Renal stone disease continues to represent a major urological health burden worldwide, with a rising incidence linked to changing dietary patterns, metabolic abnormalities, and sedentary lifestyles [1]. Management of large, multiple, and anatomically complex renal calculi often necessitates surgical intervention, and percutaneous nephrolithotomy (PCNL) has emerged as the treatment of choice for such cases. Despite advances in instrumentation and surgical techniques that have improved stone clearance rates, PCNL remains associated with procedure-related morbidity, particularly in patients with complex stone anatomy [2]. Preoperative assessment of stone burden and complexity plays a pivotal role in predicting operative difficulty, surgical outcomes, and the risk of complications. To standardize this assessment, several nephrolithometric scoring systems have been developed, including the Guy’s stone score (GSS), S.T.O.N.E. nephrolithometry score, and the Clinical Research Office of the Endourological Society (CROES) nomogram [3,4]. Among these, Guy’s stone score is widely adopted due to its simplicity, ease of application, and reliance on routinely available radiological imaging. It stratifies renal stones into four grades based on stone number, location, and associated anatomical abnormalities, providing an objective estimation of procedural complexity [3]. Multiple studies have validated the clinical relevance of Guy’s stone score, demonstrating a significant association between higher grades and increased operative time, reduced stone-free rates, higher complication rates, and prolonged hospital stay [1,4,5]. Comparative analyses have also shown that Guy’s stone score performs favorably alongside other scoring systems in predicting PCNL outcomes, reinforcing its utility in routine clinical practice [2,6]. However, variations in patient demographics, stone characteristics, and institutional practices necessitate continued evaluation of this scoring system across different settings. The present study was therefore undertaken to assess the effectiveness of Guy’s stone score in grading PCNL procedural complexity and to analyze its relationship with operative outcomes, stone-free rates, postoperative complications, and the need for ancillary procedures in a tertiary care center.

Study Design and Setting This prospective observational study was conducted in the Department of Urology at Guntur Medical College, Guntur, Andhra Pradesh, over a period of 18 months from July 2021 to December 2022. The study was undertaken after obtaining approval from the Institutional Ethics Committee, and written informed consent was obtained from all participants prior to enrollment. Study Population A total of 50 patients with symptomatic renal calculi who underwent percutaneous nephrolithotomy (PCNL) during the study period were included. Inclusion criteria comprised patients diagnosed with renal calculi and planned for PCNL. Exclusion criteria included patients unfit for surgery due to bleeding diathesis, high cardiac risk, active infection, or sepsis. Preoperative Evaluation All patients underwent a comprehensive preoperative assessment, including renal function tests, urine culture, X-ray kidney–ureter–bladder (KUB), ultrasonography of the abdomen, intravenous urography (IVU), and computed tomography (CT) urogram when indicated. Stone burden was defined as the maximum diameter of the stone measured on X-ray KUB or CT urogram. Stone complexity was classified preoperatively using Guy’s stone score (Grades I–IV) based on radiological findings. Surgical Technique PCNL was performed under general anesthesia using a standard prone technique. Initially, a 5F ureteric catheter was placed cystoscopically in a retrograde fashion, allowing instillation of saline or contrast. A 16F Foley catheter was then inserted. Patients were repositioned prone, and renal access was obtained under fluoroscopic guidance using an 18-gauge puncture needle. A 0.035-inch Terumo guidewire was introduced into the collecting system. Following a 10 mm skin incision, tract dilation was achieved using serial Amplatz dilators ranging from 8F to 22F, after which a 24F Amplatz sheath was placed. In selected cases, a single reusable 22F Amplatz dilator was used after initial dilation. A nephroscope was introduced through the sheath, and stone fragmentation was performed using a pneumatic lithoclast. Stone fragments were retrieved using grasping forceps or irrigation pressure. Complete stone clearance was confirmed fluoroscopically. At the end of the procedure, a double-J ureteral stent and an 18F percutaneous nephrostomy tube were placed. The nephrostomy tube and Foley catheter were removed on postoperative day 2, and the DJ stent was removed after two weeks. Outcome Measures Demographic details, intraoperative findings, operative time, and hospital stay were recorded. Hemoglobin levels were assessed preoperatively and postoperatively. Bleeding was considered a complication if it necessitated blood transfusion or led to termination of the procedure. Postoperative complications, including fever, transient rise in serum creatinine, sepsis, organ injury, and mortality, were documented and graded according to the modified Clavien–Dindo classification. Residual stones larger than 4 mm requiring ancillary procedures were considered clinically significant. Statistical Analysis Data were analyzed to assess the relationship between Guy’s stone score and operative outcomes, stone-free rates, complications, and need for ancillary procedures. Statistical significance was defined as a p-value < 0.05.

