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Original Research

Effect of Renal Function Reserve on Results of Percutaneous Nephrolithotomy


1 HSU Izmir Bozyaka Training and Research Hospital, Department of Urology, Izmir, Turkey
2 Dr. Yasar Eryilmaz Dogubayazit State Hospital, Department of Urology, Agri, Turkey 
3 Mustafa Kemalpaşa Central Hospital, Department of Urology, Bursa, Turkey
4 Amasya University Faculty of Medicine, Department of Urology, Amasya, Turkey
 


DOI : 10.33719/yud.2021;16-1-748024
New J Urol. 2021;16(1): 68-73

ABSTRACT

Objective: In this study, we aimed to compare the success and complication rates of percutane- ous nephrolithotomy (PCNL) according to pre- operative glomerular filtration rates (GFR) of pa- tients who underwent PCNLdue to kidney stones.

Material and Methods: Between January 2012 and December 2016, 794 patients who un- derwent PCNL due to kidney Stones were evalu- ated retrospectively. Preoperative GFR values of patients were calculated according to Cockcroft–Gault formula. The patients with preoperative GFR values>90 ml/min, 60-90 ml/min, 30-60 ml/ min were respectively defined as group-1, group-2 and group-3. Preoperative and perioperative val- ues, Stone free rates and complication rates were compared between the groups. Postoperatively , <4 mm residual stone was identified as success.

Results: There were 466 patients in Group-1, 259 in Group-2 and 67 patients in Group-3. The mean preoperative GFR values of the pa- tients were 118.53 ml/min, 77.76 ml/min and 48.52 ml/min, respectively in group-1, group-2 and group-3 (p <0.001).The mean age of the patients was  62.8±11.47,  51.86±11.10, and60.31±12.7, respectively, in group-1, group-2 and group-3 (p<0.001).The mean Stone burden of the patients were 497.34±518.60 mm2, 517.6±493.8 mm2and 711.06±679.07 mm2, respectively, in group-1, group-2 and group-3 (p=0.013). The number of patients identified with success after surgery was 355 (86.2%), 195 (76.1%) and 50 (74.6%) in group-1, group-2 and group-3, respective- ly (p = 0.542). The number of patients who develop complications was 114 (%24.65), 57 (%22) and 11 (%16.4) in group-1, group-2 and group-3, respectively (p=0.310).

Conclusion: Preoperative GFR valuesare not lonely sufficient to predict success and complications after PCNL.

Keywords: Percutaneous nephrolithotomy, renal function, renal stone, glomerular filtration rates


ABSTRACT

Objective: In this study, we aimed to compare the success and complication rates of percutane- ous nephrolithotomy (PCNL) according to pre- operative glomerular filtration rates (GFR) of pa- tients who underwent PCNLdue to kidney stones.

Material and Methods: Between January 2012 and December 2016, 794 patients who un- derwent PCNL due to kidney Stones were evalu- ated retrospectively. Preoperative GFR values of patients were calculated according to Cockcroft–Gault formula. The patients with preoperative GFR values>90 ml/min, 60-90 ml/min, 30-60 ml/ min were respectively defined as group-1, group-2 and group-3. Preoperative and perioperative val- ues, Stone free rates and complication rates were compared between the groups. Postoperatively , <4 mm residual stone was identified as success.

Results: There were 466 patients in Group-1, 259 in Group-2 and 67 patients in Group-3. The mean preoperative GFR values of the pa- tients were 118.53 ml/min, 77.76 ml/min and 48.52 ml/min, respectively in group-1, group-2 and group-3 (p <0.001).The mean age of the patients was  62.8±11.47,  51.86±11.10, and60.31±12.7, respectively, in group-1, group-2 and group-3 (p<0.001).The mean Stone burden of the patients were 497.34±518.60 mm2, 517.6±493.8 mm2and 711.06±679.07 mm2, respectively, in group-1, group-2 and group-3 (p=0.013). The number of patients identified with success after surgery was 355 (86.2%), 195 (76.1%) and 50 (74.6%) in group-1, group-2 and group-3, respective- ly (p = 0.542). The number of patients who develop complications was 114 (%24.65), 57 (%22) and 11 (%16.4) in group-1, group-2 and group-3, respectively (p=0.310).

