https://orcid.org/0000-0001-6859-8406
ABSTRACT
Purpose
The prevalence of urinary stone disease in ESRD is 3.2%, leading to renal damage due to obstructive uropathy, infection, and frequent surgical intervention. PCNL, the gold standard for complex renal stone disease, has evolved with smaller access sheaths (14–20 F), improved optics, and fluoroscopic equipments. This study aims to assess the safety and feasibility of mini- PCNL in CKD patients with respect to postoperative outcome and its effect on stage of CKD.
Patients and methods
This prospective study was conducted in the Department of Urology, Sher-I-Kashmir Institute of Medical Sciences, from January 2022 to October 2022. This study included adult patients with nephrolithiasis at CKD stage 3 or higher. The primary objective of this research was to assess the impact of mini-PCNL on renal function, specifically measuring changes in estimated glomerular filtration rate (eGFR) from baseline to a 6-month follow-up. The secondary objective was to evaluate the feasibility of mini-PCNL in CKD patients in terms of complications, stone clearance rate, and duration of hospital stay. Four variable Modification of Diet in Renal Diseases(MDRD) equation was used to calculate the estimated GFR(eGFR) of each patient and NKF/KDOQI classification system to classify the stage of CKD.
Results
A total of 46 patients were included in the study. We found that for management of nephrolithiasis in CKD patients, mini-PCNL leads to significant improvement in eGFR at 6 months follow-up (mean difference = 14.25 ml/min/1.73 m2; p-value <0.01) with high stone-free rates (89.5%). The complication rates were comparable to standard PCNL.
Conclusions
mini-PCNL is a bonanza for management of CKD patients with nephrolithiasis.
KEYWORDS:
Introduction
Chronic kidney disease (CKD) is defined as sustained kidney injury for more than 3 months, resulting in a glomerular filtration rate(GFR) of less than 60 ml/min/1.73 m2 by National Kidney Foundation’s Kidney Disease Outcomes Quality Initiative(NFK/KDOQI) advisory board [Citation1]. Results from SEEK (Screening and Early Evaluation of Kidney diseases) study suggests that the overall prevalence of CKD was 17.2% with prevalence of CKD stage 1, 2, 3, 4, and 5 was 7%, 4.3%, 4.3%, 0.8%, and 0.8%, respectively [Citation2].
Urolithiasis is a recognized risk factor for CKD. The prevalence of urinary stone disease in ESRD (end-stage renal disease) is reported to be 3.2% [Citation3]. There are a multitude of options for management of nephrolithiasis in CKD patients including Extracorporeal shock wave lithotripsy (ESWL), Retrograde intrarenal surgery (RIRS), laparoscopy or Percutaneous nephrolithotomy (PCNL). PCNL has emerged as the gold standard treatment for large burden and complex renal stone disease with maximum stone free rates in a single setting. The procedure of PCNL has evolved with miniaturization of access sheath, better optics and better fluoroscopic equipments. Standard PCNL is done with sheath size of 24 to 30 F, whereas the mini-PCNL/Miniperc is done with sheath size 14 to 20 F [Citation4]. Mini-PCNL had a shorter hospital stay, less haemoglobin drop, less need of blood transfusion, greater postoperative tubeless and fewer complications, when compared to Standard-PCNL. Studies have shown that stone-free rate (SFR), fever, and postoperative pain were similar in both of them [Citation5].
There is paucity of data in existing literature regarding the status of mini-PCNL in nephrolithiasis with CKD patients. This study aims to assess the safety and feasibility of Mini-PCNL in CKD patients with respect to postoperative outcome and its effect on stage of CKD.
Material and methods
Study design
This prospective study was undertaken in the Department of Urology at the Sher-I-Kashmir Institute of Medical Sciences between January 2022 and October 2022, with prior approval from the institutional ethics committee. All patients participating in the study provided informed consent. Inclusion criteria consisted of adult patients with nephrolithiasis at CKD stage 3 or higher, while exclusion criteria included patients who declined consent for PCNL, those with unmanaged bleeding diathesis, pregnant individuals, and pediatric patients under 18 years of age.
Objectives
The primary outcome of the study was to assess the effect of mini-PCNL on renal function in terms of improvement/deterioration in eGFR from baseline to follow up at 6 months. Secondary outcome of the study was to assess the feasibility of mini-PCNL in CKD patients in terms of complications, SFRs, hospital stay.
Methods
We used four variable Modification of Diet in Renal Diseases (MDRD) equation to calculate the estimated GFR (eGFR) of each patient and NKF/KDOQI classification system to classify the stage of CKD [Citation6]. Demographic details of the patients, preoperative serum creatinine (1 day prior to surgery), preoperative eGFR, pre-PCNL haematocrit, stone complexity as per Guy’s stone score (GSS) [Citation7], and preoperative haemodialysis session were recorded. All the patients were evaluated with USG KUB and NCCT KUB.
