The Safety and Efficacy of Percutaneous Nephrolithotomy for Management of Large Renal Stones in Single- Versus Double-Functioning Kidney Patients

Abstract

Purpose:

To demonstrate the safety and efficacy of percutaneous nephrolithotomy (PCNL) for management of large renal stones between single-functioning kidney and double-kidney patients.

Patients and Methods:

Thirty single-functioning kidneys and 30 double-kidney patients with a mean age of 38.5 (±15.6) years in the single group and 42.1 (±14.3) years in the double group (range 11–72 years) underwent PCNL for renal stones larger than 2 cm. The effect of PCNL on global and regional cortical activity was measured using quantitative single-photon emission CT measurement of technetium-99m (^99mTc) dimercaptosuccinic acid (DMSA) scan uptake by the kidneys before and 6 months after PCNL. Variables assessed were stone bulk, size, location, the number of punctures, and anatomic factors. Average hemoglobin and serum creatinine changes, mean operative time, transfusion rate, hospital stay, and different complications were also assessed.

Results:

Mean stone size, mean hospital stay, success rate, and complications were statistically similar in both groups. Mean serum creatinine changes (preoperative and postoperative) were not statistically significant between the two groups (P=0.12). Mean hemoglobin drop (preoperative and postoperative) in both groups was significant, and there was a valuable difference between them (P=0.01). There was a significant difference in the uptake by the treated kidneys before vs after PCNL between both groups statistically (P=0.019), so that the DMSA renal uptake was obviously higher 6 months after PCNL in the double-kidney group compared with its uptake in the single-functioning kidney group.

Conclusion:

^99mTc-DMSA renal scan confirms that renal function was preserved or even often improved after percutaneous stone removal, and the procedure had no detrimental effects on renal function in both groups. There was no statistically significant difference between these groups in terms of morbidity and stone clearance.

Introduction

P ercutaneous nephrolithotomy (PCNL) is performed on a routine basis for the rapid and efficient removal of large renal stones.¹ Despite the enormous clinical knowledge regarding PCNL technique and results, little is known of the impact of PCNL on renal function. Such evaluation sounds difficult because of the presence of a contralateral kidney, which presumably is not injured during treatment and may compensate for damage to the treated side. Studying renal function in patients with a solitary kidney who are undergoing PCNL eliminates the compensatory effects of an untreated contralateral kidney and thus indicates any loss of function in the treated kidney. Furthermore, treatment of patients with a solitary kidney who have large renal stones is a challenging problem in urology.^2,3

To remove the compensatory effect of contralateral kidney, we compared the results and complications of PCNL between patients with a single-functioning kidney and double-kidney patients to assess the efficacy and morbidity of PCNL for management of large renal stones.

Patients and Methods

A total of 60 patients (30 single-functioning kidneys and 30 double-kidney patients) with a mean age of 38.5 (±1 5.6) years in the single group and 42.1 (±14.3) years in the double group (range, 11–72 years) underwent PCNL for renal stones larger than 2 cm. A single-functioning kidney is defined as contralateral renal function less than 15% in split renal function on a technetium-99m (^99mTc) dimercaptosuccinic acid (DMSA) scan preoperatively. Etiology of loss of the contralateral kidney in the single-functioning kidney group consisted of congenital renal agenesis in 3, reflux nephropathy in 5, history of nephrolithotomy and PCNL in 19, radical nephrectomy in 2, and nephrectomy from renal trauma in 1.

Complete blood cell count, serum level of creatinine and hemoglobin (Hgb) were measured in all patients. Preoperative imaging included plain abdominal radiography, ultrasonography, intravenous urography (IVU), and ^99mTc-DMSA scan. In addition to plain abdominal radiography, the serum levels of Hgb and creatinine were checked in the morning of postoperative day 1. Nephrotomography was performed in six cases with nonopaque (2) and semiopaque (4) stones according to the appearance on preoperative IVU and in any case of suspected important residual fragments on radiography of the kidneys, ureters, and bladder on the morning of postoperative day 1.

