Increasing Body Mass Index Steepens the Learning Curve for Ultrasound-guided Percutaneous Nephrolithotomy

Evaluating the learning curve of total ultrasound guided percutaneous nephrolithotomy in complex renal stones using"30-degree triangulation"technique

PURPOSE

To investigate the learning curve of in the training of total ultrasound(US) guided percutaneous nephrolithotomy(PCNL) in complex renal stones using "30-degree principle" technique.

PATIENTS AND METHODS

A total of 80 patients were included in this study to evaluate the learning curve of US guided PCNL in an inexperienced novice. They were divided into 8 groups based on timing of the surgery to evaluate the outcomes within the groups. The operator has mastered the"30-degree triangulation" technique for US-guided percutaneous renal puncture by education and theoretical study. Two important parameters were reviewed, namely US screening time and puncture time. Other peri-operative data were also recorded.

RESULTS

The mean US screening time was 509.3 s for the first 10 cases. It decreased significantly to an average of 226.3 s through 30 to 40. Although the US screening time gradually shortened with accumulated experience and stabilized at an average of 152.5 s through 70-80 cases, there was no significant difference between the following groups. Puncture time declined from 558.8 s in the first group to a mean of 202.3 s in the patients 30 to 40. Consistent with the trend in US screening time, although puncture time continued to decrease, there was no significant difference between them in subsequent patient groups. There were no significant differences in the hemoglobin drop, stone-free rate(SFR), post-hospitalization, or severe complication rate between each groups.

CONCLUSIONS

The acceptable outcome of PCNL guided by total ultrasound in complex stones could be achieved after 40 cases under the premise of mastering the "30-degree triangulation"technique. The US screening time and puncture time dropped to a relative steady level after 40 times of practice.

Trends in Patient Complexity, Practice Setting, and Surgeon Reimbursement for Urolithiasis: Do Rural Urologists Pay the Price?

OBJECTIVE

To evaluate the relationship between patient complexity, practice setting, and surgeon reimbursement for ureteroscopy and percutaneous nephrolithotomy (PCNL).

METHODS

The "2021 Medicare Physician and Other Provider" file was used to collect Rural-Urban Commuting Area (RUCA) codes and hierarchical condition category (HCC) scores of urologists. Higher HCC score corresponds to higher medical complexity and higher RUCA code corresponds to a more rural area. Medicare reimbursement for ureteroscopy and PCNL were collected. Linear regressions were performed to predict change in reimbursement based on RUCA and HCC scores.

RESULTS

In 2021, 52,816 procedures under Current Procedural Terminology (CPT) code 52356 (ureteroscopy) and 1649 procedures under 50080 or 50081 (PCNL) were billed to Medicare. Mean reimbursement was $338.24 for ureteroscopy and $957.89 for PCNL. For ureteroscopy, higher HCC score predicted lower reimbursement (P <.001). Higher HCC score predicted higher reimbursement for PCNL (P <.01). Average RUCA for ureteroscopy was higher than for PCNL (P = .02). Rural location predicted lower reimbursement for ureteroscopy (P <.001), however, there was no association for PCNL.

CONCLUSION

For ureteroscopy, higher-risk patients are associated with lower reimbursement while the opposite holds true for PCNL. Rural practices were associated with lower reimbursement for ureteroscopy, but there was no association between location and PCNL reimbursement. Together, these findings suggest practice pattern variation between ureteroscopy and PCNL and highlight gaps in reimbursement policy. Risk-adjusted reimbursement should be considered to incentivize urologists to treat complex patients within their practice scope.

Ultrasound-guided percutaneous nephrolithotomy (PCNL) success rates in patients with elevated body mass index: a comparative study