Conclusion: Preoperative GFR valuesare not lonely sufficient to predict success and complications after PCNL.

Keywords: Percutaneous nephrolithotomy, renal function, renal stone, glomerular filtration rates

INTRODUCTION

The incidence of adult kidney stones is increasing all over the world day by day. The prevalence of stone disease is between 2% and 20% in the world. Urinary stone disease causes varying degrees of damage to the kidney due to infection and obstruction. However, it is known that chronic diseases such as hypertension, diabetes and metabolic syndrome have effects on stone formation (1). Therefore, urinary system stone disease with renal failure is often encountered together today. The prevalence of chronic kidney failure with kidney stones is known as 17% (2).
Successful treatment of kidney stones with mini- mally invasive methods such as extracorporeal shock wave lithotripsy (SWL) and percutaneous nephrolitho- tomy (PCNL) has reduced the rates of open surgery by up to 3%.In the presence of stones larger than 2 cm thatcannot be treatedwith SWL treatment or are not suitable for this treatment, PCNL is recommended as the first-line treatment (3). The success rates of PCNL vary between 51% and 100% in various studies and complication rates were reported at rates ranging from 0% to 38% (4).

The prevalence of chronic kidney disease (CKD) in surgical patients is increasing in accordance with the aging of the population. Today, these patients can be referred to surgery due to the possibility of surgery with less invasive surgical techniques (5). Chronic kidney disease has been shown to be associated with cardiovascular mortality and morbidity in surgical pa- tients and the normal population (6). In addition, CKD is a chronic disease that increases the risk of complica- tions that may occur due to anesthesia as well as the risk of complications that may occur after surgery.
 
Even small increases in serum creatinine levels after major surgical procedures have been strongly associat- ed with cardiorespiratory, infectious and hemorrhagic complications. (7).

In this study, we aimed to evaluate how the pre-op GFR values affect the operation results of patients who undergo PCNL surgery.


INTRODUCTION

The incidence of adult kidney stones is increasing all over the world day by day. The prevalence of stone disease is between 2% and 20% in the world. Urinary stone disease causes varying degrees of damage to the kidney due to infection and obstruction. However, it is known that chronic diseases such as hypertension, diabetes and metabolic syndrome have effects on stone formation (1). Therefore, urinary system stone disease with renal failure is often encountered together today. The prevalence of chronic kidney failure with kidney stones is known as 17% (2).
Successful treatment of kidney stones with mini- mally invasive methods such as extracorporeal shock wave lithotripsy (SWL) and percutaneous nephrolitho- tomy (PCNL) has reduced the rates of open surgery by up to 3%.In the presence of stones larger than 2 cm thatcannot be treatedwith SWL treatment or are not suitable for this treatment, PCNL is recommended as the first-line treatment (3). The success rates of PCNL vary between 51% and 100% in various studies and complication rates were reported at rates ranging from 0% to 38% (4).

The prevalence of chronic kidney disease (CKD) in surgical patients is increasing in accordance with the aging of the population. Today, these patients can be referred to surgery due to the possibility of surgery with less invasive surgical techniques (5). Chronic kidney disease has been shown to be associated with cardiovascular mortality and morbidity in surgical pa- tients and the normal population (6). In addition, CKD is a chronic disease that increases the risk of complica- tions that may occur due to anesthesia as well as the risk of complications that may occur after surgery.
 
Even small increases in serum creatinine levels after major surgical procedures have been strongly associat- ed with cardiorespiratory, infectious and hemorrhagic complications. (7).

