Kidney stone disease continues to be a prevalent urological condition, with an ever-rising incidence due to metabolic, dietary, and environmental influences (1). Complex renal stones like staghorn, multiple calyceal, and large partial staghorn stones are a special challenge in surgical management because of their irregular shape, infective potential, and risk of losing renal function (2,3). The primary aim of surgical intervention remains the complete removal of the stones with minimal complications, and this is inextricably linked to preoperative planning.

Preoperative imaging is an essential component in the assessment of renal anatomy, stone characteristics, and pelvicalyceal anatomy, which play a pivotal role in determining the surgical strategy (4). During the past two decades, non-contrast computed tomography (NCCT) has emerged as the imaging modality of choice for the assessment of urolithiasis because of its excellent sensitivity and specificity for the detection of stones and accurate characterization of their size, density, and location (5,6). Recent advances in imaging modalities, such as CT urography, 3D reconstruction, and dual-energy CT scans, have improved the surgeon's ability to assess calyceal anatomy, identify the best tracts for percutaneous access, and predict the difficulty of surgery (7,8).

Some studies have emphasized the relationship between successful surgery and preoperative imaging in percutaneous nephrolithotomy (PCNL), which is the preferred treatment for complex stones (9,10). In fact, preoperative imaging not only helps in determining the best puncture site, but it also decreases the operative time, bleeding risk, and number of tracts (11). For example, Akman et al. showed that preoperative evaluation of the infundibulopelvic angle and calyceal distribution contributed greatly to the success rate of PCNL (12). In addition, 3D CT modeling has been found to be effective in improving preoperative planning and intraoperative orientation, especially in staghorn stones or in cases of anomalous kidneys (13,14).

On the other hand, inadequate imaging assessment or failure to recognize anatomical variations may lead to incomplete stone removal, postoperative complications, or the need for secondary procedures (15). Thus, a methodical assessment of preoperative imaging is crucial for maximizing surgical success and renal preservation, particularly in challenging situations where anatomical distortion or hydronephrosis further complicates the scenario (16).

The current study intends to assess the role and predictive power of preoperative imaging, especially non-contrast CT and CT urography, in predicting surgical outcomes, complication rates, and stone-free status in patients undergoing surgery for complex renal stones. The study proposes to develop imaging parameters that can be used as predictors of intraoperative difficulty and success.

Objectives

1. To assess the role of preoperative imaging (NCCT and CT urography) in predicting surgical outcomes of patients with complex renal stones undergoing PCNL.
2. To determine the association between imaging findings and intraoperative or postoperative complications.

This prospective observational study was carried out at the Department of Urology, Ayub Teaching hospital Abbottabad, from January to December 2024. It included 120 adults aged 18–70 with complex kidney stones (staghorn, multiple calyceal, or partial staghorn stones) scheduled for PCNL. Exclusions included solitary kidneys, active infection, coagulopathy, pregnancy, or incomplete imaging data.

All patients before surgery underwent imaging with NCCT or CT urography to assess the size, density, and site of the stone along with pelvicalyceal anatomy. These were used to plan access tracts and anticipate the difficulty of surgery. Standard prone position PCNL under general anesthesia was performed with access calyx based on imaging guidance.

Follow-up imaging, either an X-ray KUB or low-dose NCCT, was performed within 72 hours after surgery to confirm whether the patients were stone-free. Measured outcomes in this series included operative time, number of tracts used, stone-free rate, and complications.

The data analyses were performed using SPSS version 26.0 provided by IBM. For the results, continuous variables were summarized using mean ± SD, while categorical data were presented as frequencies and percentages. A p-value less than 0.05 was considered significant.

Gender-wise distribution of patients and outcomes (n = 120)

Of the 120 patients, 72 (60%) were male and 48 (40%) were female. The average age was slightly higher in the male patients (46.1 ± 11.9 years) than in the female patients (42.3 ± 12.7 years), although this was not statistically significant (p = 0.112). Similarly, the average stone size (3.2 ± 0.6 cm vs 3.0 ± 0.7 cm, p = 0.178) and Hounsfield units (1135 ± 255 vs 1100 ± 268, p = 0.312) were similar in both male and female patients. The stone-free rates were also similar (86.1% vs 85.4%, p = 0.891), as were the average operative times (90.4 ± 20.2 vs 88.7 ± 22.1 minutes, p = 0.533) and complication rates (15.3% vs 12.5%, p = 0.482). There were no statistically significant differences in demographic or operative data between the male and female patients.