Prophylactic antibiotics were administered 1 hour before surgery and continued for 24 hours post-operatively. Nephrology consultation was sought to optimize patients preoperatively, and renal replacement therapy was administered as advised. The surgical procedures were conducted by experienced consultant urologists under spinal anesthesia. Following anesthesia induction, patients were positioned in lithotomy. A 5 Fr open-ended ureteric catheter was placed on the operative side with cystoscopic guidance. Subsequently, the position was changed to the prone position. Radio-opaque contrast was used under fluoroscopic guidance to delineate the pelvicalyceal anatomy. Puncture was performed using either the triangulation or bull’s-eye technique, followed by dilation using Amplatz dilators up to 18Fr. Karl Storz 12Fr rigid nephroscope was utilized for the procedures. Lithotripsy was carried out using the EMS Swiss pneumatic Lithoclast 2. Once the maximum clearance was achieved (evaluated visually and under fluoroscopy), a 4.7Fr/26 cm DJ stent was inserted in an antegrade manner under fluoroscopic guidance. If deemed necessary, a nephrostomy tube was placed.
Operative time was recorded as the time from induction of anaesthesia to placement of DJ stent. Number of punctures, site of puncture (supracostal vs infracostal), placement of percutaneous nephrostomy(PCN), and clearance of stone were recorded for each patient. X-Ray KUB/USG KUB was done on postoperative day 1 to document stone clearance. Nephrostomy tube removal was decided on the basis of nephrostomy tube output and clearance of stones. All the patient were discharged after removing the indwelling catheter. Complete stone clearance was defined as absence of residual calculus or clinically insignificant residual fragment ≤3 mm on postoperative day 1 imaging. Complications were recorded as per the modified Clavien-Dindo (CD) classification of postoperative complications [Citation8].
Stent removal was done at 3 weeks from the day of surgery. Patients were followed up at 6 months for measurement of serum creatinine and eGFR. Data at 6 months were compared with preoperative data. Any patient who had increase or decrease in GFR level were classified as improved or deteriorated, respectively. Patients who continue to be in the same stage were classified as stable. Subgroup analysis was done by dividing the patients in two groups.
Group 1 – included patients with CKD stage 3.
Group 2 – included patients with CKD stage 4 or 5.
Statistical analysis
All the data were entered in MS Excel database. Statistical analysis was done with SPSS software version 22.0. The chi-square test and student’s t-tests were used for analysis. p-value <0.05 was taken as statistically significant.
Results
A total of 46 patients were included in the study, making up to 48 renal units (2 had bilateral nephrolithiasis, 44 had unilateral nephrolithiasis). Five patients had solitary functioning kidney. Demographic characteristics of the population are given in .
Table 1. Demographic characteristics of patients.
There were 30 male and 16 female patients included in this study. The mean age was 45.33 ± 9.48 years. Patients in Group 2 (mean age was 39.33 years) were younger than patients in Group 1 (mean age was 48.05 years). Twenty-four patients (52.1%) had hypertension (HTN), eight patients (17.3%) had Type 2 diabetes mellitus (T2DM), two patients (4.35%) had primary hyperparathyroidism (PHPT) and 2 (4.35%) had hypothyroidism. However, no comorbidities except the stone disease that might cause CKD was noted in 16 patients. There was no statistically significant difference between Group 1 and Group 2 with respect to stone complexity (p = 0.6942).
The mean preoperative creatinine level and preoperative eGFR was 1.91 ± 1.36 mg/dl and 44.97 ± 16.84 ml/min/1.73 m2, respectively. Seven patients (15.2%) required preoperative haemodialysis as advised by nephrologist. Of these two patients were from Group 1 and five patients were from Group 2 (p = 0.003). Two patients in Group 2 required dialysis in the post operative period, while none from Group 1(p = 0.0149).
The mean operative time was 49.08 ± 14.67 minutes. 32 renal units (66.7%) required single puncture while 16 renal units (33.3%) had 2 punctures. A total of 37 renal units required infracostal puncture and 11 renal units required supra-costal puncture. A post-operative nephrostomy tube was put in 8 renal units (16.6%). 43 renal units (89.5%) had complete stone clearance. Two patients (4.3%) required ESWL as auxiliary procedure for residual stones and two patients passed residual fragments spontaneously. The mean hospital stay was 2.1 ± 0.37 days. ()
Table 2. Shows comparison of variables between 2 groups divided on basis of CKD stage.
