Propensity Score-Matched Analysis Comparing Retrograde Intrarenal Surgery with Percutaneous Nephrolithotomy for Large Stones in Patients with a Solitary Kidney

Abstract

Purpose:

To evaluate the clinical efficacy, safety, and cost of retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PCNL) in the treatment for large renal stones in patients with a solitary kidney.

Patients and Methods:

In this study, 117 patients with a solitary kidney who had undergone PCNL or RIRS for renal stones larger than 2 cm between January 2010 and December 2016 were retrospectively evaluated. The patients' demographic data, clinical characteristics, and perioperative outcomes were collected through a review of their medical records. Forty-three patients treated with PCNL were compared to 43 patients treated with RIRS by propensity score-matched analysis. The stone-free rate, retreatment rate, complication rate, and efficacy quotient (EQ) were assessed in both groups.

Results:

Initial stone-free rate of the PCNL group after a single procedure was significantly higher compared with the RIRS group (74.42% vs 34.88%, p < 0.001), whereas there was no significant difference in the final stone-free rate after repeated procedures (90.70% vs 88.37%, p = 0.713). PCNL had a significantly lower retreatment rate than RIRS (16.28% vs 63.79%, p < 0.001), and the PCNL group underwent fewer procedures than the RIRS group (p < 0.001). Thus, PCNL group had a higher EQ (78.00% vs 53.52%). Although cost per procedure of PCNL was significantly higher compared with RIRS (p < 0.001), the total costs were comparable. Complication rate of RIRS was lower compared with PCNL with no statistical significance (p = 0.193), and acute kidney injury rates were also comparable (PCNL vs RIRS: 13.95% vs 6.98%, p = 0.533).

Conclusions:

With fewer repeated surgical procedures, higher EQ, and comparable total costs, PCNL is recommended as the first choice for the treatment of large renal calculi in patients with a solitary kidney. As for specific indications such as anticoagulant drugs, RIRS is a safer choice with fewer complications and acceptable final stone-free rate.

Introduction

In the management of large intrarenal calculi (>2 cm in diameter), percutaneous nephrolithotomy (PCNL) is recommended as first-line treatment.¹ Even though it yields a high stone clearance rate, the intervention is associated with a high risk of severe complications such as renal injury or bleeding.² For patients with a solitary kidney, uncontrollable renal hemorrhage may lead to disastrous events. In special cases that PCNL is not an option, retrograde intrarenal surgery (RIRS) has also been reported to yield an increasingly high stone clearance rate with few complications.^3,4 However, when treating large renal stones, RIRS may require follow-up procedures to achieve a complete removal of stones,⁵ which posed patients with increasing surgical and anesthetic risks. To our knowledge, the comparison of PCNL and RIRS in treatment of large stones in a solitary kidney has been rarely reported, and there has been no study ever assessing the efficacy quotient (EQ) of RIRS and PCNL. In this study, we compared the two procedures in aspects of EQ, safety, and costs for this special population.

Patients and Methods

Study design and data collection

The study retrospectively investigated all consecutive patients diagnosed with a solitary kidney through the electronic medical record system and radiological database, who underwent PCNL or RIRS in Changhai Hospital between January 2010 and December 2016. The institutional review board approved the study protocol. Informed consent was obtained from all patients before operation. Solitary kidney is identified as patients with either anatomical or functional solitary kidney. Anatomical solitary kidney included congenital renal agenesis and unilateral nephrectomy. Functional solitary kidney is defined as patients whose preoperative evaluation showed a contralateral kidney function is <5% in split renal function on a 99m Tc labeled dimercaptosuccinic acid single-photon emission computed tomography or CT showed the contralateral kidney was significantly atrophic, and intravenous pyelography showed no urine secretion.

Data regarding the following parameters were collected: age, gender, body mass index (BMI), stone characteristics, operation time, perioperative outcomes and complications, and the incidence of postoperative acute renal injury. The choice of the treatment modality in each case was made on the basis of comorbidities, anatomy of the renal collecting system, and patients' preference. Patients receiving anticoagulant therapy, or renal abnormalities and potential renal or colon tumor that may affect percutaneous puncture were contradicted to PCNL and received RIRS surgery. Cumulative stone diameter (CSD) and stone burden were evaluated by a radiologist (X.L.) and an experienced urologist (X.S.) based on helical noncontrast CT scan and kidney, ureter, and bladder radiograph (KUB) plain film. CSD was calculated by summing up the maximum diameters in the cases of multiple stones, and stone burden was calculated as the sum of the areas of all stones using the following formula: Stone area per stone = Length × Width × π × 1/4. Costs were acquired through the accounting system, including surgery cost, anesthesia, pharmaceutical, medical and nursing costs, and costs for hospital stay. Matching criteria were age, gender, BMI, and stone characteristics, including CSD, stone burden, and stone numbers.^6,7