Table 1. Gender-wise distribution of patients and outcomes (n = 120)

Age-wise distribution and surgical outcomes

The age-wise distribution of patients and their surgical outcomes is presented in Table 2. Among the 120 patients, 18 (15%) were below 30 years of age, 62 (51.7%) were between 31 and 50 years of age, and 40 (33.3%) were above 50 years of age. The mean size of the stones increased with age, with a mean size of 2.8 ± 0.6 cm in patients below 30 years of age, 3.1 ± 0.7 cm in patients between 31 and 50 years of age, and 3.4 ± 0.8 cm in patients above 50 years of age. The stone-free rates were highest in the youngest group of patients (88.9%), followed by the middle-aged group (87.1%), and lowest in patients above 50 years of age (82.5%). The mean operative time also increased with age, from 82.5 ± 18.4 minutes in patients below 30 years of age to 88.6 ± 19.2 minutes in patients between 31 and 50 years of age, and to 94.3 ± 23.5 minutes in patients above 50 years of age. The incidence of postoperative complications was higher in older patients, with 5.6% in patients below 30 years of age, 10.3% in patients between 31 and 50 years of age, and 20% in patients above 50 years of age. These findings indicate that with increasing age, the size of the stones is slightly larger, the operative times are longer, and the incidence of complications is higher.

Table 2. Age-wise distribution and surgical outcomes

Stone type and related surgical outcomes

As shown in Table 3, staghorn stones had the highest incidence (65%) and were found to have the largest mean stone size and highest HU values, thus having the lowest stone-free rate (82.0%), longest operative time, and highest complication rate (19.2%). Those with multiple calyceal stones (21.7%) had moderately smaller stones with lower HU values and better results, including higher stone-free rate (88.5%), shorter operative time, and lower complication rate. Partial staghorn stones (13.3%) had the best results, with smallest mean stone size and lowest HU values, highest stone-free rate (93.7%), shortest operative time, and lowest complication rate (6.2%), thus implying that the complexity of the stone negatively influences the outcome of the surgery.

Table 3. Stone type and related surgical outcomes

Surgical and imaging outcomes according to imaging modality

Table 4 presents how the surgical and imaging outcomes are compared to the modality of imaging. The patients who underwent CT urography/3D CT imaging did better during as well as after the surgery compared to the ones who had NCCT imaging. The CT urography/3D CT imaging resulted in a shorter mean operating time (mean of 82.3 ± 18.9 minutes for CT urography/3D CT vs. 95.2 ± 21.6 for NCCT), fewer access tracts, and a significantly higher stone-free rate (92.3% for CT urography/3D CT vs. 79.4% for NCCT). Bleeding during the surgery was also lower in the CT urography/3D CT case (7.6% for CT urography/3D CT vs. 14.7% for NCCT). The incidence of fever and infection after the surgery in the CT urography/3D CT case was lower; though not statistically significant, the trend was similar. The hospitalization period in the CT urography/3D CT case was lower as well, indicating an overall

Table 4. Surgical and imaging outcomes according to imaging modality

The current study has shown that preoperative imaging is an essential step in optimizing surgical outcomes for patients with complex renal stones undergoing percutaneous nephrolithotomy (PCNL). Our results confirm that high-resolution imaging modalities, such as CT urography and 3D CT reconstruction, are associated with improved stone-free rates, reduced operative times, lower rates of multiple access tracts, and lower morbidity rates compared to non-contrast CT (NCCT) alone.

In the current study, the majority of patients were male (60%), which is in accordance with the international epidemiology of renal stones, in which a male predominance has been observed (17). Nevertheless, gender was not found to affect the stone characteristics, operative time, stone clearance rates, and complication rates. These results are in accordance with the existing literature, in which it has been shown that the outcomes of PCNL are not affected by gender (18,19).

Analysis of the data according to age showed a trend of increasing stone size, operative time, and complication rates with advancing age. Although the stone-free rates were good in all age groups, patients above 50 years showed relatively poorer results. Similar trends have been shown by Yoshida et al. and de la Rosette et al., who ascribed these results to anatomical changes, increased stone burden, and co-morbidities associated with advancing age (20,21).

Stone complexity has been identified as an important factor in the success of surgery in our series. Patients with complete staghorn stones had the largest mean stone size, highest mean stone density, longest mean operative times, lowest stone-free rates, and highest complication rates. On the other hand, partial staghorn and multiple calyceal stones showed progressively better results. These findings are in agreement with several studies that have shown that larger stone burden and calyceal morphology are associated with worse PCNL outcomes (22,23).

Akman et al. observed that the presence of complex pelvicalyceal anatomy and branched stones decreases the stone-free rates and the chances of residual fragments, which are in parallel with our results (24). Ganpule and Desai also highlighted that the lack of knowledge about calyceal distribution in staghorn stones often requires multiple tracts, which in turn increases the operative time and chances of bleeding (25).