Follow-up creatinine and eGFR was measured at 6 months. The mean creatinine and eGFR at 6 months was 1.55 ± 1.10 mg/dl and 59.22 ± 25.51 ml/min/1.73 m2, respectively. Overall, there was statistically significant improvement in the eGFR pre-PCNL and post-PCNL at 6 months follow up (p < 0.01). There was improvement in renal function significant enough to cause stage migration to a lower CKD stage in 13 patients(28.2%). 10 patients (29.4%) from CKD stage 3 migrated to stage 2; two patients (25%) from CKD stage 4 were migrated to stage 3, while one patient (25%) migrated from stage 5 to stage 4. 33 patients (71.8%) had stable eGFR who remained in the same stage. Of these 33 patients, 27 patients (58.7%) had improvement in GFR and 6 patients (13.1%) had deterioration in eGFR but not significant enough to cause stage migration at 6 months. The total number of patients with CKD stage 1, 2, 3, 4, and 5 were 0, 10, 26, 7, and 3, respectively, at 6 months follow up ().
Table 3. CKD stage migration in patients after 6 months.
Seven (15.2%) complications were observed in total. On complication stratification as per the CD classification, grade 1 complications was observed in three patients (6.25%) which was treated with antipyretics. Two patients (4.2%) required haemodialysis in post operative period in view of hyperkalaemia.() Two patients (4.2%) developed urosepsis which was managed with fluid resuscitation, vasopressors and antibiotics. The mean preoperative haematocrit was 31.38% and the mean postoperative haematocrit was 30.34% on postoperative day 1, with the mean haematocrit drop of 1.04%, which was statistically insignificant (p = 0.2382). None of the patients required blood transfusion in the post operative period. No mortality was seen in our study. There was no statistically significant difference in complication rates between Group 1 and Group 2 (p = 0.2725).
Table 4. Pre-PCNL and follow up data.
Discussion
Nephrolithiasis causes renal damage because of obstructive uropathy, infection, coexistent medical comorbidities, and frequent surgical intervention [Citation9–11]. Patients with CKD are at increased risk of anaesthetic and surgical complications because of deranged platelet function, increased tendency for bleeding, vulnerable to infection and resultant sepsis, electrolyte imbalances, and fluid overload. Management of CKD patients with nephrolithiasis poses a difficult challenge which requires multidisciplinary approach, including endourologists, nephrologists, cardiologists, endocrinologists, due to multiple associated comorbidities. Preservation of maximum renal function is as important as achieving good stone clearance with minimal postoperative morbidity related to the surgical intervention employed.
The mean age of patients in our study was 45.33 ± 9.48 years, and it is less as compared to studies by Akdeniz et. al [Citation12], Kurien et. al [Citation13], Bilen et. al [Citation14], and Akman et. al [Citation15]. This could be explained by the fact that our region is a stone belt with more number of patients of younger age group and more number of patients undergoing radiological investigation. The mean preoperative creatinine level was 1.91 ± 1.36 mg/dl, comparable to other studies reported in literature [Citation14]. The mean preoperative eGFR was 44.97 ± 16.84 ml/min/1.73 m2, which was similar to other studies like Akman et. al and Akdeniz et. al.
Bilen et. al reported single access in 68.4% of renal units. Our study showed similar results with single puncture required in 66.7% of the renal units, with a mean of 1.33 punctures/renal unit. We were able to manage most of the patients with single access because of added advantage of greater manoeuvrability and easier entrance to whole pelvicalyceal system owing to less diameter of Miniperc nephroscopes. In our study, the mean operative time was 49.08 ± 14.67 minutes which was comparatively less as compared to other studies in literature [Citation14–17]. Complete stone clearance was achieved in 89.5% of renal units which was slightly higher as compared to other studies [Citation12–15]. These findings of our study can be attributed to the fact that all the procedures were performed by experienced senior consultants and less number of renal units had complex stones (35.4% had GSS 3 or 4). Higher CKD stage was associated with lower stone clearance rate with 94.1% of patients in Group 1 and 83.3% in Group 2 had complete stone clearance, however the difference was not statistically significant (p = 0.2543). Tubeless mini-PCNL was done in 38(82.6%) of patients. In view of high clearance rate, lower operative time and use of smaller sheath as compared to standard PCNL, we were able to achieve this high rate of tubeless procedure.