PCNL technique

The point of percutaneous access was identified under ultrasonographic guidance as descried before,⁸ and 22F to 24F Amplatz working sheaths were inserted to dilate the percutaneous tract to allow insertion of the scope. A 17F nephroscope (Karl Storz, Tuttlingen, Germany) and a 1000-μm holmium laser fiber (VersaPulse^®100 W PowerSuite™; Coherent Medical Group, Santa Clara, CA) were advanced into the kidney, and lithotripsy was performed at a laser power of 3.5J and a pulse frequency of 20 Hz. Stones were completely fragmented and flushed out by irrigation. At the end of the lithotripsy, a 6F or 7F Double-J stent and an 18F to 20F nephrostomy tube were placed in situ for drainage.⁸ The tube was removed 2 to 4 days after the operation, on condition that there was no complication or the nephrostomy tube is draining clear urine.

RIRS technique

For the RIRS procedure, a ureteral access sheath (UAS) (inner diameter: 9.5F or 12F; outer diameter: 11.5F or 14F; Cook Medical, Bloomington, IN) was advanced into the kidney directed by the guidewire. Subsequently, a 7.5F flexible ureteroscope (Storz FLEX-X2; Karl Storz) was inserted to inspect the pelvicaliceal system and identify the locations of the stones. Lithotripsy was then performed by a 200-μm holmium laser fiber setting at an energy level of 0.4 to 1.0J and pulse rate of 10 to 30 Hz. The resultant stone fragments were retrieved by using a 2.4F zero-tipped nitinol stone basket (Cook Medical). Complete fragmentation of the identified stones after lithotripsy was confirmed by repeated inspection of the collecting system. The procedure ended up with a Double-J stent left in situ to allow for drainage. A KUB was obtained on the first postoperative day and 1 month after the surgery. If a large burden of residual stones was detected, the procedure was repeated until the patient achieved a stone-free status. The Double-J stent was removed under local anesthesia.

Perioperative outcome assessment

The operation time was calculated as starting from introducing the scope into the urethra for RIRS and from establishing a renal access for PCNL, respectively, to the placement of the Double-J stent. Stone-free status were assessed by ultrasonography and KUB radiograph and/or CT, and was defined as complete absence of residual fragments or presence of residual fragments of diameter <2 mm. The EQ was calculated using the following equation as previously described⁹: EQ = [Stone-free rate/(100% + Retreatment rate + Auxiliary procedure rate)]*100%. For each patient, acute kidney injury (AKI) was defined according to Kidney Disease Improving Global Outcomes (KDIGO) AKI.¹⁰

Statistical analysis

The intergroup comparisons of continuous variables were made using Student's t-test, nonparametric test, and one-way analysis of variance tests, whereas those for categorical variables were made using the chi-square or Fisher's exact test. Categorical variables were denoted as the frequency and percentage, and continuous variables were denoted as the median and interquartile range. A p-value <0.05 was considered statistically significant. Statistical analysis was performed using the software SPSS, Inc. Released 2008, SPSS Statistics for Windows, Version 17.0 (SPSS, Inc., Chicago, IL). The propensity score was estimated for all the patients by binary logistic regression, with the age, gender, BMI, stone CSD, stone burden, and single or multiple stones as the dependent variable. The covariates were the same as the nonpropensity score analysis. Analysis was performed using SAS software (SAS, Inc.) for a case–control match on propensity score.

Results

Clinical characteristics of patients

A total of 117 consecutive patients with a solitary kidney undergoing RIRS and PCNL (67 vs 50) were enrolled into our study. Forty-three patients treated with PCNL were matched to 43 patients with RIRS. The two treatment groups were comparable in terms of baseline demographic characteristics and etiology of the solitary kidney (Table 1). Among the patients undergoing RIRS, 31 patients had previous stenting, 1 for the correction of acute urinary obstruction and 30 for passive dilation of the ureter, whereas the remaining 12 patients did not receive any preoperative stenting. The puncture sites in PCNL were 12 in upper calix, 22 in middle calix, 6 in lower calix, and 3 with multiple calices. Cost per procedure of PCNL treatment was significantly higher compared with RIRS ($4154 vs $2691, p < 0.001), whereas the actual total cost of the two interventions was comparable because RIRS was associated with more repeated procedures (range: 1–6) (Table 1).