In this study, we aimed to evaluate how the pre-op GFR values affect the operation results of patients who undergo PCNL surgery.

MATERIAL AND METHODS

Study Design
Between January 2012 and November 2016, 794 patients who underwent PCNL due to kidney stonesin a single center were retrospectively analyzed. The data were driven from the electronic medical records of the patients. Patients with bleeding diathesis, patients who were Gfr < 30 and operation data were not available as they were excluded from the study. Preoperative creat- inine clearance of all patients was calculated according to Cockcroft–Gault formula (8). Patients were defined as group-1 with preoperative GFR values> 90 ml/min, group-2 with 60-90 ml/min, and as group-3 with 30-60 ml/min.

Operation Technique
After general anesthesia, a 5 or 6 F ureteral cath- eter was inserted and fixed to a Foley catheter. PCNL was performed in prone position. Access was obtained under fluoroscopy using an 18-gauge needle, and tract was dilated with Amplatz dilatators to 30 F caliber. Stone fragmentation was accomplished using a pneu- matic lithotripter (Vibrolith; Elmed, Ankara, Turkey). At the end of the procedure, 14 F nephrostomy tube was inserted, and antegrade pyelography was per- formed.

Postoperative Follow-up
Demographic information (age, gender, body mass index (BMI)) and perioperative data of the patients were recorded after surgery. Perioperative data were the operation side such as stone burden, number of access, duration of the operation, the length of hospital stay and amount of blood loss. In addition, complications were classified according to the Clavien scoring sys- tem. Postoperative pain was controlled with narcotic analgesics and nephrotoxic drugs which were not giv- en to patients in the perioperative period. Ceftriaxone treatment was given to patients as prophylaxis. Ceftri- axone treatment was discontinued when postoperative nephrostomy tube was taken.
Perioperative values stone-free rates and complication rates were compared between the groups. In the case of stone-free and ≤4 mm stone remaining, the operation was described as successful.Also, postoperative complications were noted according to the Clavien scoring system (9).

Statistical Analysis
Data were analyzed using the Statistical Package for Social Sciences, version 20.0 (SPSS, Chicago, Ill) software program. The Kruskal-Wallis test and Pear- son Chi-square test analyses were used to compare the groups. Data are given as mean ± SD. However, results of analysis are given as median data. Statistical signifi- cance was defined as p<0.05.


MATERIAL AND METHODS

Study Design
Between January 2012 and November 2016, 794 patients who underwent PCNL due to kidney stonesin a single center were retrospectively analyzed. The data were driven from the electronic medical records of the patients. Patients with bleeding diathesis, patients who were Gfr < 30 and operation data were not available as they were excluded from the study. Preoperative creat- inine clearance of all patients was calculated according to Cockcroft–Gault formula (8). Patients were defined as group-1 with preoperative GFR values> 90 ml/min, group-2 with 60-90 ml/min, and as group-3 with 30-60 ml/min.

Operation Technique
After general anesthesia, a 5 or 6 F ureteral cath- eter was inserted and fixed to a Foley catheter. PCNL was performed in prone position. Access was obtained under fluoroscopy using an 18-gauge needle, and tract was dilated with Amplatz dilatators to 30 F caliber. Stone fragmentation was accomplished using a pneu- matic lithotripter (Vibrolith; Elmed, Ankara, Turkey). At the end of the procedure, 14 F nephrostomy tube was inserted, and antegrade pyelography was per- formed.

Postoperative Follow-up
Demographic information (age, gender, body mass index (BMI)) and perioperative data of the patients were recorded after surgery. Perioperative data were the operation side such as stone burden, number of access, duration of the operation, the length of hospital stay and amount of blood loss. In addition, complications were classified according to the Clavien scoring sys- tem. Postoperative pain was controlled with narcotic analgesics and nephrotoxic drugs which were not giv- en to patients in the perioperative period. Ceftriaxone treatment was given to patients as prophylaxis. Ceftri- axone treatment was discontinued when postoperative nephrostomy tube was taken.
Perioperative values stone-free rates and complication rates were compared between the groups. In the case of stone-free and ≤4 mm stone remaining, the operation was described as successful.Also, postoperative complications were noted according to the Clavien scoring system (9).

