Is Tubeless Percutaneous Nephrolithotomy Really Less Injurious Than Standard in the Midterm?

Abstract

Purpose:

To compare renal injury and vascular resistance between standard and tubeless percutaneous nephrolithotomy (PCNL) in patients who had undergone procedures for kidney stone by using colored Doppler ultrasonography (CDUS).

Patients and Methods:

All consecutive PCNLs were evaluated between 2009 and 2011. Patients in whom access was in the lower pole, and who regularly visited our outpatient clinic were enrolled in the study. Patients who underwent standard PCNL were included in group 1, and patients who underwent tubeless PCNL were included in group 2. All data were collected from patients' files. CDUS was performed to evaluate the resistive index (RI), parenchymal thickness, and parenchymal echogenicity before the operation, in the early postoperative period (7 days after catheter removal in group 1 and 7 days postoperatively in group 2), and during the midterm period (6 months postoperatively). Statistical significance was accepted at P<0.05.

Results:

The mean patient age was 47.54±13.26 years. There were 33 patients in group 1 and 28 patients in group 2. The mean follow-up duration was 10.71±1.2 months. There were no significant differences in demographic data between the two groups. The hospital stay was longer in group 1 than in group 2 (P=0.038). The mean operative time was shorter in group 2 than in group 1 (P=0.001). An increase in RI and a decrease in parenchymal thickness in the midterm follow-up period were noted when compared with the preoperative RI kidneys that had undergone operations in the lower pole.

Conclusions:

Although tubeless PCNL was successful and was associated with a shorter hospital stay and less kidney damage in the short-term period compared with standard PCNL, both procedures may cause an almost equal degree of damage in the midterm.

Introduction

P ercutaneous nephrolithotomy (PCNL) broke new ground in the surgical treatment of patients with nephrolithiasis.¹ This procedure was recently used in the treatment of patients with nephrolithiasis who could not be treated by extracorporeal shockwave lithotripsy (SWL) and management of nephroliths larger than 2 cm.² PCNL is associated with low morbidity and is minimally invasive compared with open surgery. These characteristics allow for the potential replacement of open surgery by PCNL.

PCNL is currently the standard surgical treatment of patients with nephrolithiasis. This procedure mainly involves accessing the kidney through a small hole, reaching the calculus, and removing it from the kidney. At the end of the procedure, a nephrostomy catheter is placed into the kidney through this hole to tamponade bleeding and allow for a secondary intervention and temporary urinary drainage. Unfortunately, the nephrostomy catheter may create discomfort, increase analgesic requirements, and even prolong hospitalization. As a result of these problems and in the light of improvements in endoscopic surgical techniques, the standard PCNL procedure has been modified. In this context, tubeless PCNL was first used in 1997.³ Later, many studies have evaluated the safety, feasibility, and efficiency of tubeless PCNL.^4,5 Although PCNL is a minimally invasive endoscopic surgical method, the kidney morphology may be affected and renal injury may result.

In light of these data, we used color Doppler ultrasonography (CDUS) to evaluate renal parenchymal damage and vascular resistance in patients who underwent standard and tubeless PCNL. To our knowledge, this is the first such midterm follow-up of renal injury caused by standard and tubeless PCNL using CDUS in the literature.

Patients and Methods

This was a retrospective study. All patients fully understood the treatment and aim of this study, and written informed consent was obtained. Ethical approval for this study was obtained from our institute's ethics committee.

Between July 2009 and April 2011, a total of 223 patients underwent PCNL. The European Association of Urology Guidelines on Urolithiosis was referred to for the operative indications.^5,6 PCNL was performed in patients with nephroliths larger than 2 cm and in whom SWL could not be performed and/or was unsuccessful. Diagnosis by radiography of the kidneys, ureters, and bladder or ultrasonography (US) at the patient's first admission to the outpatient clinic. All patients were evaluated with intravenous urography and noncontrast urinary CT before the operation.

Only 61 of 258 patients with complete data in the files, who regularly visited the outpatient clinic, and who underwent operations involving lower pole access were evaluated. All of the patients were divided into two groups. Group 1 comprised 33 patients who underwent standard PCNL, and group 2 comprised 28 patients who underwent tubeless PCNL.

