|Year : 2022 | Volume
| Issue : 1 | Page : 13-16
Structural and functional changes after standard percutaneous nephrolithotomy
Kalpesh Saswade, Lal Darsan, Biju S Pillai, H Krishna Moorthy
Division of Urology, Institute of Nephro-Urology, Lourdes Hospital, Kochi, Kerala, India
|Date of Submission||26-Apr-2022|
|Date of Decision||03-May-2022|
|Date of Acceptance||11-May-2022|
|Date of Web Publication||14-Jul-2022|
Dr. Biju S Pillai
Division of Urology, Institute of Nephro.Urology, Lourdes Hospital, Kochi - 682 012, Kerala
Source of Support: None, Conflict of Interest: None
Introduction: The surgical treatment of kidney stones more than 2 cm in size has been vastly simplified with the popularisation of percutaneous nephrolithotomy (PCNL) since the 1980s. However, technological revolution has witnessed miniaturisation of endoscopic instruments claiming more advantages over the usage of conventional instruments. However, the cost of smaller instruments and the higher expertise needed while using these miniature instruments have forced many surgeons to persist with the conventional procedures. Aims and Objectives: This study was intended to evaluate the structural and functional changes occurring in the kidneys after performing standard PCNL. Materials and Methods: Standard PCNL was done in 92 patients with renal stones of more than 2 cm using 25 Fr adult nephroscope. Pre-operative estimated glomerular filtration rate (eGFR) was calculated a day before the procedure and compared with post-operative eGFR estimated at 3 months. Structural changes occurring after PCNL were studied using USG renal morphometry and scarring at 3 months and compared these observations with pre-operative findings. Results: It was observed that the mean eGFR post-operative was 84.48 ± 32.18 ml/min (at 3 months) versus 77.61 ± 30.15 ml/min preoperatively (P < 0.05). The mean change of renal parenchymal thickness on post-operative USG versus pre-operative USG was insignificant (2.19 ± 0.32 cm vs. 2.22 ± 0.34 cm). There was no correlation between age and gender for change in eGFR. A mild positive correlation (correlation coefficient [r] = 0.065) was found between eGFR change and stone burden. Sixteen patients out of 92 were found to have renal scarring (>10% decrease in parenchymal thickness). Conclusions: We conclude that standard PCNL could be performed in indicated patients without apprehensions about functional loss or structural damage due to the procedure.
Keywords: Estimated glomerular filtration rate, morphometry, percutaneous nephrolithotomy
|How to cite this article:|
Saswade K, Darsan L, Pillai BS, Moorthy H K. Structural and functional changes after standard percutaneous nephrolithotomy. Kerala Surg J 2022;28:13-6
|How to cite this URL:|
Saswade K, Darsan L, Pillai BS, Moorthy H K. Structural and functional changes after standard percutaneous nephrolithotomy. Kerala Surg J [serial online] 2022 [cited 2022 Sep 24];28:13-6. Available from: http://www.keralasurgj.com/text.asp?2022/28/1/13/350884
| Introduction|| |
Urolithiasis is a disease that has long plagued human civilisation. The first report of renal stone removal through nephrostomy was in 1941 by Rupel and Brown. Renal stone surgery has evolved over the years since then to its current form of minimally invasive surgeries. The goal of stone treatments has shifted from stone-free status to achieve a stone-free state with the least renal damage., Standard percutaneous nephrolithotomy (PCNL) is the treatment of choice for renal stones larger than 2 cm in size. At a time, when standard PCNL is competing with its own miniature forms and other minimally invasive surgeries, questions regarding the damage to renal parenchyma caused by standard PCNL persists., This study was intended to evaluate the structural and functional changes occurring in the kidneys after performing standard PCNL.
Aims and objectives
This study was conducted to evaluate structural changes following standard PCNL by comparing pre-operative and post-operative ultrasonological renal morphometry. Further, it was intended to evaluate functional changes following standard PCNL by comparing pre-operative and post-operative estimated glomerular filtration rate (eGFR).
| Materials and Methods|| |
A prospective study was conducted on patients undergoing standard PCNL fulfilling inclusion criteria at a tertiary care centre for 1 year. A total of 92 patients undergoing standard PCNL for unilateral stone disease with normal contralateral kidney were included in the study. Patients with previous stone surgeries, recent pyelonephritis, chronic kidney disease and long-standing obstructive renal stones were excluded from the study.