Statistical Analysis
Data were analyzed using the Statistical Package for Social Sciences, version 20.0 (SPSS, Chicago, Ill) software program. The Kruskal-Wallis test and Pear- son Chi-square test analyses were used to compare the groups. Data are given as mean ± SD. However, results of analysis are given as median data. Statistical signifi- cance was defined as p<0.05.

RESULTS

A total of 792 patients who underwent PCNL due to kidney stones were included in the study. Of these patients, 466 were in group-1, 259 were in group-2 and 67 were in group-3. The mean preoperative GFR values of the patients were 118.537 ml/min, 77.76 ml/min and 48.52 ml/min in Group-1, group-2 and group-3 respec- tively (p<0.001).The mean ages of the patients were 43.48±11.47, 51.86±11.10 and 60.31±12.7 in group-1, group-2 and group-3 respectively (p<0.001). The mean body mass indices of the patients were 27.35±4.54, 25.35±4.26 and 25.39±4.29 kg/m2 in Group-1, Group-2 and Group-3, respectively (p<0.001)(Table 1). The number of patients with bleeding over 250 ml was 183 (39.3%), 92 (35.5%) and 22 (32.8%) in group-1, group-3, respectively. There were no statistically significiant differences. The number of patients with resid- ual stones was 111 (23.8%), 62 (23.9%) and 17 (25.4%) in group-1, group-2 and group-3, respectively (Table 2). There were no statistically significiant differences. The number of patients without complications was 352

Table 2. Perioperative Data of Patients
 
(75.6%), 202 (78%) and 56 (83.6%) in group-1, group-2 and group-3, respectively (Table 3). There were no sta- tistically significant differences between the groups in terms of complication development. The developing complications are shown in Table 3 in detail.


RESULTS

A total of 792 patients who underwent PCNL due to kidney stones were included in the study. Of these patients, 466 were in group-1, 259 were in group-2 and 67 were in group-3. The mean preoperative GFR values of the patients were 118.537 ml/min, 77.76 ml/min and 48.52 ml/min in Group-1, group-2 and group-3 respec- tively (p<0.001).The mean ages of the patients were 43.48±11.47, 51.86±11.10 and 60.31±12.7 in group-1, group-2 and group-3 respectively (p<0.001). The mean body mass indices of the patients were 27.35±4.54, 25.35±4.26 and 25.39±4.29 kg/m2 in Group-1, Group-2 and Group-3, respectively (p<0.001)(Table 1). The number of patients with bleeding over 250 ml was 183 (39.3%), 92 (35.5%) and 22 (32.8%) in group-1, group-3, respectively. There were no statistically significiant differences. The number of patients with resid- ual stones was 111 (23.8%), 62 (23.9%) and 17 (25.4%) in group-1, group-2 and group-3, respectively (Table 2). There were no statistically significiant differences. The number of patients without complications was 352

Table 2. Perioperative Data of Patients
 
(75.6%), 202 (78%) and 56 (83.6%) in group-1, group-2 and group-3, respectively (Table 3). There were no sta- tistically significant differences between the groups in terms of complication development. The developing complications are shown in Table 3 in detail.

DISCUSSION

Renal function decreases with aging and is also close- ly related to chronic diseases that lead to poor perioper- ative outcomes, such as diabetes mellitus, dyslipidemia and hypertension. Chronic kidney disease (CKD) is de- fined as the estimated GFR<60cc /min/1.73m2 and has been associated with an increase in all-cause deaths and especially cardiovascular deaths (10). Chronic kidney disease (CKD) significantly increases the risk of death, cardiovascular disease and hospitalization of adult pa- tients (11).In our study, no deaths were reported.Dura- tion of hospital stay was higher in group-3 compared to other groups but there was no statistical difference be- tween the groups. We attribute the longer hospital stay in this group-3 to our desire to follow up more stringent GFR.