The following demographic data were recorded from the patients' files preoperatively: Age, sex, kidney stone burden, American Society of Anesthesiologists (ASA) score, body mass index (BMI), urine analysis results, urine culture results, serum creatinine level, and hemoglobin level. The operative time, complications, hemoglobin level, serum creatinine level, and duration of hospital stay were recorded as operative data. The residual stone burden, change in hemoglobin level (delta hemoglobin=preoperative hemoglobin level – postoperative hemoglobin level) were recorded as postoperative data. The operated and contralateral kidneys were evaluated with CDUS preoperatively, in the early postoperative period (1 week after nephrostomy catheter removal in patients who underwent standard PCNL, and during the first postoperative week in patients who underwent tubeless PCNL) and in the midterm (6 months postoperatively). The renal resistive index (RI), parenchymal thickness, and parenchymal echogenicity were recorded.

The complications in our study were classified according to the modified Clavien classification.⁶

Patients were excluded from the study if they underwent open and/or endoscopic renal surgery, had renal failure, had previous pyelonephritis, had renal scarring before surgery, or needed multiple renal access routes.

Surgical procedure

In this series, all PCNL procedures were performed under general anesthesia. The standard PCNL procedure was performed as follows. First, a 6F ureteral catheter (R&D Tech Inc., MA) was inserted into the affected kidney, and a Foley catheter was inserted into the urethra with the patient in the lithotomy position. Next, the patient was placed in the prone position. Access into the kidney was achieved from the lower pole using an 18-gauge percutaneous needle (Plasti-Med, Istanbul, Turkey) with fluoroscopic guidance (Toshiba Medical Systems, Japan). When urine flow through the needle was observed, a sensor guidewire (Plasti-Med, Istanbul, Turkey) was placed into it. A 30-F Amplatz sheath (Plasti-Med, Istanbul, Turkey) was placed into the access pole after dilation of the tract with a balloon catheter (Plasti-Med, Istanbul, Turkey) through the sensor guidewire. Entrance into the kidney was achieved with a 26F nephroscope (Karl Storz GmbH & Co. KG, Tuttlingen, Germany). After reaching the stones, they were broken using a pneumatic lithotriptor (Elmed, Ankara, Turkey) and removed from the kidney with forceps. Under fluoroscopy, the ureteral catheter was retrieved, and the sensor guidewire was passed through it. A 14F nephrostomy tube (Plasti-Med, Istanbul, Turkey) was then inserted over the guidewire.

The tubeless PCNL procedure was performed as follows. A nephrostomy catheter was not inserted into patients with a short operative time, absence of hemorrhage, or perforation of the collecting system. Instead of a nephrostomy catheter, the 6F catheter that had been inserted at the beginning of the PCNL procedure was left in the patient. On the first postoperative day, the ureteral catheter and urethral Foley catheter were removed.

CDUS measurements

Twenty-four hours before CDUS, any nonsteroidal anti-inflammatory drugs that the patients had been using were stopped to avoid influencing the evaluation results.⁷ All patients were fasted for at least 12 hours and were rested for at least 30 minutes before CDUS to ensure objective results. All evaluations were performed by the same radiologist (IB) and with the same ultrasonography device (50-Hz wall filter and 2- to 5-MHz convex transducer) (Nemio 35/SSA-550A; Toshiba, Japan). The thickness of the lower pole, midpolar area, and upper pole; parenchymal echogenicity; and RI of the operated and contralateral kidneys were measured. Parenchymal thickness was measured by the renal sinus fatty tissues and the shortest distance between the capsule.

Echogenicity was evaluated between the two groups by comparing liver echogenicity as follows: Grade 0, renal parenchymal echogenicity lower than liver echogenicity; grade 1, equal renal and liver echogenicity; and grade 2, renal echogenicity higher than liver echogenicity. Doppler spectrums were obtained from the arcuate arteries at the corticomedullary junction. Doppler angles were set between 30 degrees and 60 degrees for all measurements. At least three measurements including the upper, midpolar, and lower poles were performed in both kidneys of all patients. The average of these three measurements was calculated in all evaluations. Pulse repetition frequencies were decreased to the minimal level not posing aliasing, and waveforms were obtained by setting the pulse repetition frequencies at this level. A spectrum was accepted as normal when at least three to five similar waveforms were obtained. The arterial peak systolic and end-diastolic velocities were determined, and the RI values were measured using the software of the US device. The formula for the RI was as follows: RI=(peak systolic velocity–diastolic velocity)/peak systolic velocity.