Table 1.

Demographic and Clinical Data

	RIRS (n = 43)	PCNL (n = 43)	p
Procedures, n (range)	82 (1–6)	49 (1–2)	<0.001
Total cost ($)^a	4692 ± 2279	4569 ± 1744	0.779
Cost per procedure ($)^a	2691 ± 950	4154 ± 1627	<0.001
Mean age (years)^a	51.88 ± 11.12	50.79 ± 14.54	0.696
Gender			1.000
Male	23	23
Female	20	20
BMI (kg/m²)^a	24.06 ± 3.48	24.61 ± 4.60	0.536
Laterality			0.665
Left	21	19
Right	22	24
Comorbidities
HT	15	9	0.149
DM	6	1	0.110
CKD	5	2	0.433
Etiology
Contralateral nephrectomy	8	5	0.366
Congenital renal agenesis	3	4	1.000
Functional solitary kidney	32	34	0.610
Positive preoperative urine culture, n (%)	13 (30.23)	15 (34.88)	0.645
Mean preoperative serum creatinine (mg/dL)^a	1.34 ± 0.76	1.36 ± 0.93	0.943

Values are presented as mean ± standard deviation.

BMI = body mass index; CKD = chronic kidney disease; DM = diabetes mellitus; HT = hypertension; PCNL = percutaneous nephrolithotomy; RIRS = retrograde intrarenal surgery.

Clinical outcomes and complications

The perioperative data are shown in Table 2. The mean operative duration was longer (118.00 minutes vs 86.91 minutes; p < 0.001) and the mean postoperative hospitalization period was longer (6 days vs 2 days, p < 0.001) in the PCNL group than the RIRS group. Although the overall complication rate of the PCNL group was higher (53.49% [23/43] vs 37.21% [16/43], p = 0.193, Table 2), there was no significant difference between the two groups and neither group developed severe (Clavien Grade IV–V) complications. In addition, despite the presence of the postoperative Double-J stent, one patient developed acute urinary obstruction (Clavien Grade III severity) 10 days after RIRS because of Steinstrasse, which led to anuria and acute renal injury; the patient underwent emergency ureterorenoscopy to relieve the obstruction. In this case, the serum creatinine levels returned to the baseline levels after the surgery. In one PCNL case, renal injury and intrarenal bleeding occurred when establishing the percutaneous tract (Clavien Grade II). There was no other way, but to stop the procedure immediately and turn to RIRS after kidney bleeding was alleviated. AKI rates, preoperative and postoperative estimated glomerular filtration rate, were comparable in the two groups.

Table 2.

Perioperative Data, Surgery-Associated Complications by Clavien Scale, and Acute Kidney Injury Grade

	RIRS	PCNL	p
Mean operation duration (minutes)^a	86.91 ± 37.45	118.00 ± 40.11	<0.001
Mean postoperative hospitalization duration (days)^b	2 (1–2)	6 (5–8)	<0.001
Decline in Hb level (g/L)^b	8 (0–13)	8 (1–15)	0.635
Decline in Hct level (%)^b	2.80 (−0.10 to 4.20)	2.50 (0.80–4.50)	0.353
Mean postoperative serum creatinine (mg/dL)^a	1.47 ± 1.10	1.45 ± 0.98	0.084
Clavien-Dindo complications, n (%)
Grade I	11 (25.58)	10 (23.26)
Grade II	4 (9.30)	13 (30.23)
Grade III	1 (2.33)	0
All	16 (37.21)	23 (53.49)	0.193
Complications classification^c
Transient serum creatinine increase (Grade I)	11	10
Renal hemorrhage requiring blood transfusion (Grade II)	0	1
Infection/SIRS/sepsis requiring additional antibiotics (Grade II)	4	12
Anuria/Steinstrasse (Grade III)	1	0
KDIGO AKI, n (%)
Grade I	2 (4.65)	5 (11.63)
Grade II	0	1 (2.33)
Grade III	1 (2.33)	0
All	3 (6.98)	6 (13.95)	0.483
eGFR (mL/minutes/1.73 m²)^b
Preoperation	68.37 (49.22–80.80)	63.73 (47.07–86.89)	0.766
Postoperation	63.90 (45.80–81.62)	58.05 (46.19–81.91)	0.632

Values are presented as mean ± SD;

Values are presented as median (Q1–Q3).