Various serious complications may occur in patients with impaired renal function, such as disruption of drug metabolism and excretion, edema in tissues as a result of impaired water-electrolyte balance, delay in wound healing and difficulties in infection control (12,13). It has also been reported that immune deficiency is com- mon in patients with CKD (14).In our study, the num- ber of patients who developed postoperative infection was similar between the groups. Antibiotic therapy was sufficient to control the infection in these patients.

Sairam et al. (15) found that there was a signifi- cant difference between the total complication rates in their articles comparing patients with CKD 0-2 and 4-5. (18.5% vs. 33.8%) p<0.001.In the article by Kilinc et al. (16) comparing the diagnostic RIRS (Retrograde intrarenal surgery) results of patients with chronic he- modialysis patients and normal kidney function; while there was no statistically significant difference between the overall complication rates (10.5% vs. 4.8%; p=0.16). In our study, complications were classified according to the Clavien-Dindo classification system. We found no statistical significiant difference between the complica- tion rates of both total and subgroups.
Seitz et al. (17) reported there were 7% blood trans- fusion requirement in patients with normal kidney function during PCNL operation. In a review, Jones et al. (18) investigated the efficacy and safety of PCNL in CKD patients, the need for transfusion was 20%. This rate increase was associated with high preoperative anemia prevalence and presence of platelet dysfunction in CKD patients.In the CROES study, when they com- pared the transfusion requirement ratio in patients with Level 4/5 to those with Level 3 CKD, they found 18.4% and 6.1%, respectively. They also found statistically sig- nificant difference among these ratios (p<0.001) (19). In our study, we evaluated the mean amount of bleed- ing, not the transfusion rate, because the preoperative hemogram values of all patients were not at the same rate. We found no statistical significiant difference be- tween the groups when the amounts of bleeding were compared.

In the CROES study, the stone-free rates were 71.2% in patients with stage 4-5 CKD and 76.9% in patients with stage 0-2 CKD (15). Yuruk et al. (20) compared the patients with CKD stage 4-5 and patients with normal kidney function with RIRS due to kidney stones. The third month stone-free rates were 87.1% and 86.2%, respectively (p=0.75).Srivastava et al. (221) investigat- ed SWL results in patients with GFR <30 ml / min and reported that retreatment requirement was 84.4% and stone-free rates were 34.4%. In our study, stone-free rates were similar among the groups (p=0.542).Stone- free rates in our study were also similar to other studies (74.6-76.2%), and there was no statistically significant difference between the groups.

The main limitations of the current study are its ret- rospective design which could possibly cause some bias, and using serum creatinin evalueto calculate GFR may not be the best method. TheCockcroft–Gault formula is a widely used and shows GFR changes with appropriate error.However, the aim of our study was not to define the most accurate GFR measurement. We use GFR only for preoperative classification. So, we think that the Cockcroft–Gaultformula will not cause significant er- rors in terms of the results. Our study has some poten- tial advantages. Firstly, the same surgeons performed PCNL in our clinic with the same protocol so there was no surgery-effect bias.


DISCUSSION

Renal function decreases with aging and is also close- ly related to chronic diseases that lead to poor perioper- ative outcomes, such as diabetes mellitus, dyslipidemia and hypertension. Chronic kidney disease (CKD) is de- fined as the estimated GFR<60cc /min/1.73m2 and has been associated with an increase in all-cause deaths and especially cardiovascular deaths (10). Chronic kidney disease (CKD) significantly increases the risk of death, cardiovascular disease and hospitalization of adult pa- tients (11).In our study, no deaths were reported.Dura- tion of hospital stay was higher in group-3 compared to other groups but there was no statistical difference be- tween the groups. We attribute the longer hospital stay in this group-3 to our desire to follow up more stringent GFR.

