The data of patients over 65 years who underwent PNL due to staghorn stones in the supine or prone position at the Urology Clinic of the Bakirkoy Dr. Sadi Konuk Training and Research Hospital between 2012-2022 was retrospectively examined. The study was approved by the local ethics committee (decision number: 2022-05-13). A staghorn stone was defined as a stone located occupying the renal pelvis and at least two renal calyces [14]. Patients with neuromuscular diseases, congenital kidney anomalies, coagulation disorders, skeletal deformities, and solitary kidneys were excluded from the study. The patients’ demographic and clinical characteristics of the cases (age, sex, body mass index [BMI], hydronephrosis grade, Charlson comorbidity index [CCI], and American Society of Anesthesiology classification [ASA]), perioperative data (surgery and fluoroscopy times, kidney access location, and number of accesses), and outcomes (SFR, hemoglobin decrease, length of hospital stay, complications, and need for retreatment) were compared. Postoperative complications were classified according to the modified Clavien-Dindo scoring system [16].
Preoperatively, all patients were evaluated using a complete blood count, serum biochemistry, urinalysis, and urine culture analysis. Operations were performed when urine cultures were sterile. Preoperative radiological assessment was undertaken in all patients using low-dose non-contrast computed tomography (NCCT). Stone dimensions, stone burden (maximum length x width), stone location, hydronephrosis grade, and stone density (Hounsfield unit) were recorded.
All operations were performed under general anesthesia. Supine PNL was performed in the Galdakao-modified Valdivia position, and a 5-French (F) ureteral catheter was retrogradely inserted in this position (17). For prone PNL, a 5-F ureteral catheter was placed retrogradely in the lithotomy position, and then the patients were placed in the prone position. In both positions, access to the pelvicalyceal system was achieved with an 18-gauge percutaneous access needle advanced into the appropriate calyx through the ureteral catheter under fluoroscopy following retrograde pyelography. After the tract was created with an Amplatz dilator set, a 22-30-F Amplatz sheath was placed, and access was achieved with a 19-F or 24-F rigid nephroscope (Karl Storz, Tuttlingen, Germany). In all operations, fragmentation was performed with a pneumatic lithotripter. Fragments were extracted using stone forceps and irrigation. An additional calyx access was created in the same manner when necessary. In cases where retrograde intrarenal surgery was required for additional intervention, a 9.5/11.5-F access sheath (Flexor® Ureteral Access Sheath, Cook Medical, IN, USA) was placed over a hydrophilic guidewire, and a Flex X-2® (Karl Storz, Tuttlingen, Germany) flexible ureterorenoscope (f-URS) was utilized. Holmium-YAG laser lithotripsy was performed with a 200-/365-μm YAG laser fiber. The laser settings were set to 0.5–2.0 J and 5–10 Hz.
Kidney, ureter, and bladder radiography was primarily used to evaluate residual stones seven to 10 days after the surgical procedure. In the first month, all patients were evaluated using NCCT to evaluate their stone-free status (SFS), which was defined as residual fragments < 4 mm. In cases where necessary, extracorporeal shock wave lithotripsy (ESWL), PNL, and f-URS lithotripsy were employed as additional interventions, and the final SFS was determined.
Statistical Analysis
Continuous data underwent evaluation using the Kolmogorov-Smirnov test to confirm the normality of variable distribution. If the data were normally distributed, the mean along with the standard deviation (SD) was used for representation; otherwise, for non-normally distributed data, median and percentile values (25-75th) were employed. Categorical data were shown by indicating the number and percentage of columns. To compare two independent, normally distributed datasets, the independent-samples t-test was utilized. In cases where the data lacked a normal distribution, the Mann-Whitney U-test was performed for comparison. For the analysis of categorical variables, the appropriate statistical test, such as Pearson's chi-square, Yate's corrected chi-square, or the Exact test, was chosen based on the circumstances. P value of <0.05 was considered statistically significant. SPSS software (version 23.0; IBM Corporation, Armonk, NY, USA) was used for statistical analyses.