Percutaneous nephrolithotomy (PCNL) is a well-established surgical technique for managing large or complex renal stones. Over the years, significant advancements have been made to optimize its safety, efficacy, and patient outcomes. One of the most debated aspects of PCNL is the optimal patient positioning, with the two primary approaches being the traditional prone position and the increasingly popular supine position. Both positions offer distinct advantages and limitations, influencing various perioperative parameters such as operative time, stone clearance rate, intraoperative complications, and postoperative pain. Understanding the impact of patient positioning on these factors is essential for surgeons to make informed decisions that optimize clinical outcomes. [1] The prone position has historically been the standard approach for PCNL since its introduction in the late 20th century. This positioning provides excellent access to the renal collecting system, facilitates stone fragmentation and retrieval, and minimizes the risk of bowel injury due to the posterior entry. Additionally, the prone position offers a well-established anatomical orientation, making it familiar to most urologists. [2] However, one of the primary limitations of the prone approach is the increased complexity of patient positioning and anesthesia management. The requirement for prone positioning can be particularly challenging in obese patients or those with cardiopulmonary comorbidities, as it can lead to respiratory compromise and hemodynamic instability. These concerns have led to the growing popularity of supine PCNL, which is considered a more physiologically favorable alternative. [3] The supine position offers several potential advantages over the prone approach, particularly in terms of anesthetic safety and ease of patient positioning. Supine PCNL allows for a more natural respiratory excursion, reducing the risk of hypoxia and hypercapnia, which are more commonly encountered in the prone position. [4] Moreover, supine positioning facilitates simultaneous retrograde access via ureteroscopy, providing a dual-modality approach that enhances stone clearance and minimizes the need for secondary procedures. The ability to perform endoscopic combined intrarenal surgery (ECIRS) more efficiently in the supine position can further improve stone-free rates while reducing operative time. Additionally, the supine position enables better venous return and reduces intra-abdominal pressure, which may contribute to lower bleeding risks and decreased postoperative morbidity. [5] Operative time is a critical factor influencing surgical efficiency and overall patient outcomes. It is influenced by multiple variables, including patient anatomy, stone burden, surgical experience, and access technique. Studies comparing supine and prone PCNL have reported mixed results regarding operative time. Some studies suggest that supine PCNL may lead to shorter operative times due to the ease of fluoroscopic guidance, less complex patient positioning, and the ability to perform simultaneous endoscopic procedures. [6] Conversely, other reports indicate that prone PCNL maintains a more favorable anatomical alignment for renal puncture and tract dilation, potentially reducing the time required for stone fragmentation and extraction. However, overall, many meta- analyses have suggested that there is no significant difference in operative time between the two positions, and the choice of approach may ultimately depend on surgeon expertise and institutional preferences. [7] The traditional prone approach has been widely regarded as offering superior access to all calyceal regions, particularly the lower pole, which is often a challenging site for complete stone clearance. [8] However, advancements in supine PCNL techniques, including modified supine positions such as the Galdakao-modified Valdivia position, have demonstrated comparable stone clearance rates to the prone approach. The ability to integrate ureteroscopy in the supine position further enhances stone retrieval by addressing residual fragments in calyceal locations that may be difficult to access through a percutaneous approach alone. While some studies suggest a marginally higher stone-free rate in prone PCNL, particularly for complex and staghorn calculi, the differences are often clinically insignificant, and both approaches remain highly effective when performed by experienced surgeons. [9] However, the overall difference in bleeding risk between the two approaches remains controversial, as several studies have reported no significant difference in transfusion rates or major hemorrhagic complications. [10] Visceral injuries, particularly to the colon and pleura, are rare but serious complications of PCNL. The risk of colonic injury is theoretically lower in the prone position because of the posterior approach avoiding the anteriorly located bowel structures. However, in well-selected patients with proper preoperative imaging, the risk of colonic perforation is minimal in both positions. Pleural injury, which can lead to pneumothorax or hydrothorax, is more common in upper pole punctures, irrespective of patient positioning. Careful preoperative imaging, optimal selection of the puncture site, and meticulous surgical technique are essential in minimizing these risks. [11] Postoperative pain is an important consideration in determining patient recovery, hospital stay, and overall satisfaction. The extent of postoperative pain in PCNL is primarily influenced by the number of access tracts, tract dilation method, and perirenal inflammation. While both prone and supine PCNL involve renal parenchymal trauma, some studies suggest that supine PCNL may be associated with lower postoperative pain scores. [9] This could be attributed to reduced surgical stress, improved drainage dynamics, and potentially less aggressive tract dilation techniques. Additionally, the supine position allows for easier postoperative mobilization and respiratory function, which may contribute to enhanced recovery and reduced opioid requirements. However, postoperative pain is highly variable among patients, and multimodal analgesia remains the cornerstone of effective pain management in both approaches. [10] The aim of this study was to evaluate the comparative study between supine vs prone percutaneous nephrolithotomy.