Meanwhile, to assess the damage of PCNL on the renal cortex in patients undergoing therapy for upper-tract urolithiasis, a ^99mTc-DMSA scan was used as an indicator of renal cortical uptake. Thus, plain abdominal radiography, renal ultrasonography, and ^99mTc-DMSA scan were performed 6 months after the surgery. A nuclear scan on postoperative day 1 may not reflect the pure effects of PCNL on renal function because of the inflammatory events that occurred immediately after the procedure.

Assessed variables were stone bulk, size, location, and anatomic factors. The mean serum level of Hgb and creatinine changes, mean operative time, transfusion rate, hospital stay, and different complications were also assessed. The numbers of punctures were recorded. Stone clearance using PCNL according to stone burden, size, and location was also recorded. Success rate was defined as patients who were stone free or who had asymptomatic, small residual fragments. The cutoff point of 5 mm was used to define the size of insignificant residual fragments.

The effect of PCNL on global and regional cortical activity was measured using quantitative single-photon emission CT (QSPECT) measurement of ^99mTc-DMSA scan uptake by the kidneys before and 6 months after PCNL. Because of the higher percentage of cortical fixation with ^99mTc-DMSA, this agent is the best for renal cortical imaging to show the focal cortical defects or decreased activity (the areas of injury). Statistical analysis was performed by SPSS-17 (Statistical Package for the Social Sciences) software using the paired t test, independent paired t test, chi-square test, and Pearson correlation for comparison of different variables affected by PCNL in single- and double-functioning kidney patients.

Results

Mean stone size was 2.84±0.55 cm for single-functioning kidney patients and 2.91±62 cm for double-kidney patients, which did not show any significant difference (P=0.16). Subclassifications of stones based on their size are also demonstrated in Table 1. Mean Hgb drop (preoperative and postoperative) in both groups was significant, and there was also a valuable difference between them, meaning that the Hgb drop was more prominent in the double-kidney group (P=0.01). Mean serum creatinine changes (preoperative and postoperative) did not indicate any significant change in single-functioning kidney patients, while that was significant for patients with double kidneys; again it was not statistically significant (P=0.21). In terms of mean percent of DMSA renal uptake, there was a significant difference in the uptake by the treated kidneys before vs 6 months after PCNL between both groups. The mean percent of DMSA renal uptake obviously increased 6 months after PCNL in the double-kidney group, while there was no significant difference in DMSA uptake in thesingle-functioning kidney group (preoperative and 6 months postoperative) (Table 2).

Table 1.

Subclassifications of Stones Based on Size in Single-Functioning and Double-Kidney Patients

	Stone size
Groups	2–3 cm	3–5 cm	>5 cm	P value
Single kidney	5 (16.7%)	23 (76.7%)	2 (6.7%)	0.16
Double kidney	4 (13.3%)	19 (63.3%)	7 (23.3%)

Table 2.

Mean Hemoglobin Drop, Creatinine Change, and Mean Percent of Dimercaptosuccinic Acid Renal Uptake (Preoperative And Postoperative) in Single-Functioning and Double-Kidney Groups and Difference in Parameters

Type	Mean (SD)	P value
Single kidney
Hgb preoperative	12.90 (1.18)	< 0.001
Hgb postoperative	11.56 (1.16)
Cr preoperative	1.16 (0.41)	0.111
Cr postoperative	1.71 (0.23)
Split preoperative	89.77 (10.17)	0.35
Split postoperative (6 mos later)	90.61 (9.61)
Double kidney
Hgb preoperative	13.13 (1.55)	< 0.001
Hgb postoperative	11.25 (1.72)
Cr preoperative	1.27 (0.51)	0.004
Cr postoperative	1.39 (0.41)
Split preoperative	39.03 (8.61)	< 0.001
Split postoperative (6 mos later)	43.52 (6.63)
Hgb drop difference
Single kidney	−1.336 (0.58)	0.01
Double kidney	−1.880 (0.95)
Cr change difference
Single kidney	_.5510 (1.85)	0.21
Double kidney	_.1207 (0.21)
Difference of split
Single kidney	0.84 (4.87)	0.019
Double kidney	4.49 (6.72)

SD=standard deviation; Hgb=hemoglobin; Cr=creatinine.