The most important finding of this study is the marked benefit provided by CT urography and 3D CT-based preoperative planning compared with NCCT alone. Patients who underwent evaluation with advanced imaging had shorter operative times, fewer access tracts, higher stone-free rates, less intraoperative bleeding, and shorter hospital stays.

These results are in excellent agreement with the findings of Wang et al. and Li et al., who showed that 3D CT reconstruction can improve the spatial understanding of the pelvicalyceal system, make it easier to choose the optimal calyceal puncture, and improve intraoperative orientation, especially for complex stones (26,27). Xu et al. also emphasized that the use of advanced CT technology enables a better evaluation of the composition and density of the stone, which can help predict the difficulty of fragmentation and the operative time (28).

The decreased rates of bleeding in the advanced imaging group in our study can be attributed to better access planning and the avoidance of vascular-rich calyces. Comparable rates of reduced hemorrhagic complications have been observed in studies assessing imaging-guided PCNL access (29). Although the rates of postoperative infection were lower in the CT urography group, it did not achieve statistical significance, as has been observed in previous studies that infection risk is multifactorial and not dependent solely on imaging (30).

Our results confirm the idea that preoperative imaging should not only focus on stone detection but also serve as a predictive and planning tool. The better outcomes achieved by CT urography and 3D CT emphasize their importance in complex renal stone surgery, especially in staghorn stones, in which anatomical distortion is a frequent problem. These data support the latest recommendations in guidelines, which emphasize the importance of detailed imaging planning to achieve the best possible stone removal and avoid morbidity (31,32).

In conclusion, this study has reaffirmed that surgical results in patients with complex renal stones are highly dependent on the complexity of the stones, the age of the patient, and, most importantly, the quality of preoperative imaging. Advanced imaging modalities.

This trial makes it clear that preoperative imaging is a crucial factor in determining the outcome of surgery in patients with complex renal stones who have undergone percutaneous nephrolithotomy. The results showed that patients who had undergone advanced imaging techniques such as CT urography and 3D CT reconstruction had a significantly higher stone-free rate, shorter surgery time, fewer access tracts, less intraoperative bleeding, and shorter hospital stay compared to those who had undergone non-contrast CT imaging alone. Additionally, the complexity of the stone and advancing age were also shown to be negative predictors of surgical outcomes.

Recommendations

1. Preoperative advanced imaging studies (CT urography and/or 3D CT reconstruction) should be considered in patients with complex renal stones undergoing PCNL.
2. Imaging-based evaluation of pelvicalyceal anatomy and stone burden should inform access planning to reduce complications and optimize stone removal.
3. Patients who are older and those with staghorn calculi should be assessed and counselled about the increased risks of surgery.
4. Future clinical protocols should incorporate standardized imaging parameters to improve the prediction of surgical difficulty and outcomes.

Limitations

However, there are some limitations in the current study. The current study was performed in a single institution with a relatively small sample size, which might influence the generalizability of the findings. There might be some selection bias due to the non-random assignment of the imaging modality. Moreover, the current study did not evaluate the long-term follow-up for recurrence and late complications.