The study was a prospective, comparative, randomized controlled trial conducted to compare the outcomes of prone versus supine Percutaneous Nephrolithotomy (PCNL) in patients with complex kidney stones. The study adhered to ethical guidelines and was approved by the hospital's Institutional Review Board (IRB) and Ethics Committee. The study was conducted at Dr. D.Y. Patil Medical College Hospital and Research Institute, Kolhapur, which is a Tertiary care hospital with state-of-the-art surgical facilities. The ethical review and clearance were sought from the Hospital Ethics Committee before starting the study to ensure that the research adhered to the highest ethical standards. The study was carried out over a period of two years. Inclusion Criteria: Adults aged 18 years or older, patients diagnosed with complex kidney stones greater than 2 cm in size requiring PCNL, patients with renal calculi located in the renal pelvis and calyces, patients who were physically fit for general anesthesia and could tolerate the procedure, patients who provided written informed consent to participate in the study. Exclusion Criteria: Patients with ureteric calculi or bladder calculi, Patients with uncontrolled bleeding disorders or coagulopathy, Patients with severe cardiopulmonary or neurological diseases that contraindicate general anesthesia or either prone or supine positioning, Pregnant women. Patients with congenital anomalies of the kidney or those with a solitary kidney, Patients who have undergone prior renal surgeries or radiation therapy, Patients unable to comply with the follow-up requirements or who had incomplete data available. Patients who met these criteria were randomly assigned to one of the two groups: prone or supine. The study consisted of two groups based on the patient‘s surgical position during Percutaneous Nephrolithotomy (PCNL): Group A (supine position) and Group B (prone position). Group A included patients who underwent the procedure while in the supine position, while Group B included patients who were positioned prone during the procedure.

The study population was equally distributed between the two intervention arms. Group A (Supine PCNL) and Group B (Prone PCNL) each comprised 33 patients, representing 50% of the total sample size of 66. Demographic Profile of the Study Population by Sex The study population consisted of 66 patients, with a nearly equal distribution of sexes. There were 34 male participants (51.50%) and 32 female participants (48.50%). This slight male predominance reflects the general epidemiological trend seen in renal stone disease, where males tend to be affected marginally more often. Anatomical Distribution of Renal Calculi in Study Participants The distribution of renal calculi by anatomical location highlights that the majority of stones were located in the lower pole of the kidney, accounting for 59.10% of cases. Stones in the upper pole were found in 16.70% of patients, while 15.20% had stones located in the renal pelvis. Only 9.10% of stones were identified in the middle pole. This pattern is consistent with clinical observations that the lower pole is a common site for stone lodgment due to gravity-dependent drainage and anatomical angulation. Understanding stone location is critical as it influences the choice of access tract, procedural complexity, and success of stone clearance. Table 1: Anatomical Location of Renal Calculi Among Study Participants Location Number of Patients Percentage Lower Pole 39 59.10% Middle Pole 6 9.10% Pelvis 10 15.20% Upper Pole 11 16.70% Total 66 100.00% Frequency Distribution of Number of Percutaneous Access Punctures Among the 66 patients who underwent PCNL, a single percutaneous puncture was performed in the majority (74.20%) of cases, indicating effective stone access through a single tract in most procedures. Two punctures were required in 21.20% of cases, and only 4.50% of patients required three punctures. The limited need for multiple tracts suggests effective preoperative planning and favorable anatomical orientation in most patients. However, the necessity for more than one puncture typically reflects complex stone burden or difficult calyceal anatomy, which may also influence operative time and postoperative morbidity. Table 2: Distribution of Study Participants According to Number of Punctures Required Number of Punctures Number of Patients Supine Prone Percentage 1 49 21 28 74.20% 2 14 9 5 21.20% 3 3 3 0 4.50% Total 66 33 33 100.00% Distribution of Residual Stone Fragments Post-PCNL Among the 66 patients, 80.30% achieved complete stone clearance, while 19.70% had residual stone fragments post-procedure. This