Statistical analysis

The Statistical Package for the Social Sciences (SPSS) for Windows 16.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. The independent-samples t test was used to compare measurable values, the Kruskal–Wallis test was used for variability analyses, the Wilcoxon signed-ranks test was used for group analysis of nonparametric values, and the Mann–Whitney U test was used for comparisons between the groups. Statistical significance was accepted at P<0.05.

Results

The mean patient age was 47.54±13.26 years, and there were 18 female and 43 male patients in this study. There were 33 patients (13 female, 20 male) in group 1 and 28 patients (5 female, 23 male) in group 2. The mean follow-up duration was 10.71±1.2 months. There were no significant differences between the two groups in age, BMI, stone burden, ASA score, delta hemoglobin, preoperative hemoglobin, or serum creatinine level (Table 1).

Table 1.

Comparison of Patients' Demographic Data

Parameter	Group 1 (n=33)	Group 2 (n=28)	P
Age (years)	48.67±13.29	46.21±13.34	0.476
Stone burden (cm)	4.45±1.26	3.98±1.40	0.170
Preoperative serum creatinine level (mg/dL)	0.99±0.37	0.97±0.32	0.879
ASA score	1.18±0.39	1.18±0.39	0.974
BMI (kg/m²)	24.82±3.70	24.14±2.10	0.395
Preoperative hemoglobin level (mg/dL)	13.31±1.66	13.41±1.99	0.853
Operative time (minutes)	107.88±48.48	69.64±31.00	0.001^*
Delta hemoglobin level (mg/dL)	1.31±1.40	0.67±2.51	0.230
Hospitalization (days)	3.79±1.65	3.04±0.96	0.038^*

ASA=American Society of Anesthesiologists; BMI=body mass index.

Statistically significant P value.

The hospital stay was significantly longer in group 1 than in group 2 (P=0.038), and the operative time was significantly shorter in group 2 than in group 1 (P=0.001) (Table 1). There was no statistically significant difference between the groups in terms of complications, stone-free rates, or urine culture results (P=0.519, P=0.286, and P>0.05, respectively).

CDUS examination revealed no significant differences between the groups in terms of the RI of the lower, midpolar, and upper poles of the operated kidneys; parenchymal thicknesses; or parenchymal echogenicities before the operation (P=0.112, P=0.059, P=0.233, and P=0.357, respectively) (Table 2).

Table 2.

Comparison of Renal Resistive Index and Parenchymal Thickness Between the Two Groups During the Preoperative and Postoperative Early and Midterm Using Color Doppler Ultrasonography

Parameter	Group 1 (n=33)	Group 2 (n=28)	P
Preoperative RI of the lower calix	0.664±0.049	0.644±0.051	0.112
Average preoperative RI of the mid and upper calices	0.663±0.052	0.639±0.043	0.059
Early postoperative RI of the lower calix	0.698±0.049	0.666±0.050	0.013^*
Average early postoperative RI of the mid and upper calices	0.661±0.033	0.648±0.039	0.148
Midterm postoperative RI of the lower calix	0.667±0.042	0.648±0.051	0.448
Average midterm postoperative RI of the mid and upper calices	0.665±0.047	0.643±0.045	0.070
Preoperative parenchymal thickness	11.485±2.221	12.221±2.553	0.233
Postoperative parenchymal thickness	10.924±2.287	11.821±2.595	0.156

RI=resistive index.

Statistically significant P value.

In the early follow-up period, CDUS showed an increase in the RI of the lower poles of the operated kidneys in both groups when compared with the preoperative RI. The increase in the RI was more marked in group 1 than in group 2 (P=0.013) (Table 2). The RI of the midpolar area and lower poles of the operated kidneys was 0.66 in group 1 and 0.65 in group 2 (P=0.148) (Table 2) in the early follow-up period. Moreover, there was a statistically significant increase in the RI in the midterm follow-up period when compared with the preoperative RI in both groups (group 1, P<0.001; group 2, P<0.001).

When the two groups were compared, the RI in the midterm follow-up period was lower than that in the early postoperative period (group 1, P<0.001; group 2, P<0.001).

