Supracostal Upper Pole Endoscopic-Guided Prone Tubeless “Maxi-Percutaneous Nephrolithotomy”: A Contemporary Evaluation of Complications

Abstract

Objective:

To develop a contemporary complication profile for supracostal upper pole endoscopic-guided prone tubeless “maxi-PCNL” to evaluate the need for change.

Materials/Methods:

We identified patients undergoing supracostal upper pole percutaneous nephrolithotomy (PCNL) by a single surgeon at a high volume tertiary care stone center between October 2010 and April 2017. Access was obtained with ureteroscopic guidance. The tract was dilated to 30F through radial balloon dilation. All cases were tubeless with ureteral stent for 5–7 days. Preoperative, operative, and postoperative variables were recorded. We recorded need for blood transfusion, angioembolization, thoracentesis and/or chest tube insertion, intensive care unit (ICU) admission, and 30-day readmission.

Results:

A total of 375 patients were included. Mean age was 57 years and 59% were women. Mean body mass index was 33 kg/m². Mean stone burden was 35 mm. The mean operative time was 99 minutes. Median stay was 1 day. There were no complications because of prone position. Postoperative complications included pleural drain (4%), transfusion (6.7%), and angioembolization (0.5%). Transfusion rates were higher in patients with preoperative hemoglobin <10 mg/dL (28% vs 5.1%, p < 0.00001). Rate of ICU admission and readmission was 4.5% and 7.5%, respectively. Transfusion (p ≤ 0.001), pleural drain (p = 0.0002), and readmission (p = 0.030) were associated with ICU admission. Male gender was associated with readmission (10.3% vs 5.5%, odds ratio = 3.1, p = 0.012).

Conclusions:

In supracostal upper pole endoscopic-guided prone tubeless Maxi-PCNL, pulmonary complication rate was lower than previously reported and bleeding complications were comparable with mini-PCNL series. Establishing contemporary complication rates will help to assess the need for evolution to mini-PCNL or lower pole supine PCNL.

Introduction

Percutaneous nephrolithotomy (PCNL) is the preferred treatment modality for kidney stones >2 cm, complex formations such as staghorn calculus, and certain renal anomalies such as caliceal diverticulum or horseshoe kidney. Both success and safety of PCNL have been well established in the literature. Stone-free rates approach 95% in some series, whereas the majority of postoperative complications are Clavien grades 1–2. Major postoperative complications such as pneumothorax (0.3%), sepsis (0.3%), arteriovenous fistula (0.2%), need for transfusion (5.7%), or death (0.1%) are rare.^1,2

Minimally invasive PCNL (MPCNL) is a modification of traditional PCNL using smaller caliber percutaneous access tract and instruments. Employing MPCNL purportedly decreases risk of complications associated with a traditional caliber percutaneous access.³ Similarly, supine PCNL (SPCNL) theoretically offers safer anesthesia, obviates the need for repositioning thus decreasing operative time, and allows antegrade and retrograde approach to be performed simultaneously.⁴

At our institution, we preferentially perform a supracostal access to the upper pole to perform endoscopic-guided prone PCNL with a 30F sheath. Our objective was to define our current complication rate and compare our results with the existing literature, specifically with regard to MPCNL and SPCNL, to investigate a need for offering these alternative approaches.

Materials and Methods

We identified patients who underwent PCNL by a single surgeon at a high volume tertiary referral stone center between October 2010 and April 2017 by querying an IRB-approved prospectively collected kidney stone registry. We collected patient demographics, intraoperative characteristics, and postoperative complications by a combination of registry query, retrospective chart review of clinical notes, radiology reports and images, and operative notes in the electronic medical record. Patients who underwent percutaneous renal access by interventional radiology were excluded. These were patients who either had a urinary diversion that precluded retrograde access, a transplant kidney, or required emergent decompression for a septic presentation. Patients who had infracostal, interpolar, or lower-pole access were excluded.

Baseline patient demographics collected were age, gender, and body mass index (BMI). Cumulative stone burden on the side of operation was calculated by measuring the longest dimension of the stone(s) in any plane on preoperative CT or kidney, ureter, and bladder radiograph (KUB; if more than one stone was present, measurements of longest dimension of all stones were added together). Preoperative urine culture was recorded as being positive or negative.