Cases with simultaneous complications.

eGFR = estimated glomerular filtration rate; Hb = hemoglobin; Hct = hematocrit; SD = standard deviation; KDIGO AKI = Kidney Disease Improving Global Outcomes Acute Kidney Injury.

Stone-free rates and EQ in subgroup analysis

As shown in Table 3, the stone burden was 445.38 mm² vs 475.00 mm² in the RIRS and PCNL groups (p = 0.637), and CSD was 37.50 mm vs 39.37 mm (p = 0.459), respectively. In further analysis in subgroups by CSD ≤3 cm, 3 to 4 cm, and >4 cm, there were no significant differences in stone burden among the these groups. And CSD were also comparable in groups of CSD 3 to 4 cm and >4 cm.

Table 3.

Efficacy of Stone Treatment

	RIRS				PCNL
	Total (n = 43)	≤30 mm (n = 11)	30–40 mm (n = 14)	>40 mm (n = 18)	Total (n = 43)	≤30 mm (n = 7)	30–40 mm (n = 19)	>40 mm (n = 17)
CSD^a (mm)	37.50 ± 12.69	20.79 ± 1.90^*	35.34 ± 3.00	49.39 ± 7.40	39.37 ± 10.49	25.04 ± 4.00	34.62 ± 3.06	50.59 ± 4.69
Stone burden^a (mm²)	445.38 ± 288.85	236.78 ± 121.40	370.27 ± 128.24	631.27 ± 339.68	475.00 ± 306.62	238.93 ± 81.68	356.14 ± 108.03	705.23 ± 335.67
Multicaliceal stone, % (n)	53.49 (23)	45.45 (5)	57.14 (8)	55.56 (10)	67.44 (29)	28.57 (2)	84.21 (16)	70.59 (12)
Procedures, n ^b	2 (1–2)^§§§	1 (1–2)	2 (1–2)^§§	2 (1–2)^§§	1 (1–1)	1 (1–1)	1 (1–1)	1 (1–1)
Initial stone-free rate, % (n)	34.88 (15)^###	63.64 (7)	21.43 (3)^##	27.78 (5)^#	74.42 (32)	85.71 (6)	78.95 (15)	64.71 (11)
Final stone-free rate, % (n)	88.37 (38)	90.91 (10)	71.43 (10)^#	100.00 (18)	90.70 (39)	85.71 (6)	100.00 (19)	82.35 (14)
Retreatment rate, % (n)	63.79 (27)^###	36.36 (4)	71.43 (10)^##	66.67 (13)^##	16.28 (7)	0	21.05 (4)	23.53 (4)
Auxiliary procedure rate, % (n)	2.33 (1)	0	7.14 (1)	0	0	0	0	0
EQ, %	53.52	66.67	40.00	58.06	78.00	85.71	82.61	66.67

Values are presented as mean ± SD.

Values are presented as median (Q1–Q3).

p < 0.05, (RIRS vs PCNL) Student's t-test.

p < 0.05, ^§§ p < 0.01, ^§§§ p < 0.001 (RIRS vs PCNL) Mann–Whitney U test.

p < 0.05, ^## p < 0.01, ^### p < 0.001 (RIRS vs PCNL) Pearson chi-square test.

CSD = cumulative stone diameter; EQ = efficacy quotient.

Initial stone-free rate of the PCNL group was higher compared with the RIRS group, whereas there was no significant difference for the final stone-free rate (PCNL vs RIRS initial: 74.42% vs 34.88%, p < 0.001; final: 90.70% vs 88.37%, p = 0.713). Repeated RIRS for elimination of residual stones was required in 27 patients, whereas 6 patients needed a second-look procedure in the PCNL group and 1 patient underwent RIRS after initial PCNL to achieve stone-free status. We further compared stone-free rate, retreatment rate, and EQ in subgroups. Initial stone-free rates of PNCL were higher than RIRS in all subgroups, whereas final stone-free rates were comparable among groups. Retreatment rate following RIRS was higher than PCNL among overall, CSD ≤3 cm, CSD 3 to 4 cm, and CSD >4 cm population (p < 0.001, p = 0.119, p = 0.004, and p = 0.004, respectively). As shown in Table 3, retreatment rate following RIRS was 63.79% and retreatment rate following PCNL was 16.28% in overall population. In general, with high stone-free rates and low retreatment rates, PCNL presented a higher EQ than RIRS.