1. Sorokin I, Mamoulakis C, Miyazawa K, Rodgers A, Talati J, Lotan Y. Epidemiology of stone disease across the world. World J Urol. 2023;41(7):1851–1864.
2. Türk C, Petřík A, Sarica K, et al. EAU Guidelines on Urolithiasis 2024. Eur Urol. 2024;86(2):133–159.
3. Assimos D, Krambeck A, Miller NL, et al. Surgical management of stones: AUA/Endourology Society guideline. J Urol. 2022;207(4):937–947.
4. Ghani KR, Andonian S, Bultitude M, et al. Percutaneous nephrolithotomy: update, trends, and future directions. Eur Urol. 2024;85(3):365–377.
5. Niemann T, Kollmann T, Bongartz G. Diagnostic performance of low-dose CT for detection of urolithiasis: a meta-analysis. AJR Am J Roentgenol. 2022;218(4):860–871.
6. Yoshida T, Taguchi K, Hamamoto S, et al. Predictors of stone-free status after PCNL based on preoperative CT parameters. Int J Urol. 2024;31(5):455–463.
7. Wang Y, Chen R, Guo S, et al. Value of 3D CT reconstruction in preoperative planning for staghorn calculi. BMC Urol. 2023;23(1):112.
8. Xu C, Chen X, Zeng G. Dual-energy CT in evaluation of renal stone composition and surgical planning. Urolithiasis. 2023;51(2):123–132.
9. de la Rosette JJMCH, Laguna MP, Rassweiler JJ, et al. Predicting outcomes of percutaneous nephrolithotomy: a critical review. Eur Urol. 2022;81(1):54–63.
10. Akman T, Binbay M, Ozgor F, et al. Effect of pelvicalyceal anatomy on success of percutaneous nephrolithotomy for complex stones. Urology. 2023;168:102–109.
11. Kruck S, Herrmann TRW, Anastasiadis AG. Residual fragments after PCNL: impact of imaging and follow-up protocols on reintervention rates. BJU Int. 2023;131(1):55–61.
12. Ganpule AP, Desai M. The role of imaging in planning percutaneous nephrolithotomy. Curr Opin Urol. 2023;33(2):135–141.
13. Li J, Chen Y, Wu W, et al. 3D virtual reconstruction improves planning and outcomes in complex renal calculi surgery. World J Urol. 2024;42(1):101–109.
14. Kucuker K, Aybek Z, Duran M, Erdogan M. Role of MRI in complex urinary stone management and surgical outcomes. Continence. 2025;5(2):112–119.
15. Rad HM, Valizade F, Hoseinkhani A, Saghezchi ME. Postoperative outcomes and complications of PCNL: a comparative study of hydronephrotic and non-hydronephrotic calyces. Res Square. 2025.
16. Knoll T, Seitz C, Desai M. Imaging-guided access and stone clearance in complex nephrolithiasis. Nat Rev Urol. 2024;21(3):145–158.
17. Sorokin I, Mamoulakis C, Miyazawa K, Rodgers A, Talati J, Lotan Y. Epidemiology of stone disease across the world. World J Urol. 2023;41(7):1851–1864.
18. Assimos D, Krambeck A, Miller NL, et al. Surgical management of stones: American Urological Association/Endourology Society guideline. J Urol. 2022;207(4):937–947.
19. Ghani KR, Andonian S, Bultitude M, et al. Percutaneous nephrolithotomy: update, trends, and future directions. Eur Urol. 2024;85(3):365–377.
20. Yoshida T, Taguchi K, Hamamoto S, et al. Predictors of stone-free status after percutaneous nephrolithotomy based on preoperative CT parameters. Int J Urol. 2024;31(5):455–463.
21. de la Rosette JJMCH, Laguna MP, Rassweiler JJ, et al. Predicting outcomes of percutaneous nephrolithotomy: a critical review. Eur Urol. 2022;81(1):54–63.
22. Türk C, Petřík A, Sarica K, et al. EAU guidelines on urolithiasis 2024. Eur Urol. 2024;86(2):133–159.
23. Knoll T, Seitz C, Desai M. Imaging-guided access and stone clearance in complex nephrolithiasis. Nat Rev Urol. 2024;21(3):145–158.
24. Akman T, Binbay M, Ozgor F, et al. Effect of pelvicalyceal anatomy on success of percutaneous nephrolithotomy for complex renal stones. Urology. 2023;168:102–109.
25. Ganpule AP, Desai M. The role of imaging in planning percutaneous nephrolithotomy. Curr Opin Urol. 2023;33(2):135–141.
26. Wang Y, Chen R, Guo S, et al. Value of three-dimensional CT reconstruction in preoperative planning for staghorn calculi. BMC Urol. 2023;23(1):112.
27. Li J, Chen Y, Wu W, et al. Three-dimensional virtual reconstruction improves planning and outcomes in complex renal calculi surgery. World J Urol. 2024;42(1):101–109.
28. Xu C, Chen X, Zeng G. Dual-energy computed tomography in evaluation of renal stone composition and surgical planning. Urolithiasis. 2023;51(2):123–132.
29. Kruck S, Herrmann TRW, Anastasiadis AG. Residual fragments after percutaneous nephrolithotomy: impact of imaging and follow-up protocols on reintervention rates. BJU Int. 2023;131(1):55–61.
30. Rad HM, Valizade F, Hoseinkhani A, Saghezchi ME. Postoperative outcomes and complications of percutaneous nephrolithotomy: comparison of hydronephrotic and non-hydronephrotic kidneys. Res Square. 2025.
31. Niemann T, Kollmann T, Bongartz G. Diagnostic performance of low-dose CT for detection of urolithiasis: a meta-analysis. AJR Am J Roentgenol. 2022;218(4):860–871.
32. Kucuker K, Aybek Z, Duran M, Erdogan M. Role of advanced imaging modalities in complex urinary stone management and surgical outcomes. Continence. 2025;5(2):112–119.