A total of 50 patients underwent percutaneous nephrolithotomy (PCNL) during the study period. The study population had a mean age of 42.62 ± 12.06 years, with ages ranging from 18 to 70 years. The 41–50-year age group constituted the largest proportion of patients. There was an almost equal gender distribution, with 26 males and 24 females. The mean stone burden was 2.88 ± 0.49 cm. The average duration of hospital stay was 7.46 ± 1.92 days, and the overall mean operating time was 88.40 ± 19.42 minutes (Table 1). Table 1. Demographic and Baseline Clinical Characteristics (N = 50) Variable Value Age (years), mean ± SD 42.62 ± 12.06 Age range (years) 18 – 70 Most common age group 41–50 years Male : Female 26 : 24 Stone burden (cm), mean ± SD 2.88 ± 0.49 Hospital stay (days), mean ± SD 7.46 ± 1.92 Operating time (minutes), mean ± SD 88.40 ± 19.42 According to Guy’s stone score, the majority of patients were classified as Grade I (64%), followed by Grade II (18%), Grade III (12%), and Grade IV (6%). Grade I stones were predominantly solitary pelvic, middle, or lower calyceal calculi, whereas higher grades were associated with increasing stone complexity, including partial and complete staghorn calculi (Table 2). Table 2. Distribution of Patients According to Guy’s Stone Score Guy’s Stone Grade Stone Characteristics Number (n) Percentage (%) Grade I Solitary pelvic / middle / lower calyceal stone 32 64.0 Grade II Multiple stones / upper pole stone / horseshoe kidney 9 18.0 Grade III Partial staghorn calculus 6 12.0 Grade IV Complete staghorn calculus 3 6.0 Total 50 100 Operative outcomes varied significantly across Guy’s stone grades. The mean operating time increased progressively with higher grades, from 80.31 ± 12.82 minutes in Grade I to 111.67 ± 24.83 minutes in Grade III, and this difference was statistically significant (p = 0.001). Similarly, the mean hospital stay showed a significant upward trend with increasing Guy’s grade, ranging from 6.75 ± 1.24 days in Grade I to 9.00 ± 2.65 days in Grade IV (p = 0.0004). Stone-free rates declined with increasing stone complexity, being highest in Grade I (87.5%) and lowest in Grade III (16.67%) (Table 3). Table 3. Operative Outcomes According to Guy’s Stone Grade Guy’s Grade Operating Time (min), Mean ± SD Hospital Stay (days), Mean ± SD Stone-Free Rate (%) Grade I (n=32) 80.31 ± 12.82 6.75 ± 1.24 87.5 Grade II (n=9) 94.44 ± 18.11 8.67 ± 2.18 33.33 Grade III (n=6) 111.67 ± 24.83 8.67 ± 2.66 16.67 Grade IV (n=3) 110.00 ± 17.32 9.00 ± 2.65 33.33 p-value 0.001 0.0004 — Postoperative complications were observed in 16 patients (32%). Bleeding was the most common complication (50%), followed by fever (25%). Sepsis requiring intensive care was noted in 12.5% of patients, while pleural injury and transient renal function impairment each occurred in 6.25% of cases. Residual stones (>4 mm) were identified in 17 patients (34%). Among patients with residual calculi, 10 required ancillary procedures, with re-look nephroscopy performed in 80% and re-do PCNL in 20% (Table 4). Statistical analysis demonstrated a significant association between Guy’s stone grading and residual stone rate, complication profile, need for ancillary procedures, and modified Clavien grading (p < 0.05). Table 4. Post-PCNL Complications, Residual Stones, and Ancillary Procedures A.Complications (N = 16) Complication Number (n) Percentage (%) Bleeding 8 50.0 Fever 4 25.0 Sepsis (ICU care) 2 12.5 Pleural injury 1 6.25 Transient RFT increase 1 6.25 B. Residual Stones and Ancillary Procedures Parameter Number (n) Percentage (%) Residual stones (>4 mm) 17 34.0 Stone-free patients 33 66.0 Re-look nephroscopy 8 80.0 Re-do PCNL 2 20.0 Statistical significance: Guy’s stone grading showed a significant association with residual stones, complication rates, need for ancillary procedures, and modified Clavien grades (Chi-square test, p < 0.05).