Furthermore, when the groups were compared in the midterm and preoperative periods, there was an increase in the RI in the lower poles of the operated kidneys in both groups (group 1, P=0.464; group 2, P=0.097). In contrast, the parenchymal thickness in the midterm period was significantly lower than that in the preoperative period (group 1, P<0.001; group 2, P<0.001). In addition, parenchymal echogenicity was lower in the midterm period than in the preoperative period in both groups (group 1, P=0.157; group 2, P>0.05).

Discussion

PCNL was first defined in 1976 by Fernström and Johansson.⁸ In the light of subsequent developments in surgical techniques and equipment, PCNL began to be used more effectively for nephrolithiasis.^9,10 Although the success of PCNL is affected by kidney anatomy; stone burden, localization, and structure; surgical technique; and surgical experience, the success rate is generally high in the literature.⁹ Moreover, modified surgical techniques were developed, such as PCNL with the patient in the supine position and decreased operative times.^11,12

PCNL is suggested to be the first surgical option in the treatment of patients with nephrolithiasis who cannot be treated by SWL and for nephroliths larger than 2 cm.¹³ The differences between tubeless and standard PCNL and the steps involved in tubeless procedures have been debated.¹⁴ Moreover, Amer and associates¹⁵ recently reported that tubeless PCNL was an alternative to standard PCNL in complicated cases.¹⁵ The variously sized nephrostomy tubes that are inserted at the end of a standard PCNL procedure may have adverse effects such as patient discomfort, requirements for additional analgesia, and longer hospital stays.¹⁶ Although PCNL is a minimally invasive procedure, this method may cause several morphologic defects in the operated kidneys.

In our study, we aimed to investigate renal injuries by comparing RI, parenchymal thickness, and renal echogenicities using CDUS in the preoperative and postoperative (early and midterm) periods among patients who underwent standard and tubeless PCNL.

The effects of PCNL, which has been safely performed worldwide, have been reported in various studies in the literature in terms of anterograde nephrostomy, standard US, CT, dynamic and static renal scintigraphy, positron emission tomography, renal angiography, experimental and histopathologic studies, serum creatinine and urinary enzymes levels, glomerular filtration rate investigations, and measurements obtained from CDUS.¹⁷ To the best of our knowledge, a comparison of renal injury by CDUS between patients who underwent tubeless and standard PCNL procedures has not been reported.

Static renal scintigraphy is an effective method for the identification of renal scars. It has several disadvantages, however, such as high cost, invasiveness, the use of ionizing radiation, the requirement for injections, and the inability to differentiate recent or past scars.¹⁸ Therefore, we preferred to use CDUS, which is noninvasive, radiation free, easily accessible and applicable, and inexpensive.¹⁷ In addition, CDUS can be performed more easily than renal scintigraphy for evaluation of renal injuries.¹⁷

There was no significant difference in the preoperative demographic data between the two groups. The amount of intraoperative hemorrhage was calculated with delta hemoglobin (delta hemoglobin=preoperative hemoglobin level – postoperative hemoglobin level). The hospital stay was significantly shorter in group 2 than in group 1. This result parallels that reported by Yew and colleagues.¹⁹ While the mean hospital stay was 1 day in their study, the mean hospital stay was nearly 4 days in group 1 and 3 days in group 2 in the present study, however. The reason for the prolonged hospital stay in group 2 was that we waited for the postoperative macroscopic hematuria to resolve before discharging the patients. In addition, Yew and coworkers¹⁹ used ureteral stents that were curved at one end, but we left the ureteral catheter, which we had inserted before the operation, in the patient until the first postoperative day. All ureteral catheters and urethral Foley catheters of the patients who underwent tubeless PCNL were removed on the first postoperative day.

In addition, the operative time was significantly shorter in group 2 than in group 1. This result is similar to that reported by Yuan and colleagues.²⁰ We performed tubeless PCNL procedures in patients whose stones were not complicated and who had no hemorrhage in the calix neck and/or renal parenchyma, shortening the mean operative time in group 2.