After induction of anesthesia and intubation, the patient is placed prone on a split-leg bed. Percutaneous access into the collecting system is guided by endoscopy and fluoroscopy as previously described—a flexible ureteroscope is navigated into an appropriate posterior upper pole calyx and bullseye technique is used to puncture onto the tip of the scope into the collecting system.⁵ The angle of puncture to the upper calyx is initially assessed in the vertical (0°) position. The tip of the ureteroscope is oriented to look head on into the calyx. If on fluoroscopic image the tip of the ureteroscope is curved, then the image intensifier is rotated until the tip of the scope is straight for an “in-line access.” Typically, this requires a <10° adjustment of the needle angle. The tract is dilated using a standard 30F radial balloon dilator. Stones are removed through a combination of basket extraction and ultrasonic lithotripsy. All patients were treated tubeless irrespective of bleeding or extravasation, with a retrograde ureteral stent for 5–7 days postoperatively. Patients with significant residual stone burden underwent second-look ureteroscopy 2 weeks postoperative. Intraoperative variables recorded included laterality and duration of procedure.

Postoperative variables recorded included need for blood transfusion, angioembolization, thoracentesis and/or chest tube insertion, intensive care unit (ICU) admission, and 30-day readmission. Length of admission was also recorded. Patients with a postoperative hemoglobin <7 mg/dL, postoperative hemoglobin <8 mg/dL with a cardiac history, or anemia in the presence of hemodynamic instability underwent transfusion. For those who received transfusion, volume of blood products transfused was recorded and serum hemoglobin was recorded on preoperative blood work-up, day of transfusion, and on discharge. Transfusion rates were stratified based on whether preoperative hemoglobin was above or below 10 mg/dL. All ICU admission and readmission rates were recorded and were not restricted strictly to complications relating to PCNL.

We sought to find independent associations between patient characteristics and postoperative complications—a multivariable model was created using age, BMI, gender, year of surgery, stone burden, operative time, and urine culture as input variables. A logistic regression using the multivariable model was performed to test for associations between variables and complications while controlling for the other variables. The cutoff value for statistical significance was p < 0.05. Statistical calculations were performed using SAS 9.4 (SAS Institute, Inc., Cary, NC).

Results

Six hundred and six PCNL procedures were performed during the study period. After excluding 139 patients who had percutaneous access by interventional radiology, 46 patients with interpolar and 46 patients with lower-pole access, 375 patients were included in the analysis (Table 1). A total of 327 individual patients underwent 375 PCNLs. Mean age was 56.7 ± 14.3 years old. Fifty-nine percent were women. Mean BMI of the sample was 33.2 ± 9.3 kg/m² (Table 1).

Table 1.

Patient Demographics

Patient demographics	n
No. of PCNL	606
Access obtained by interventional radiology	139
Interpolar access	46
Lower pole access	46
Mean age ± SD	56.7 ± 14.3
Mean BMI ± SD	33.2 ± 9.3

BMI = body mass index; PCNL = percutaneous nephrolithotomy; SD = standard deviation.

One hundred and sixty-two (43.2%) procedures were right sided and 213 (45%) were left sided. Mean stone burden was 35.2 ± 20.6 mm. Approximately one-quarter of patients (91; 24.7%) had a positive urine culture within 30 days of PCNL. The mean operative time was 99.2 ± 46.2 minutes. Median length of stay was 1.2 days (Table 2).

Table 2.

Intraoperative Variables

Intraoperative variable	n (%)
Right-sided PCNL %	162 (43.2)
Left-sided PCNL %	213 (45.0)
Mean stone burden in mm ± SD	35.2 ± 20.6
Positive urine culture within 30 days preoperatively	91 (24.7)
Mean operative time in minutes ± SD	99.2 ± 46.2
Median length of stay in days	1.2

A supracostal 12th-rib puncture was performed in 88% of patients, whereas a supracostal 11th-rib puncture was performed in 12% of patients. No punctures were performed above the 10th rib.

Fifteen (4%) of the procedures required postoperative thoracentesis or chest tube insertion (Table 3).

Table 3.

Complication Rates

Complication type	n (%)
Blood transfusion (preoperative hemoglobin <10 mg/dL)	7 (28.0)
Blood transfusion (preoperative hemoglobin ≥10 mg/dL)	18 (5.1)
Selective angioembolization	2 (0.5)
Thoracentesis and/or chest tube insertion	15 (4.0)
ICU admission	17 (4.5)
Readmission within 30 days of PCNL	28 (7.5)

ICU = intensive care unit.

There were 25 (6.7%) transfusions. Patients were stratified into two groups: those with preoperative hemoglobin <10 mg/dL (25) and ≥10 mg/dL (350). There was a significantly (p < 0.0001) higher transfusion rate in the low hemoglobin group (7/25; 28%, see Table 3) compared with the normal hemoglobin group (18/350; 5.1%, see Table 3).