Discussion

The management of large renal stones in patients with a solitary kidney is rather challenging to achieve maximal stone clearance with low retreatment rate and minimal morbidity. Although PCNL allows for complete removal of large stones, it is associated with high risks of renal replacement for patients with a single functional kidney because of uncontrollable hemorrhage necessitating embolization or nephrectomy.¹¹ In our previous study, RIRS could afford acceptable high success rate and low morbidity rate among solitary kidneys, especially in renal stones <2 cm, but stone-free rates dropped remarkably in large renal stones.¹² However, experience on comparison of the two interventions in large renal stones patients with a solitary kidney is very rare. As far as we know, only two studies compared the stone-free rate and complications of PNCL and RIRS.^13,14 In the first study, the final stone-free rate of RIRS was as low as 43.4%, whereas PCNL was 71.7%.¹³ Nevertheless, the patients of this study underwent minimally invasive PCNL, not standard PCNL for the management of large renal stones, which is widely employed. Stone-free rates were comparable in another study, although stone size and background data presented inevitable biases.¹⁴ One limitation of the two studies is that only stone-free rate and complications were assessed, whereas other factors such as EQ and medical cost that may affect decision-making were not. This study provides data on important issues related to the two interventions' efficacy, safety, and cost comparison in solitary kidney populations.

In a study reported by Atis and colleagues,¹⁵ RIRS treatment for stones in a solitary kidney showed quite high stone-clearance efficacy with the initial and final stone-free rates of 83.3% and 95.8%, respectively. This disparity could be attributed to the large stone burden and multicaliceal stone numbers of this study. However, none of the above studies assessed the EQ before. The majority of studies evaluated the efficacy of interventions with stone-free rate as the main indicator for treatment success, although it is theoretically possible to achieve a 100% stone-free rate by exposing patients to repeated procedures, which is inappropriate as a result of not only the increasing complication risks but also waste of medical resources.¹⁶ However, EQ is a more objective outcome measurement because it takes the stone-free rate into consideration and includes other undesirable outcomes, such as the rates of retreatment and auxiliary procedure that increases patient morbidity. EQ is widely used in extracorporeal shockwave lithotripsy as an indicator of efficiency.¹⁷ In this study, EQ is appropriate in assessing the treatment of large burden stones in a solitary kidney because the intervention is associated with residual stone, stage procedures, and high risk of auxiliary procedure in the presence of severe complications. EQ of RIRS for stones in a solitary kidney is 53.52% compared to 76.47% of PCNL, showing an obvious superiority for PCNL. Pan and colleagues¹⁸ reported that EQs of RIRS and PCNL for anatomically normal renal stone of 2 to 3 cm were 52.3% and 90.4%, which is consistent with our results. Moreover, through subgroup analysis of stone size by 40 mm, we found that EQs of RIRS and PCNL were quite close in the group of stone size larger than 40 mm. For both interventions, stones larger than 40 mm brought in poor initial stone-free rate and required repeated operations.

Although single procedure cost was significantly lower in the RIRS group compared with PCNL, total cost of both interventions was comparable because RIRS was associated with more repeated procedures, which is consistent with the previously mentioned study.¹⁸ Moreover, it is noteworthy that the above medical cost did not include endourological scopes and instrument purchase and maintenance. Considering the high retreatment rate and auxiliary procedures, including Double-J stent removal, RIRS did not present any advantage over the actual medical cost.

Complication is another important issue to be addressed. The analysis comparing RIRS and PCNL yielded complication rates similar to those of ours.^12,13 The process of establishing a percutaneous renal access of PCNL can lead to critical complications,^19,20 such as severe renal bleeding necessitating embolization or even nephrectomy. Bucuras and colleagues reported that the percentage of patients requiring transfusion was significantly larger among patients with a solitary kidney than those with bilateral kidneys (p = 0.014).²¹ One renal bleeding case in this study underwent transfusion and turned to RIRS after the bleeding was controlled. However, complication rate of renal bleeding is rather low in large experienced medical centers.^8,22,23 Therefore, PCNL for large renal stones in solitary kidney should be prudently chosen and conducted in experienced centers because of the impending risk of hemorrhage. However, the risk of hemorrhagic complications requiring blood transfusion is also associated with a large tract size.²⁴ We routinely used 22F to 24F percutaneous sheath, which could decrease the risk of bleeding and the need for blood transfusion.