Various serious complications may occur in patients with impaired renal function, such as disruption of drug metabolism and excretion, edema in tissues as a result of impaired water-electrolyte balance, delay in wound healing and difficulties in infection control (12,13). It has also been reported that immune deficiency is com- mon in patients with CKD (14).In our study, the num- ber of patients who developed postoperative infection was similar between the groups. Antibiotic therapy was sufficient to control the infection in these patients.

Sairam et al. (15) found that there was a signifi- cant difference between the total complication rates in their articles comparing patients with CKD 0-2 and 4-5. (18.5% vs. 33.8%) p<0.001.In the article by Kilinc et al. (16) comparing the diagnostic RIRS (Retrograde intrarenal surgery) results of patients with chronic he- modialysis patients and normal kidney function; while there was no statistically significant difference between the overall complication rates (10.5% vs. 4.8%; p=0.16). In our study, complications were classified according to the Clavien-Dindo classification system. We found no statistical significiant difference between the complica- tion rates of both total and subgroups.
Seitz et al. (17) reported there were 7% blood trans- fusion requirement in patients with normal kidney function during PCNL operation. In a review, Jones et al. (18) investigated the efficacy and safety of PCNL in CKD patients, the need for transfusion was 20%. This rate increase was associated with high preoperative anemia prevalence and presence of platelet dysfunction in CKD patients.In the CROES study, when they com- pared the transfusion requirement ratio in patients with Level 4/5 to those with Level 3 CKD, they found 18.4% and 6.1%, respectively. They also found statistically sig- nificant difference among these ratios (p<0.001) (19). In our study, we evaluated the mean amount of bleed- ing, not the transfusion rate, because the preoperative hemogram values of all patients were not at the same rate. We found no statistical significiant difference be- tween the groups when the amounts of bleeding were compared.

In the CROES study, the stone-free rates were 71.2% in patients with stage 4-5 CKD and 76.9% in patients with stage 0-2 CKD (15). Yuruk et al. (20) compared the patients with CKD stage 4-5 and patients with normal kidney function with RIRS due to kidney stones. The third month stone-free rates were 87.1% and 86.2%, respectively (p=0.75).Srivastava et al. (221) investigat- ed SWL results in patients with GFR <30 ml / min and reported that retreatment requirement was 84.4% and stone-free rates were 34.4%. In our study, stone-free rates were similar among the groups (p=0.542).Stone- free rates in our study were also similar to other studies (74.6-76.2%), and there was no statistically significant difference between the groups.

The main limitations of the current study are its ret- rospective design which could possibly cause some bias, and using serum creatinin evalueto calculate GFR may not be the best method. TheCockcroft–Gault formula is a widely used and shows GFR changes with appropriate error.However, the aim of our study was not to define the most accurate GFR measurement. We use GFR only for preoperative classification. So, we think that the Cockcroft–Gaultformula will not cause significant er- rors in terms of the results. Our study has some poten- tial advantages. Firstly, the same surgeons performed PCNL in our clinic with the same protocol so there was no surgery-effect bias.

CONCLUSION

The success and complication rates of the operation depend on multiple variables. GFR is only one of these multiple variables which does not lonely affect success and complications in PCNL operation.

Conflict of Interest
All authors declared that there is no conflict of in- terest.

Financial Disclosure
None.

Ethical Approval
This study was conducted retrospectively. The study protocol conformed to the ethical guidelines of the Helsinki Declaration.


CONCLUSION

The success and complication rates of the operation depend on multiple variables. GFR is only one of these multiple variables which does not lonely affect success and complications in PCNL operation.

Conflict of Interest
All authors declared that there is no conflict of in- terest.

Financial Disclosure
None.

Ethical Approval
This study was conducted retrospectively. The study protocol conformed to the ethical guidelines of the Helsinki Declaration.

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