Preoperatively, patients were evaluated with Ultrasonogram (USG) abdomen and non-contrast computerised tomogram or intravenous urogram after the routine workup which included haemogram, urine routine examination, urine culture, blood chemistry and bleeding and clotting time measured using standard laboratory methods. Standard PCNL was done in all patients under general anaesthesia in the prone position with single tract of 30 Fr into lower pole calyx by a senior surgeon with more than 10 years of experience using 25 Fr adult nephroscope and serial Alken dilators. Cases requiring multiple punctures were not included in the study. Pre-operative eGFR using Cockcroft–Gault formula (CCr = [([l40–age] × weight)/(72 × SCr)] × 0.85 [if female]) was calculated a day before the procedure and compared with post-operative eGFR estimated at 3 months. Structural changes occurring after PCNL were studied using USG renal morphometry and scarring at 3 months and comparing it with pre-operative findings. Renal morphometry included mean parenchymal thickness of three values measured at the lower pole (puncture site). Renal scarring was defined as decrease in parenchymal thickness of more than 10% as compared to pre-operative scan. The outcome variables assessed were age, sex, stone burden, stone location, stone laterality and body mass index (BMI). BMI (BMI = mass [kg]/height [m]) was calculated and all the patients were categorised as underweight (BMI <18.5), normal weight (BMI 18.5–23), overweight (23.1–27.5) and obese (BMI >27.5) according to the latest WHO guidelines for the Asian population.
Statistical analysis was done using the Student's t-test, Chi-square test and correlation and regression analysis with IBM SPSS 23 (SPSS-IBM India, 2020). The study was conducted after obtaining institutional ethical committee clearance and informed consent from the patients.
| Results|| |
A total of 92 patients were enrolled with a mean age of 48.91 years (27–71 years). The majority of patients belonged to the 41–50 years age group and males constituted 60.87%. The mean stone burden was 516.09 ± 239.66 mm2 with 25% in the 400–600 mm2 group. The demographic details of patients enrolled age given in [Table 1].
The majority of patients in the study were overweight (44/92, 47.83%), whereas normal weight patients were (24/92, 26.08%) and obese were (24/92, 26.08%). [Figure 1] gives a graphical representation of the BMI distribution of patients in the study.
The mean eGFR post-operative was 84.48 ± 32.18 ml/min (at 3 months) versus 77.61 ± 30.15 ml/min preoperatively (P < 0.05). The mean change of renal parenchymal thickness on post-operative USG versus pre-operative USG was insignificant (2.19 ± 0.32 cm vs. 2.22 ± 0.34 cm). There was no correlation between age and gender for change in eGFR. A mild positive correlation (correlation coefficient [r] = 0.065) was found between eGFR change and stone burden [Figure 2]. Sixteen patients out of 92 were found to have renal scarring (>10% decrease in parenchymal thickness). The mean stone burden was higher in the patients with scarring (P < 0.05) [Figure 3].
|Figure 2: Correlation between eGFR change and stone burden. eGFR: Estimated glomerular filtration rate|
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|Figure 3: Mean stone burden in patients with scarring versus without scarring|
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| Discussion|| |
Urolithiasis is a common disorder affecting humankind for ages. Modalities for stone removal include various minimally invasive procedures, and standard PCNL is the treatment of choice for renal stones more than 2 cm. Apprehensions have been present for the early days of PCNL regarding the damage caused to the renal parenchyma.
According to the scientific literature by Kukreja et al., patients with renal insufficiency consist of 0.78%–17.5% of the cases handled for urinary stone disease. Dilatation for PCNL is achieved mechanically, or with the help of a balloon dilatator. Renal scar development or haemorrhage in some cases due to mechanical and balloon dilatation have been matched in some animal experiments or clinical studies. Hence, morphological changes and functional changes after PCNL may be a possibility in these patients. Thus, compromised renal function may constitute a drawback to standard surgical treatment and cause bias in favour of more conservative measures. However, studies which have tried to assess the impact of PCNL on renal outcomes, both functional and morphological, are lacking, especially in Indian settings. This study tried to evaluate the impact of PCNL on renal functional and morphological outcomes and post-stone removal. In our study, a total of 92 patients with nephrolithiasis were enrolled, with a mean age of 48.91 + 10.83 years. Patients were predominantly males (56/92, 60.87%). These findings were very similar to the study by Yalcinkaya et al., where the mean age was found to be 45.2 ± 13.5 years and the proportion of males was found to be 57.81% (37/64). In the study by Tabibi et al., the mean age was found to be 45.63 years (standard deviation [SD] not mentioned) and the proportion of 49 males was very similar to that reported in our study (316/486, 65.02%). The demographic details were similar to the study by Kukreja et al.
The renal stone characteristics were analysed and found that although the majority of patients had left-sided stones (52.17%), this was not statistically significant. The most common location of the renal stone was renal pelvis (43.47%), followed by staghorn calculi (26%). The mean stone burden in the study was 516.09 ± 239.66 mm2, the most common range being 400–600 mm2 (25%), followed by 200–400 m2 range (23%). In the study by Yalcinkaya et al., the majority of stones were found on the left side (59.4%). Furthermore, the most common location of stone was pelvis (54.7%), followed by staghorn calculi type (39.1%) and the mean stone size was found to be 522 ± 171 mm2. In the study by Tabibi et al., the laterality finding was similar to that in our study (left: 51.85%). The most common subtype of stone was, however, found to be partial staghorn and the staghorn type. In the study by Kukreja et al., the laterality was slightly more common on the right side (53%), and the stone size was also higher than in most other studies (1564.28 ± 1567.85 mm2). The complex type of stone was the most common in this study, followed by the pelvic and the staghorn type.