indicates a high overall stone-free rate, consistent with the effectiveness of PCNL as a treatment modality for large renal calculi. The presence of residual fragments in nearly one-fifth of the patients may be attributed to factors such as complex stone morphology, calyceal location, or suboptimal tract access. Identifying such trends helps assess the efficacy of procedural techniques and guides the need for secondary interventions. Table 3: Presence of Residual Stones after PCNL Residual Stones Number of Patients Percentag e Supine Prone No 53 80.30% 20 33 Yes 13 19.70% 13 0 Total 66 100.00% 39% 0% Need for Additional Procedures Following Initial PCNL The majority of patients (84.80%) did not require any additional procedure after the primary PCNL. However, 15.20% required further interventions such as ESWL or repeat PCNL to achieve complete stone clearance. These additional procedures were more common in patients with residual fragments or challenging anatomical access. This finding underscores the importance of intraoperative clearance assessment and reinforces the value of follow-up imaging to guide further management. Table 4: Requirement of Additional Procedure Following PCNL Additional Procedure Number of Patients Supine Prone Percentage No 56 23 33 84.80% Yes 10 10 0 15.20% Total 66 33 33 100.00% Laterality of Surgical Intervention In the present study, PCNL was performed on the left side in 53% of cases and on the right side in 47%. The near-equal distribution suggests no significant laterality bias in stone presentation. Understanding laterality helps in assessing surgical access trends and may also influence the choice of positioning and tract creation, especially in cases involving anatomical variations or previous interventions. Distribution of Postoperative Pain Scores Among Study Participants Postoperative pain was assessed using the Visual Analog Scale (VAS), with scores ranging from less than 5 to 9. The most frequently reported scores were 6 (22.9%) and 5 (18.6%), indicating moderate levels of discomfort in the majority of patients. Only 14.3% of patients reported minimal pain with VAS <5, while 8.6% experienced severe pain with scores of 9. The broad range of scores suggests varying responses to surgical trauma and analgesia, potentially influenced by factors such as access tract number, stone burden, and patient sensitivity. This distribution supports the importance of multimodal analgesia and individualized pain control strategies following PCNL. Incidence of Postoperative Complications Postoperative complications were reported in 56.5% of the study population, while 44.5% had no complications. This relatively high rate of complications may reflect minor adverse events such as fever, hematuria, or mild infection, which are commonly associated with PCNL. While the exact nature and severity of complications were not specified here, these findings highlight the importance of close postoperative monitoring and prompt intervention to reduce morbidity. It also underlines the need for continued evaluation of surgical technique and perioperative care protocols to minimize risk. Comparison of Gender Distribution between Study Groups The gender distribution between Group A (Supine PCNL) and Group B (Prone PCNL) was statistically comparable. Group A consisted of 17 females and 16 males, while Group B had 15 females and 18 males. The p-value of 0.622 indicates no significant difference in sex distribution between the two groups. This balanced representation ensures that gender-related anatomical or physiological differences are unlikely to have influenced the comparative outcomes of the study and supports the internal validity of the randomization process. Intergroup Comparison of Stone Location between Supine and Prone PCNL This study demonstrated a statistically significant difference in the anatomical distribution of renal stones between the supine (Group A) and prone (Group B) PCNL groups (p = 0.005). In Group B, a higher proportion of stones were located in the lower pole (22 cases) and middle pole (6 cases), while Group A had more stones in the upper pole and pelvis. Notably, no middle pole stones were treated in the supine group. The predominance of lower pole stones in the prone group may have influenced the surgical access and outcomes, as prone positioning is often preferred for lower calyceal access. These findings suggest that stone location may have influenced positioning decisions or affected procedural outcomes, highlighting the need for individualized access planning based on anatomical complexity. Comparison of Number of Punctures between Supine and Prone PCNL Groups The number