Two patients (0.5%) underwent selective angioembolization for persistent bleeding (Table 3).

Seventeen (4.5%) and 28 (7.5%) of patients required ICU admission and had readmission within 30 days, respectively (Table 3). Four patients were readmitted for reasons unrelated to the PCNL procedure. Seven patients were admitted with concern for urinary infection, five for pulmonary complication, two for severe bleeding, and three for mild to moderate gross hematuria after stent removal. There were two readmissions for flank hematoma and one for pulmonary embolus.

Need for transfusion (p ≤ 0.001), pleural drain (p = 0.0002), and readmission (p = 0.030) were associated with the need for ICU admission.

On multivariate analysis, male gender was significantly associated with greater risk of readmission (10.3% vs 5.5%, odds ratio [OR] = 3.1, p = 0.012). No other independent associations were found between the variables in the model and the outcome complications.

Discussion

We sought to characterize the complication profile for patients undergoing supracostal upper pole renal access and PCNL by a high volume surgeon at a tertiary care stone referral center. Surgical technique was consistent throughout the study period—upper pole access was gained, traditional caliber (30F) “maxi-PCNL” was performed, and patients were left “tubeless” with internal Double-J stent.

Our patient cohort was older and more obese than contemporary comparative series. The mean age (57 years) of our patients was higher than that of the Clinical Research Office of the Endourology Society (CROES) cohort (49.2 years).² BMI too was higher in our group (33.2 ± 9.3 kg/m²) than both CROES and Nationwide Inpatient Sample (NIS; 26.8 ± 5.9 kg/m², 30.4 ± 7.2 kg/m², respectively).^2,6 This is reflective of the local state population, where 31.5% of the population is obese (BMI >30).⁷ Although previous studies have shown that increased BMI is an independent risk factor for pulmonary complication after PCNL, we did not see any association of BMI with complications on multivariable analysis.⁸

The literature is conflicting on the associations between male gender and risk of post-PCNL complications. Wei and colleagues showed an association between male gender and risk of postoperative complications, whereas Rivera and Viers did not find any such associations.^9,10 Our cohort showed a strong increase in odds of readmission for men when controlling for other variables (OR = 3.1, p = 0.012). The reason for this difference in readmission rate is unclear. Previous literature does not show any gender-related difference in morbidity related to indwelling stents.¹¹ We hypothesize that higher voiding pressures in men may increase the risk of stent reflux and delayed bleeding from tubeless PCNL.

Overall reported complication rate is widely varied in the literature. Seitz and coworkers conducted a meta-analysis of PCNL series and found an overall rate of 4.7% for Clavien ≥3 complications.¹² An analysis of the NIS database by Tyson and Humphreys calculated that 14.4% of patients undergoing PCNL have at least one complication.¹³ The total complication rate in this study was 15.7%. The total rate of complications classified as grade III or higher using the Clavien–Dindo classification of surgical complications was 9%.¹⁴

Previous literature has suggested that access into the upper pole is more often associated with complications, especially intrathoracic complications. Lojanapiwat and Prasopsuk, Munver and colleagues, and Patel and colleagues all examined large series of patients undergoing upper pole access similar to our own series.^15
–17 They demonstrated pulmonary complication rate requiring intervention of 2.2%, 2.3%, and 5.6%, respectively. The risk was higher in these series with supracostal approaches (Lojanapiwat and and Prasopsuk and Munver and colleagues reported 5.3% and 7.1%, respectively)—our rate of intervention for pulmonary complication compares favorably with these series.^15,16 In contrast, a series of supracostal upper pole access demonstrated a 4% risk of patients undergoing pleural drainage.¹⁸

Variations in surgical technique, advances in endoscopic surgical technology, discordant patient populations, increasingly strict transfusion criteria, and individual surgeon preference make it difficult to compare transfusion rate across studies. Historically, 1–12% of patients have required transfusion.¹² Modern series generally report transfusion rates of <5%.^16,19,20 Our transfusion rate was 6.7%, which is similar to that of the worldwide CROES cohort (5.7%) and the NIS (4.9%).^2,6 For those patients who had preoperative hemoglobin >10 mg/dL, this rate decreased to 5.1%. We believe that this rate compares favorably given that no selection criteria was applied to omit nephrostomy tube, reflecting a true transfusion rate for a large “tubeless” series. This suggests that leaving an internal Double-J stent as the sole means of renal drainage is safe postoperatively. In a meta-analysis of randomized clinical trials comparing various tubeless and standard techniques, Lee and coworkers showed that although there was a significant change in hemoglobin levels, there was no change in transfusion rates when comparing standard PCNL with “tubeless with stent.”²¹ The risk of transfusion for patients with a preoperative hemoglobin of <10 mg/dL was very high at 28%. This is important to note from a surgical planning and patient-counseling standpoint.