According to EAU 2023 guidelines, PCNL remains the standard surgical method for the treatment of large renal stones currently. The procedure is attended with its related complications. Although the morbidity associated with PCNL is much less as compared to open surgeries, numerous studies in literature have reported a wide range of complications with varying frequencies. Careful preoperative and intraoperative planning may reduce the complications associated with PCNL in this special population. Good communication with the anaesthesiologist should be maintained throughout the procedure, and threshold for considering a staged procedure should be low. Kurien et. al. reported complication rate of 17.1%, Bilen et. al. reported 35.6% complication rate, and Akman et. al. reported complication rate of 15.2% in their study. Majority of the complications are haemorrhage requiring blood transfusion and sepsis, because of the inhibition of cell-mediated immunity and humoral defense mechanisms. In our study, the overall complications rate was 15.2%. None of the patients had significant amount of blood loss requiring blood transfusion. This is mainly due to less punctures required per renal unit, Mini-PCNL technique (smaller tract dilatation(upto 18Fr)). About 6.25% of the total complications were CD grade I complication (fever). About 4.2% was the incidence of urosepsis (Grade 4b) in our study, which was similar to incidence reported in literature of 2.8–9.9% [Citation13–15]. Such a high incidence of sepsis could be due to immunodeficiency in CKD patients, staghorn calculi, matrix stones, and the presence of DJ stent. All of these patients were diabetic, which itself is a risk factor for post procedure septic complications. About 4.2% of the patients required haemodialysis post procedure in view of persistent hyperkalaemia and these patients were CKD stage V preoperatively.
In our study, the mean hospital stay was 2.1 ± 0.37 days, which was much less as compared to reported in literature of 4–7 days [Citation12,Citation13].
The mean creatinine level at 6 months postoperatively was 1.55 ± 1.10 mg/dl. The preoperative mean creatinine level was 1.91 ± 1.36 mg/dl, demonstrating a fall of approximately 0.36 mg/dl which was comparable to result published by Akdeniz et. al. where the fall in mean creatinine level was 0.26 mg/dl at 6 month follow up. The mean eGFR at 6 months was 59.22 ± 25.51 ml/min/1.73 m2. The mean preoperative eGFR was 44.97 ± 16.84 ml/min/1.73 m2. In patients with urolithiasis with bilateral normal kidneys, PCNL has been shown to preserve long term renal function. This benefit should logically extend to patients with CKD. Akman et. al. showed that renal function improved or stabilized in 90% of cases at more than 6 months follow up. Our study results are consistent with this finding and 86.9% of the cases in our study were associated with improvement in eGFR. The use of mini-PCNL technique with smaller diameter sheaths has allowed us to increase the stone free rate and decrease the complications. Kurien et. al. in their study proposed that improvement in eGFR was more in patients with CKD stage 3 as compared to patients with CKD stage 4 or 5. This has reflected in our study too, as 10 patients from CKD stage 3 migrated to CKD stage 2. Two patients migrated from CKD stage 4 to stage 3 and one patient from CKD stage 5 to stage 4. These patients had borderline eGFR who transitioned from stage 4, 5 to higher stage. It might be because these patients already had severe and irreversible kidney damage and hence benefit less likely.
The first mini-PCNL was performed by Jackman using a small access sheath (13Fr) in 1997 [Citation18]. Since then, multiple comparative studies have been done for Mini and Standard PCNL. Li et. al.. published the superiority of mini-PCNL over Standard PCNL with a significantly lesser rate of blood transfusion, higher tubeless procedure rate, lesser hospital stay, and reduced drop in haemoglobin [Citation19]. It has been suggested that because of smaller access sheath in Mini-PCNL, there is increased operative time and subsequently increased absorption of bacterial endotoxins, leading to higher chance of complications. However, studies have shown that the incidence of fever after Mini-PCNL was reduced because Mini-PCNL nephroscope was atleast 6.5Fr smaller compared to sheath [Citation20]. Our study reflects the same with comparable sepsis rate. Operative time is also dependent upon type of energy used for lithotripsy (laser takes more time than pneumatic), stone size and composition, stone burden and complexity. shows a comparative analysis of Standard PCNL with our study and all the benefits of mini-PCNL in otherwise healthy patients with normal kidney function can be translated safely to high risk patients with CKD.
Table 5. Comparison with other studies in literature.
The limitations of this study: this study does not have direct head-to-head comparison of both the techniques (Mini vs Standard PCNL) in CKD patients. Small number of patients (46) with limited follow up of 6 months. A more extended follow up and larger sample size would provide more valuable data. Further studies are required in randomized trial fashion to generate a more concrete data and high level of evidence on this aspect.
Conclusion
PCNL is recommended procedure for nephrolithiasis with acceptable complication rates in CKD patients. With miniaturization of tract size, there is comparable complication rate and better outcome in CKD patients, with improvement in eGFR in these patients post PCNL. An aggressive approach with maximum stone clearance is the best chance to reduce further insult to kidneys and subsequently, renal function deterioration. With proper and efficient multidisciplinary team, high success rate for Mini-PCNL safety and efficacy can be achieved in CKD patients even for complex stones.
Acknowledgments
I acknowledge this entire work to Department of Urology and Kidney Transplant, Sher-I-Kashmir Institute of Medical Sciences(SKIMS).
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
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References
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