Mean operative time was 96.5±31.2 min and 107±26.1 in single- and double-kidney patients, respectively. There was no significant difference in operative time between these two groups (P=0.752). Mean hospital stay was completely similar (3.36±0.96) days for single-functioning and (3.36±1.33) days for double-kidney patients. The success rate was almost similar in both groups (95.3% for group 1 vs 93.5% for group 2) (P=0.269) (Table 3). Within 6 months of follow-up, patients with residual fragments were closely observed in our clinic, and no one needed re-PCNL over this period. In the single-kidney group, only one patient had significant residual fragments (two particles with diameters of 8 and 7 mm); he underwent shockwave lithotripsy (SWL) and passed the stone fragments during the follow-up period. Two patients in the double-kidney group showed residual fragments larger than 5 mm. One patient had one episode of failed SWL within the period of follow-up, but stone passage occurred in another patient spontaneously.

Table 3.

Mean Success Rate, Mean Hospital Stay, and Operative Time in Single-Functioning and Double-Kidney Patients

Groups		Mean (SD)	P value
Success rate (%)	Single	95.30 (7.30)	0.38
	Double	93.59 (8.63)
Hospital stay (d)	Single	3.36 (0.96)	1.000
	Double	3.36 (1.33)
Operative time (min)	Single	96.5 (31.2)	0.752
	Double	107 (26.1)

SD=standard deviation.

Stone extraction was performed using one access in 25 single-kidney patients and 23 double-kidney patients. The other patients in these two groups underwent PCNL with two accesses. In terms of stone composition, the majority (35 cases) were calcium oxalate dehydrate followed by calcium phosphate in 11, calcium oxalate monohydrate in 8, cystine in 4, and uric acid in 2 cases. There was no significant difference between the two groups in type of stones (P=0.125).

Complications in the single-functioning kidney group consisted of fever in three (10%) patients, urinary leakage in two (6.7%) patients that was managed using ureteral catheter insertion, blood transfusion in one patient, and azotemia in one patient. Complications in the double-kidney group included leakage in seven (23.3%) patients that was managed conservatively in four and by ureteral stent insertion in the other three patients, blood transfusion in one (3.3%) patient, and azotemia in two (6.7%) patients. Complications occurred with a similar rate in both groups (P=0.17) (Table 4 reveals the distribution of different compilations in these two groups according to the Clavien-Dindo classification of surgical complications).⁴

Table 4.

Complication Rate of Percutaneous Nephrolithotomy in Single-Functioning and Double-Kidney Patients According to the Clavien-Dindo Classification of Surgical Complications

Grade of complication	Single kidney	Double kidney
Grade I	1	6
Grade II	3	1
Grade III	2	3
Grade IV	1	0
Grade V	0	0

Discussion

The treatment of patients with large renal calculi has been revolutionized in the past two decades, and minimally invasive techniques have largely replaced open surgery. Small upper urinary tract calculi are preferentially managed with extracorporeal SWL, and larger or more complex stones can be removed via percutaneous approaches.⁵

Renal function impairment is a major concern during PCNL, especially with large renal calculi, but it is still controversial. Despite the enormous clinical knowledge regarding the PCNL technique and its results, there are insufficient quantitative data concerning the effect of this procedure on renal function. There is little in the literature regarding the assessment of renal function in patients who have undergone PCNL; thus, performance of such studies is mandatory.