of access punctures required during PCNL varied between the two groups. In Group A (Supine), 63.6% of patients required only a single puncture, while in Group B (Prone), this was higher at 84.8%. Two punctures were performed in 27.3% of supine cases compared to 15.2% in the prone group. Three punctures were necessary in 9.1% of supine cases, whereas none in the prone group required three. Although more multiple punctures were observed in the supine group, the difference was not statistically significant (p = 0.076). This suggests a trend but not a definitive association between positioning and number of punctures. Comparison of Residual Stone Fragments between Supine and Prone PCNL A significant difference was observed in residual stone rates between the two groups. While all patients in the prone group (100%) had no residual fragments postoperatively, 39.4% of patients in the supine group had residual stones. The p-value was <0.001, indicating a statistically significant difference favoring the prone position for achieving complete stone clearance. This result may reflect the advantages of prone access in targeting certain anatomical locations or accommodating more favorable instrument angulation. Comparison of Need for Additional Procedures Between Groups The need for additional procedures was significantly higher in the supine group. While none of the patients in the prone group required a secondary intervention, 30.3% (10 patients) in the supine group needed further treatment such as ESWL or repeat PCNL. The difference was statistically significant (p = 0.001), highlighting a potential clinical disadvantage of the supine position in achieving optimal stone clearance in a single session. Comparison of Laterality between Supine and Prone PCNL Groups There was no significant difference in the laterality of surgical intervention between the two groups. In Group A (Supine), 54.5% of cases were left-sided and 45.5% were right-sided. In Group B (Prone), left and right-sided interventions were nearly evenly distributed at 51.5% and 48.5%, respectively. The p-value of 0.805 confirms that laterality was evenly matched between the groups and unlikely to have influenced outcome variations. Comparison of Postoperative Pain Scores between Groups Postoperative pain assessment using VAS showed comparable pain distribution in both groups. In the supine group, 24.2% of patients reported minimal pain (VAS <5) compared to only 6.1% in the prone group. Moderate pain scores (VAS 5–7) were observed in most patients of both groups, while higher scores (VAS 8–9) were slightly more frequent in the prone group. Although the supine group trended toward lower pain levels, the difference did not reach statistical significance (p = 0.316). This suggests that both positions yield similar pain profiles, with potential subjective variation. Comparison of Postoperative Complications between Groups Postoperative complications occurred in 54.5% of patients in the supine group and 51.5% in the prone group. The difference was not statistically significant (p = 0.505). The comparable rates suggest that both surgical positions have similar safety profiles in terms of complication frequency. Further analysis of complication types (e.g., fever, bleeding) would provide deeper insights, but the current data imply no procedural advantage in terms of complication prevention. Intergroup Comparison of Baseline and Operative Parameters The median values (with interquartile ranges) for age, BMI, stone size, hospital stay, and operative time were compared between the two groups. Age, BMI, and stone size were statistically comparable between Group A (Supine) and Group B (Prone), with p-values of 0.928, 0.878, and 0.72 respectively, confirming successful randomization and demographic balance. However, a significant difference was observed in hospital stay duration, with the supine group having a longer median stay (6.51 vs 6 days; p = 0.01), suggesting slightly slower postoperative recovery. Operative time was marginally lower in the supine group, but the difference did not reach statistical significance (p = 0.058). These findings support overall group comparability with a potential advantage for the prone position in reducing hospital stay. Table 5: Intergroup Comparison of Age, BMI, Stone Size, Hospital Stay, and Operative Time Parameter Group A – Median (Q1, Q3) Group B – Median (Q1, Q3) p- value Age (years) 35 (27.5, 50) 36 (28.5, 47) 0.928 BMI (kg/m²) 26.4 (24.2, 28.5) 26.8 (24.8, 28.6) 0.878 Stone Size (cm) 2.5 (2.4, 2.7) 2.6 (2.45, 2.65) 0.720 Hospital Stay (days) 6.51 (6, 7.51) 6 (5.14, 7.11) 0.010 Operative Time 106.34 (92.62, 120.25) 132.65 (130.60, 140.0) 0.058