Urosepsis is a serious complication following PCNL or RIRS. Usually we performed antibiotic prophylaxis for all patients with second-generation cephalosporins. If a urine culture result was positive, we would use a sensitive drug to the urine culture result until the repeat urine culture was negative. In this study, infection-related complication, including urinary infection, SIRS, and sepsis requiring additional antibiotics, developed in 4 patients following RIRS and in 12 patients following PCNL (9.3% vs 27.9%). The incidence of infectious complications following RIRS ranged between 1.7% and 18.8%.^25,26 The incidence of fever following PCNL ranged from 0% to 32.1%.²³ Operative duration, infectious stones, and great comorbidities were related to infectious complications following RIRS.^25,27 Large stone burden, increased operation time, and positive urine culture were risk factors of infection-related complications after PCNL.^28
–30 Our study controlled stone burden for the two groups, and comorbidities and positive urine culture of the two groups were comparable. Also, the operative time was longer in PCNL than RIRS, which may be an important cause of high infection complication rate.

RIRS is often unable to achieve instant stone clearance at the end of surgery and needs postoperative spontaneous expulsion, which increases risks of ureteral obstruction or Steinstrasse for solitary kidney patients. Unlike the case with PCNL in which stone fragments can be removed through the established tract, RIRS is associated with small remnant stone fragments retained in the kidney. One patient developed Steinstrasse, despite indwelling stent. Previous studies have shown that patients with large stones undergoing RIRS are at a risk of developing Steinstrasse. The percentage of patients developing Steinstrasse among patients with renal stones of diameter 2 to 3 cm has been reported to be 17%,⁵ whereas that among patients with stones of diameter >4 cm has been reported to be 18.7%.³¹ Therefore, the risk of Steinstrasse among patients with large stones is high, which highlights the importance of taking special care to avoid this complication and the impending risk of anuria in patients with a solitary kidney. We recommend that large kidney stones fragments be directly removed by graspers or baskets, or stage treatment, but not fragmented into pieces.

Patients with a solitary kidney are also at a high risk of acute renal injury after endoscopic procedure. Bucuras and colleagues²¹ have shown that for patients with a solitary kidney, the frequency of post-PCNL acute renal injury was significantly greater compared to those with two kidneys. Early animal studies have implicated high-pressure irrigation, ensuing parenchymatic damage and focal scarring of the kidney, as the reason for the acute renal injury following ureteroscopy.³² No significant difference in acute renal injury frequency was observed between RIRS and PCNL in our study. We adopted fiber optic ureteroscope to perform RIRS, which is associated with higher success rate of ureteroscope insertion and UAS insertion. Use of small size ureteroscope and UAS help maintain a continuous irrigant outflow and lower intrarenal pressure, thereby minimizing the chances of renal impairment and risks of infection.

Long-term complications are very important in renal calculi patients with a solitary kidney. Ureteral stricture is a serious complication following RIRS. With the development of ureteroscopes and the use of UAS, incidence of ureteral strictures decreased considerably to as low as 1.4%.³³ Long-term post-PCNL renal function is generally well preserved. Canes and colleagues³⁴ reported modest overall renal function improvement for as much as 1 year of follow-up. Even though our follow-up period was not long, we have not observed any case of ureteral stricture or renal function impairment as a postoperative complication.

This study still has some limitations. First, the sample size was relatively small because of its retrospective nature. In addition, the choice of the treatment modality was made on the basis of the patients' comorbidities, anatomy of the renal collecting system, and patient's preference; this induces selection bias and differences in the background of patients in the two groups. These drawbacks can be overcome by conducting future prospective studies that are more longitudinal and larger in scale, which would allow comparison of long-term effects of RIRS and PCNL for the removal of large stones in patients with a solitary kidney.

Conclusions

The choice of the procedure should be made carefully with consideration of disastrous complications and should count on patient's general condition, as well as physician's experience with the procedures and preference when managing these special patients. Our findings revealed that PCNL is superior in terms of efficiencies and stone-free rate in the treatment of large renal calculi in patients with a solitary kidney. With fewer repeated surgical procedures, higher EQ, acceptable complication rates, and comparable total costs, PCNL is the first choice, except for specific indications such as use of anticoagulant drugs or severely obese patients. For patients with CSD >30 mm, we recommended PCNL as first-line treatment with high efficacy. As for specific indications such as anticoagulant drugs, RIRS is a safer choice with fewer complications and acceptable final stone-free rate.

Footnotes

Acknowledgments

Sources of support: National Natural Science Foundation of China (81370806), and Science and Technology Commission of Shanghai Municipality (13DZ1941205, 11411950102).

Author Disclosure statement

No competing financial interests exist.

Abbreviations Used

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