Although nephrostomy tubes were not inserted in patients who had no hemorrhage or complications during short operations, there were no differences in the complication or stone-free rates between groups 1 and 2. There was no difference in the stone burden before surgery, and the stone-free rates were similar in the two groups. These results may have been related to stone complexity and/or patient-related factors and are similar to those in the literature.^20,21 The most common postoperative complication was fever (modified Clavien I), which was seen in five patients in group 1 and four patients in group 2. The postoperative fever regressed after medical treatment. A Double-J stent was used in four patients (two in group 1 and two in group 2) who had flank pain that could not be managed by medical treatment in the early postoperative period (modified Clavien IIIa). Our complication rate among all 61 patients was 26% (n=16) and is similar to that reported in the literature.⁶ In this series, no patient needed a blood transfusion to treat hemorrhage. Moreover, there was no difference in the delta hemoglobin level between the two groups. SWL treatments were needed in two patients (one in group 1 and one in group 2) who had stones larger than 4 mm.

Ramashdeh and associates⁷ reported that either morphologic distortion or several pathophysiologic discriminations might be calculated by various alternative waveforms' RI values in the kidney.⁷ In light of this study, Halevy and coworkers¹⁸ reported that renal defects might be determined by CDUS. The intrarenal RI indicates the degree of vascular resistance depending on pathophysiologic changes in the renal arteries. Our study is the first to use CDUS to compare renal injury between patients who underwent tubeless and standard PCNL procedures. Kilic and colleagues²² evaluated the RI in the preprocedural and postprocedural PCNL periods in patients with ureteropelvic stones and urinary obstruction. They also reported the cutoff RI for renal function; loss was determined at 0.70. No patients in our series, however, had ureteropelvic stones or urinary obstruction, and the average preoperative RI between the two the groups was <0.70.

In our study, there was no difference in the RI of the lower, midpolar, and upper poles in the preoperative and postoperative periods between the two groups. Furthermore, the echogenicities and parenchymal thicknesses of the kidneys did not differ in the preoperative and postoperative periods between the two groups. The rate of increase in the RI of the lower pole was significantly higher in group 1 than in group 2 in the early postoperative period. There was also an increase in the RI in the lower pole in the postoperative period (early and midterm) compared with the preoperative period. In a comparison between the mid and early postoperative periods, a decrease in RI was revealed in both groups. In addition, the midterm RI was higher than the preoperative RI in both groups, but the difference was not statistically significant. There was no difference in the RI between Groups 1 and 2 in the mid-term period.

In light of these data, although renal injury caused by PCNL could be identified in the early postoperative period with CDUS, it may be claimed that PCNL is innocuous to the kidney in the mid postoperative period. In addition, the rate of increase and/or decrease in the RI did not affect patients' clinical course in this series. If more long-term studies of the RI in PCNL are performed, additional successful clinical effects of the RI may be demonstrated.

Kilic and coworkers¹⁷ reported no renal morphologic defects 6 months after standard PCNL based on CDUS findings. They followed up patients for only 6 months, however, and presented their findings as long-term results. The mean follow-up period was 10.7 months in our series, and as we mentioned above, this was the midterm follow-up. In this series, the data of the tubeless and standard PCNL procedures were evaluated retrospectively in a selected population. In light of the CDUS findings, our study is unique in that tubeless PCNL resulted in less damage to the kidney than standard PCNL in the early postoperative period in these selected patients.

There were several limitations to our study. CDUS is a technique in which the outcomes of the examination depend on both the patient and clinician. Although all CDUS examinations were performed by the same radiologist (IB) in our series, there were some difficulties during the follow-up period because of the patients' requirements, such as breath holding and fasting for at least 12 hours. When CDUS could not be performed efficiently, the patients were asked to return to the outpatient clinic 1 day later. Therefore, we attempted to overcome this nonoptimized CDUS procedure. The number of patients in our series was low because patients who underwent PCNL did not regularly come to the outpatient clinic. This may have been related to the fact that patients who underwent PCNL were successfully followed up at peripheral urology outpatient clinics. In addition, the tubeless procedure is not actually tubeless, because of the use of a 6F ureteral catheter. Tubeless PCNL procedures have been described in the literature.^12
–14 We used the tubeless procedure instead of PCNL without a nephrostomy catheter as described elsewhere.^12
–14

Conclusion

PCNL is a minimally invasive procedure recently used for the management of nephroliths larger than 2 cm. When tubeless PCNL is performed in selected patients, it is associated with a short hospitalization period. In addition, tubeless PCNL may be associated with a stone-free rate as high as that in standard PCNL. Moreover, it results in lower renal injury than standard PCNL in the short-term follow-up period in selected patients. In the midterm, neither standard nor tubeless PCNL procedures are injurious to the kidney, based on CDUS findings.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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