Long-term effects of PCNL on renal function have been evaluated in another study by the assessment of estimated glomerular filtration rate (GFR) during the first few days after PCNL in 94 patients.⁶ Renal GFR decreased immediately after PCNL, reached a nadir 48 hours after operation, and then increased slowly. It seems advisable to avoid factors that can bear a negative influence on renal function during the early postoperative period such as nephrotoxic drugs, contrast agents, SWL, and re-PCNL. Moskovitz and associates^7,8 conducted research to assess the renal function after PCNL with scintigraphy; there was no statistically significant difference in the uptake by the treated kidneys before and after PCNL. The percentage of the injected isotope dose per cubic centimeter of tissue of the treated kidney was not affected. Regarding the percentage of the injected dose per cubic centimeter of the renal tissue, no statistically significant differences were found between the area of the kidney that underwent PCNL and the untreated area of the same kidney. Recently, Unsal and colleagues⁹ evaluated 75 patients who had undergone PCNL by QSPECT of ^99mTc-DMSA examination before and 3 to 6 months after operation. The ^99mTc-DMSA scan revealed that renal function is preserved after PCNL and that nephrostomy tract dilation methods have similar effects on renal function.

Cass et al.,¹⁰ assessed the short-term and long-term effects of PCNL on 17 patients with a solitary kidney and normal serum creatinine level preoperatively. In 12 patients with less than 24-month follow-up periods, there were no changes in the estimated GFR, whereas 5 patients with more than 24-month follow-up periods had an average 8% reduction in the estimated GFR. The study revealed that PCNL may create a clinically insignificant long-term reduction in renal function. Resorlu and coworkers¹¹ demonstrated the changes in renal function after PCNL in 16 patients with staghorn stones in a solitary kidney. During the 1-year study period, no patient progressed to end-stage renal disease, necessitating dialysis. They also demonstrated a significant improvement for serum creatinine and GFR levels before the operation up to a 1-year follow-up period afterward and confirmed that PCNL was not only effective (successfully extracted or fragmented stones in 13 patients), but also it was safe in the in the patient with a solitary kidney and staghorn calculi.

All of the aforementioned studies were performed either in a single kidney or double-functioning kidneys. Although they demonstrated the effect of PCNL in either case, there is no effect on the number of kidneys to assess the effect of this variable. The current study was set up to evaluate the overall safety and efficacy of the percutaneous surgery profile for the management of large renal stones in patients with a single kidney, compared with double kidneys. The result of our study showed that the efficacy, complications, and change in renal function do not depend on the number of functioning kidneys.

According to the American Urological Association, PCNL should be performed as the first line of treatment for staghorn renal calculi, and the combination of PCNL and SWL had an almost similar stone-free rate in comparison with open surgery.¹² The major concern about large or multiple renal stones, especially in the solitary kidney, has been the requirement of several punctures for PCNL, because these punctures cause adverse events and possible irreversible renal function impairment. The omission of the compensatory effect of the contralateral kidney on the single-functioning kidney with large renal stones increased the possibility of morbidity and progression to dialysis. Previously, improvement of GFR as an indicator of renal function was observed after PCNL even in patients with late-stage chronic kidney disease.¹³ A long-term follow-up of 2 years in the patients with a solitary kidney and creatinine level of less than 2 mg/dL who underwent PCNL revealed that the rate of deterioration of renal function was 29%; one patient with a serum creatinine level of more than 3 mg/dL demonstrated stabilization of the renal function.¹⁴ Some stone burden in the aforementioned study was not in the range of large or staghorn.

Our study, by comparing patients with solitary and double kidney harboring large renal stones (>3 cm) and matching the stone size, revealed that the stone clearance rate was acceptable (95.3%) in the single-functioning kidneys, and 6-month follow-up periods showed no noticeable renal function impairment.

Drawbacks of our study consisted of using solely split renal function according to DMSA scan for the assessment of renal function impairment. Perhaps, assessment of GFR as the indicator of renal function modified the results of our study. In addition, we did not exclude the patients with risk factors that may affect renal function, such as hypertension, diabetes, and history of open or PCNL procedures (four patients in the single-kidney group and nine patients in the double-kidney group had a history of operation).

Conclusion

^99mTc-DMSA renal scan confirms that renal function was preserved or even often improved after percutaneous stone removal, and the procedure had no detrimental effects on renal function in both groups. There were no statistically significant differences between the single- and the double-kidney patients in terms of morbidity and stone clearance.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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