The mean post-operative eGFR (at 3 months) showed significant improvement. This improvement in renal function may be secondary to relief of obstruction and treatment of infection. However, it can be safely inferred that the procedure does not cause any significant functional loss. Extents of the stone disease, multiple procedures as well as stone recurrence also have negative impact on renal function according to the study published by Marangella et al. In our study, the mean eGFR significantly increased postoperatively (84.48 + 32.18 versus 77.61 + 30.15 preoperatively, P < 0.05). The mean percentage change was found to be 10% (SD: 14%). In the study by Tabibi et al., the early effects of PCNL on eGFR were evaluated in various post-operative times and the authors determined the correlation of various variables with significant post-operative GFR decline after PCNL. The mean pre-operative GFR was found to be 87.85 ± 29.41 ml/min/1.73 m2. GFR significantly reduced in 1 and 2 days after PCNL (P < 0.0001 and P < 0.05) but reverted to near preoperative value in the 3rd post-PCNL month. Among various variables, only perioperative bleeding (cut-off point for serum haemoglobin drop was 2.8 mg/dL) was concomitant with significant post-operative renal function loss. In addition, comorbidities, multiple punctures, large or multiple stones and previous history of stone surgery have no significant effect on surgical outcomes. Post-operative GFR returned to near pre-operative values in a few days after PCNL. A study by Gupta et al. in 1997–1998 assessed the change in renal function before and after definitive treatment. In the 20 patients included, the stone in the affected kidney was successfully extracted using PCNL without any significant morbidity. The mean pre-operative total GFR was 65.48 ml/min (SD ± 41.02) while the mean post-operative total GFR was 62.54 (SD ± 39.07) at the 3rd month which was slightly decreased in the post-operative period unlike our study, where we found significant improvement in GFR. In a study by Pérez-Fentes et al. to assess the functional effects of PCNL and its outcomes in the operated kidney, 30 consecutive cases undergoing PCNL were selected. Kidney function was evaluated preoperatively and 3 months after surgery with serum creatinine, eGFR and 99m Tc-DMSA single-photon emission computed tomography-computed tomography scans to determine the differential renal function. The mean pre-operative eGFR (ml/min) was 74.7 ± 24.5 and mean post-operative eGFR was 77.4 ± 22.5 (P = 0.355) which showed improvement in eGFR similar to our study.
We tried to assess the association as well as the correlation of various factors which may impact the functional outcome of PCNL, which is eGFR. The age as well as gender of the patient did not have significant correlation with eGFR (P > 0.05). The stone location as well as the stone laterality did not impact the change in mean eGFR after PCNL. On assessing the correlation between stone size burden and eGFR, although mild positive correlation was noted, this was not a significant finding. This shows that improvement in eGFR may not be significantly influenced by intrinsic factors such as age, gender, stone laterality and stone location or burden. In the study by Kukreja et al., it was revealed that age <15 years, atrophic renal parenchyma, large stone burden, proteinuria >300 mg/day at follow-up and recurrent urinary infection were significant predictors of post-operative renal function deterioration.
We assessed the change in parenchymal thickness by USG, and a patient having decrease of >10% was considered to have renal scarring. Sixteen of the 92 patients were found to have renal scarring by this method. On assessing the impact of renal scarring on parameters assessed, no significant difference was witnessed in mean serum creatinine and eGFR levels between scarred and non-scarred study groups. However, one significant finding was that the scarred kidney group had a significantly higher stone burden, which explains the post-PCNL procedure scarring due to extra efforts taken during the procedure due to higher stone burden. In the study by Yalcinkaya et al., similar findings were noted as seen in our study. No significant difference between the eGFR was noted between renal cortical defect positive and negative groups. In another study by Akman et al., the renal focal cortical defect was noted in 18%.
With regards to the scarred kidney status, the mean BMI was found to be significantly higher in the group of patients who had scarred renal parenchyma (P < 0.05). Various studies have tried to extensively assess whether BMI actually influences the outcome of PCNL. In a study by Koo et al., statistically significant differences in operative duration, post-operative analgesic use and reduction in haemoglobin concentration, hospital stay and stone-free rates were not found; nor was there a greater complication rate in patients who were obese. The authors concluded that the outcome of PCNL is independent of the patients' BMI and outcomes can be favourable in most of the patients. In this study, it was thus advocated that obese patients with symptomatic stone disease should be managed based on individual status, utilising percutaneous surgery when suitable.
| Conclusions|| |
Standard PCNL could be performed in indicated patients without apprehensions about functional loss or structural damage due to the procedure.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]