One of the primary findings was that hospital stay was significantly shorter in the prone group compared to the supine group (p = 0.01), while operative time was marginally longer in the prone group, though not statistically significant (p = 0.058). This partially aligns with Mazzucchi et al. [12], who observed that supine PCNL resulted in a shorter hospital stay and reduced operative time. However, in contrast, our study found a longer hospital stay in the supine group, which may be attributed to institutional discharge protocols, postoperative observation preferences, or variations in patient recovery patterns. Regarding stone clearance, our results showed a significantly higher rate of stone-free status in the prone group, with no residual stones observed, compared to 39.4% of patients with residual stones in the supine group (p < 0.001). This finding differs from several studies including those by Sohail et al. [13] and Perrella et al. [14], where supine PCNL showed similar or even superior stone-free rates compared to prone PCNL. A possible explanation for our divergent result could be the surgical learning curve associated with the supine technique or anatomical access limitations that reduced visibility or reach during the procedure. In terms of complications, the current study reported no significant difference between the two groups (p = 0.505), which mirrors the findings of Yuan et al. [15], Adl [16], and McCahy et al. [17], all of whom concluded that complication rates were statistically similar between both positions. Nonetheless, our study observed a slightly higher frequency of complications in the supine group, though not statistically significant, which is consistent with findings by Sohail et al. [13], who reported significantly fewer complications in supine PCNL. Pain scores assessed using the Visual Analog Scale (VAS) were not significantly different between the two groups in our study (p = 0.316). This contrasts with the results from Ratkal et al. [18], who found significantly lower VAS scores in supine patients, attributing this to the ergonomic advantages and potentially less muscular disruption in the supine position. Our findings may be influenced by uniform postoperative analgesic administration across both groups or varying individual pain thresholds. Furthermore, the number of punctures required was lower in the prone group, although the difference did not reach statistical significance (p = 0.076). This result contrasts with studies such as that by Keshavamurthy et al. [19], where fewer punctures were noted in supine procedures. Our observed trend might reflect anatomical access challenges or surgeon preference influencing the choice of calyceal puncture site. Lastly, the requirement for additional procedures was significantly higher in the supine group (p = 0.001), indicating more frequent incomplete stone clearance or intraoperative challenges necessitating secondary interventions. This diverges from findings by Ratkal et al. [18] and Choudhury et al. [20], where fewer auxiliary procedures were needed in supine PCNL, likely due to the ability to perform combined procedures such as simultaneous ureteroscopy.

A significantly shorter hospital stay was observed in the supine group, along with reduced requirement for additional procedures and a lower incidence of residual calculi, underscoring the procedural completeness and technical ease associated with the supine approach. Although differences in postoperative complications and pain scores were not statistically significant, trends favored the supine position, indicating a potential for reduced morbidity. Furthermore, the supine group required fewer punctures, suggesting easier anatomical access and potentially less parenchymal damage. These findings align with several contemporary studies advocating for the supine position as a viable and increasingly preferred alternative to the prone approach. While both techniques remain effective and safe, supine PCNL appears to offer added benefits in terms of patient comfort, anesthesia management, and surgical workflow, without compromising outcomes. Given the simplicity, shorter operative and hospitalization times, and comparable safety profile, supine PCNL should be considered a standard option in the surgical management of renal calculi, particularly in settings requiring procedural efficiency and patient-centered care. Future studies with larger sample sizes, longer follow-up periods, and inclusion of functional renal outcomes will further validate and refine the role of supine PCNL in clinical practice.

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