Percutaneous nephrolithotomy remains the gold standard for the management of large and complex renal calculi; however, operative difficulty, complication rates, and surgical outcomes are strongly influenced by stone burden, distribution, and renal anatomy. Nephrolithometric scoring systems have therefore been developed to objectively stratify stone complexity and predict outcomes following PCNL [7]. In the present study, Guy’s stone score demonstrated a strong association with key operative and postoperative parameters, reinforcing its value as a practical preoperative assessment tool. The predominance of Guy’s stone score Grade I cases in this series mirrors routine clinical practice, where low-complexity stones are more frequently encountered. As stone complexity increased, a progressive rise in operative time and hospital stay was observed. Similar findings have been reported across multiple studies, where higher Guy’s grades were associated with prolonged procedures due to factors such as difficult access, multiple punctures, distorted calyceal anatomy, and staghorn calculi [10,12]. Systematic reviews and comparative analyses have consistently shown that nephrolithometric scores correlate well with procedural complexity and operative duration [7,13]. Stone-free rates declined significantly with increasing Guy’s grades in the present study, with optimal clearance achieved in Grade I stones and markedly lower rates in Grades III and IV. This trend is well documented in existing literature, where partial and complete staghorn calculi are associated with incomplete clearance and a higher likelihood of residual fragments [10,12]. The increased requirement for ancillary procedures in higher grades further reflects the technical challenges of achieving complete stone clearance in complex renal anatomy [7,13]. Postoperative complications were observed in nearly one-third of patients, with bleeding being the most common adverse event. Minor complications predominated in lower Guy’s grades, while major complications—including sepsis, pleural injury, and intensive care admission—were more frequent in higher grades. Previous studies evaluating PCNL complications have similarly reported an escalation in both frequency and severity of complications with increasing stone complexity [8,9]. The modified Clavien grading in this study further highlighted a shift toward higher-grade complications in advanced Guy’s grades, consistent with published validation studies [10,12]. -The significant association between Guy’s stone score and operative outcomes, complication rates, and need for ancillary procedures underscores its clinical utility. Compared with other scoring systems, Guy’s stone score offers simplicity, acceptable interobserver reliability, and ease of application using standard imaging, making it particularly suitable for routine use and resource-limited settings [11,12]. Despite these strengths, the study is limited by its single-center design and relatively small sample size, which may restrict generalizability. Additionally, variability in surgeon expertise and institutional protocols may have influenced outcomes, as noted in previous evaluations of PCNL scoring systems [7,13]. Nevertheless, the findings support the routine incorporation of Guy’s stone score into preoperative planning to facilitate risk stratification, patient counseling, and optimization of surgical outcomes.

The present study demonstrates that Guy’s stone score is a reliable and practical tool for grading procedural complexity in patients undergoing percutaneous nephrolithotomy. Increasing Guy’s grades were significantly associated with longer operative time, prolonged hospital stay, lower stone-free rates, higher complication severity, and increased need for ancillary procedures. Patients with lower-grade stones achieved better surgical outcomes with minimal morbidity, whereas higher-grade stones were linked to greater technical difficulty and postoperative complications. Owing to its simplicity, reproducibility, and dependence on routine imaging, Guy’s stone score can be effectively incorporated into preoperative evaluation. Its routine application facilitates better surgical planning, risk stratification, and informed patient counseling, ultimately improving clinical decision-making and outcome prediction in PCNL practice.