Two patients underwent selective angioembolization for postoperative bleeding (0.5%). This is in line with the rate of 0.4% reported in the Seitz and coworkers meta-analysis.¹²

Twenty-eight patients (7.5%) were readmitted within 30 days (four for reasons unrelated to PCNL). Although Moses and colleagues used 90-day readmission as an endpoint, their readmission rate was slightly higher at 8%.²² Three patients were readmitted for gross hematuria subsequent to stent removal, although only one of these was immediately following the clinic procedure.

Seventeen (4.5%) were admitted to the ICU during their postoperative hospital course. Increased risk of transfusion, pleural complication, and readmission were associated with admission to the ICU. It stands to reason that patients requiring unexpected interventions, including transfusion and pleural drain, would be more likely to be admitted to the ICU, and subsequently, be more at risk of needing readmission.

MPCNL uses a smaller caliber working sheath and instrument than traditional PCNL.³ As a consequence, it is thought to be less “invasive” and thus have a lower risk of complications. An animal study by Traxer and colleagues did not show any difference in renal parenchymal damage or size of fibrotic scar between the two techniques.²³ A randomized controlled trial by Cheng and associates showed a higher transfusion rate in the traditional PCNL group vs the MPCNL group (10.4% vs 1.4%).²⁴ A similar but smaller trial by Zhong and colleagues showed a statistically nonsignificant difference between the two groups (3.4% vs 12%).²⁵ Our cohort demonstrates a much lower transfusion rate for traditional PCNL. Both of these studies, as well as a retrospective analysis by Giusti and associates, show a significantly shorter operative time for the traditional technique.²⁶ Further, the Giusti study shows MPCNL to have lower stone-free rate and similar length of stay than the traditional technique.²⁶

Supine position for PCNL is purportedly safer and easier on the patient from an anesthesia standpoint, requires no repositioning of the patient after start of procedure, and offers the capability of performing ureteroscopy and nephrolithotomy at the same time.⁴ In our experience, adequate pulmonary ventilation in the prone position has not been prohibitive—we routinely operate on patients with a BMI >40 with and without cardiopulmonary comorbidities. In this series, we did not experience any complications related to prone positioning, and no cases had to be aborted because of poor ventilation. By using a split-leg bed, the patient is placed prone at the very beginning of the case, and retrograde ureteroscopy is a crucial aspect of our access technique and also allows for simultaneous antegrade and retrograde approach.

A meta-analysis by Liu and coworkers and a randomized controlled trial by Zhan and associates comparing prone PCNL vs SPCNL both demonstrated that although operative time was shorter for supine patients, there was no difference in the overall complication rate or in the stone-free rate.^4,27 The pooled transfusion rates were 4.3% compared with 8.8%, although this did not reach statistical significance, contrary to the findings of the included studies by Shoma and Elshal and Falahatkar and coworkers, which did show a 2.5–3 times increase in odds of transfusion.^28,29 A recent meta-analysis, including the CROES database, suggested lower stone-free rates (70% vs 77%) and longer operative times (90 vs 83 minutes) with the supine approach compared with prone.³⁰ It also reported that randomized controlled studies demonstrated no differences in transfusions, complications, or length of stay with SPCNL compared with prone.³¹

Conclusions

The safety profile of PCNL with endoscopic-guided supracostal upper pole access tubeless “Maxi-PCNL” is associated with rates of major complication, pulmonary complication requiring drainage, transfusion, embolization, and readmission that are in line with modern PCNL series, including those assessing MPCNL and SPCNL. Moreover, our study yields lower rates of complications compared with historical series for supracostal puncture. Knowing the contemporary risks of supracostal maxi-PCNL will help us as we assess the potential value of evolution to MPCNL or lower pole SPCNL.

Surgical technique requires continued reassessment and refinement. The goal of this study was to redefine the contemporary complication rates of supracostal upper pole PCNL with 30F tracts. Only once we know where we are, can we set our sights on where we need to be. Our next step will be to prospectively assess the impact of changes in technique to see if we can impact our bleeding and pulmonary complication rates.

Footnotes

Acknowledgment

This study underwent review and approval by the IRB of the Cleveland Clinic Foundation.

Author Disclosure Statement

No competing financial interests exist.

Abbreviations used

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