneous nephrolithotomy global study: staghorn versus nonstaghorn stones. J Endourol. 2011;25(8):1263-1268. https://doi.org/10.1590/s1677-55382011000500016
18. Alnadhari I, Abdeljaleel O, Ali O, Shamsodini A, Al-Ansari A, Salah M. Comparison between flexible and navigable suction ureteral access sheath and standard ureteral access sheath during flexible ureteroscopy for the management of kidney stone: systematic review and meta-analysis. BMC Urol. 2025;25(1):1-14. https://doi.org/10.1186/s12894-025-01799-3
19. Agarwal MM, Singh SK, Mavuduru R, Mandal AK. Preventive fluid and dietary therapy for urolithiasis: an appraisal of strength, controversies and lacunae of current literature. Indian J Urol. 2011;27(3):310-319. https://doi.org/10.4103/0970-1591.85423
20. De la Rosette J, Assimos D, Desai M, Gutierrez J, Lingeman J, Scarpa R, et al. The Clinical Research Office of the Endourological Society percutaneous nephrolithotomy global study: indications, complications, and outcomes in 5803 patients. J Endourol. 2011;25(1):11-17. https://doi.org/10.1089/end.2010.0424
21. Yuhico MP, Ko R. The current status of percutaneous nephrolithotomy in the management of kidney stones. Minerva Urol Nefrol. 2008;60(3):159-175.
22. Mazzon G, Choong S, Celia A. Stone-scoring systems for predicting complications in percutaneous nephrolithotomy: a systematic review of the literature. Asian J Urol. 2023;10(3):226-238. https://doi.org/10.1016/j.ajur.2023.01.005
23. De la Rosette JJ, Opondo D, Daels FP, Giusti G, Serrano Á, Kandasami SV, et al. Categorisation of complications and validation of the Clavien score for percutaneous nephrolithotomy. Eur Urol. 2012;62(2):246-255. https://doi.org/10.1016/j.eururo.2012.03.055
24. Silva ML, Sanguinetti H, Tagliapietra LP, Aguilar J, Bernardo N. Is Guy's stone score useful for predicting outcomes in percutaneous nephrolithotomy? Actas Urol Esp (Engl Ed). 2022;46(2):92-97. https://doi.org/10.1016/j.acuroe.2021.01.009
25. Adapala RK, Prabhu GL, Shetty R, Yalla DR, Rakesh B, Venugopal P. Role of preoperative renal stone complexity assessment by Guy's stone score as a predictor of percutaneous nephrolithotomy outcomes. Urol Int. 2021;105(8):548-553. https://doi.org/10.1159/000505979