1. Adapala RKR, Prabhu GGL, 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(7-8):548-553. doi: 10.1159/000505979. Epub 2021 Mar 10. PMID: 33691327. 2. Thomas K, Smith NC, Hegarty N, Glass JM. The Guy's stone score--grading the complexity of percutaneous nephrolithotomy procedures. Urology. 2011 Aug;78(2):277-81. doi: 10.1016/j.urology.2010.12.026. Epub 2011 Feb 17. PMID: 21333334. 3. Kumar U, Tomar V, Yadav SS, Priyadarshi S, Vyas N, Agarwal N, Dayal R. STONE score versus Guy's Stone Score - prospective comparative evaluation for success rate and complications in percutaneous nephrolithotomy. Urol Ann. 2018 Jan-Mar;10(1):76-81. doi: 10.4103/UA.UA_119_17. PMID: 29416280; PMCID: PMC5791463. 4. Khan N, Nazim SM, Farhan M, Salam B, Ather MH. Validation of S.T.O.N.E nephrolithometry and Guy's stone score for predicting surgical outcome after percutaneous nephrolithotomy. Urol Ann. 2020 Oct-Dec;12(4):324-330. doi: 10.4103/UA.UA_136_19. Epub 2020 Aug 10. PMID: 33776327; PMCID: PMC7992530. 5. Farhan M, Nazim SM, Salam B, Ather MH. Prospective evaluation of outcome of percutaneous nephrolithotomy using the 'STONE' nephrolithometry score: A single-centre experience. Arab J Urol. 2015 Dec;13(4):264-9. doi: 10.1016/j.aju.2015.07.006. Epub 2015 Aug 29. PMID: 26609445; PMCID: PMC4656797. 6. Vernez SL, Okhunov Z, Motamedinia P, Bird V, Okeke Z, Smith A. Nephrolithometric Scoring Systems to Predict Outcomes of Percutaneous Nephrolithotomy. Rev Urol. 2016;18(1):15-27. PMID: 27162508; PMCID: PMC4859924. 7. Goyal NK, Goel A, Sankhwar SN, Singh V, Singh BP, Sinha RJ, Dalela D, Yadav R. A critical appraisal of complications of percutaneous nephrolithotomy in paediatric patients using adult instruments. BJU Int. 2014 May;113(5):801-10. doi: 10.1111/bju.12506. Epub 2014 Feb 14. PMID: 24127943. 8. Joshi R. Complications and Success Rate of Percutaneous Nephrolithotomy in Renal Stone: A Descriptive Cross-sectional Study. JNMA J Nepal Med Assoc. 2019 Nov-Dec;57(220):444-448. doi: 10.31729/jnma.4723. PMID: 32335659; PMCID: PMC7580408. 9. Illahi Bux K, Rizwan Ahmed R, Farooq F, Daggula NR, Mahmood J, Wasim U, Kumari S, Jan M, Khan F, Kumari U. Clinical Utility of S.T.O.N.E, Guy's Scoring System, and Renal Stone Complexity Scoring in Predicting Outcome of Single-Tract Percutaneous Nephrolithotomy. Cureus. 2023 Dec 23;15(12):e50983. doi: 10.7759/cureus.50983. PMID: 38259369; PMCID: PMC10801671. 10. Srivastava A, Yadav P, Madhavan K, Sureka SK, Singh UP, Kapoor R, Ansari MS, Lal H, Mishra P. Inter-observer variability amongst surgeons and radiologists in assessment of Guy's Stone Score and S.T.O.N.E. nephrolithometry score: A prospective evaluation. Arab J Urol. 2019 Dec 18;18(2):118-123. doi: 10.1080/2090598X.2019.1703278. PMID: 33029417; PMCID: PMC7473116. 11. Singla A, Khattar N, Nayyar R, Mehra S, Goel H, Sood R. How practical is the application of percutaneous nephrolithotomy scoring systems? Prospective study comparing Guy's Stone Score, S.T.O.N.E. score and the Clinical Research Office of the Endourological Society (CROES) nomogram. Arab J Urol. 2017 Jan 12;15(1):7-16. doi: 10.1016/j.aju.2016.11.005. PMID: 28275512; PMCID: PMC5329720. 12. 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 Jan;30(1):13-23. doi: 10.1089/end.2015.0278. Epub 2015 Dec 1. PMID: 26414226.