Percutaneous nephrolithotomy (PCNL) is considered gold standard treatment of renal stones larger than 20 mm. Several studies have shown that ultrasound guidance during this procedure is more effective and safer than fluoroscopy. A higher body mass index (BMI) can make ultrasound-guided renal access more difficult and unsuccessful. We present a prospective analysis and comparison of ultrasound-guided PCNL in patients with normal and increased body mass index. We performed a prospective comparison of patients who underwent ultrasound-guided PCNL to remove renal stones by a single surgeon between 2020 and 2022. Patients with BMIs greater than 30 (mean 33.87-obese) were compared to those with BMIs less than 30 (mean 25.69-non-obese). Demographic, perioperative, and follow-up data were collected, analyzed, and included in this study. Total of 98 consecutive patients, with 49 patients in each group were analyzed. No statistically significant differences were observed in terms of stone volume (P = 0.085), stone density (P = 0.5590), location of renal access (P = 0.108), surgery duration (P = 0.38), blood loss (P = 0.54), or laboratory changes after surgery (P = 0.60). 87.76% of obese patients were stone free per CT scan at follow-up, compared to 73.47% of normal-weight patients (P = 0.1238). According to Clavien-Dindo classification, six patients in the non-obese group experienced grade II (10%) and grade III (2%) complications, as opposed to six patients in the obese group with grade I (2%), grade II (6%), and grade III (2%) complications. There was no significant correlation between body mass index and the success or safety of ultrasound-guided PCNL. Although more challenging, a higher BMI should not be an impediment to performing this approach. This method is safe, with no increased incidence of postoperative complications or compromise in stone-free status postoperatively and can diminish or avoid both patient's and medical team's exposure to ionizing radiation.

Ultrasound-Guided PCNL - Why Are We Still Performing Exclusively Fluoroscopic Access?

PURPOSE OF REVIEW

While urologists are traditionally taught to perform percutaneous nephrolithotomy (PCNL) utilizing exclusively fluoroscopy, ultrasound has emerged as a safe alternative. This article showcases the major reasons why ultrasound-guided access should be considered the first-line approach for performing access for PCNL.

RECENT FINDINGS

There continues to be a need to further reduce radiation exposure in the management of kidney stone patients. This review showcases how performing ultrasound-guided PCNL has been associated with a shorter learning curve, increased patient safety, and the ability to perform x-ray free PCNL. Ultrasound-guided PCNL is not only an achievable skill for urologists to learn but provides multiple advantages over traditional fluoroscopic access. As every effort should be given to help reduce radiation exposure for kidney stone patients as well as performing surgeons and operating theater personnel, endourologists should strive to add this technique to their armamentarium.

Low-dose fluoroscopy technique drastically decreases patient radiation exposure during percutaneous nephrolithotomy

Fluoroscopy is essential in percutaneous nephrolithotomy (PCNL) but exposes patients and operating room staff to radiation. We investigated whether a low-dose (LD) protocol could reduce radiation exposure during fluoroscopy-guided access without compromising clinical outcomes. Patients undergoing PCNL with fluoroscopy-guided access at a tertiary care stone center between January 2019 and July 2021 were identified. Prior to September 3, 2020, the Philips Veradius C-arm's default settings were used: standard per-frame dose, 15 pulses per second (PPS) frame rate. After this date, a low-dose protocol was used: reduced per-frame dose, reduced frame rate of 8 PPS for needle puncture and 4 PPS for all other steps. Clinical and radiographical data were retrospectively collected. The primary outcome was cumulative radiation dose. Secondary outcomes were stone-free status (SFS; defined as no fragments ≥ 2 mm) and complications. Multivariate regression analysis was performed. 100 patients were identified; 31 were in the LD group. The LD cohort was exposed to a significantly lower mean cumulative radiation dose of 11.68 mGy compared to 48.88 mGy (p < 0.0001). There were no differences in operative time, fluoroscopy time, stone burden, SFS, or complications. In a multivariable regression model adjusting for several variables, LD protocol was associated with lower radiation dose while skin-to-calyx-distance (STCD) was positively associated with cumulative radiation dose. Low-dose fluoroscopy and decreased frame rate during PCNL decreased radiation exposure fourfold without affecting SFS or complication rates.

Ultrasound-guided renal access and balloon dilation for PCNL in the prone position: results of a multicenter prospective observational study

PURPOSE

To investigate the safety and efficacy of ultrasound-guided renal access and tract dilation using balloon dilators, as well as to identify suitable patients for this technique.

METHODS

Consecutive patients undergoing ultrasound-guided PCNL using balloon dilators between December 2019 and June 2020 in seven large medical centers from China were prospectively enrolled. Demographic and perioperative parameters of the patients were collected. Logistic regression analysis was used to analyze factors that would affect the success rate of tract establishment using ultrasound-guided renal access and balloon dilation.

RESULTS

A total of 170 patients were included in this study, among whom, 91.18% of the (155/170) patients had a successful tract establishment under ultrasound guidance on the first attempt. The stone-free rate was 83.5% and postoperative complications occurred in 14 patients (8.23%). In univariate analysis, history of ipsilateral surgery (p = 0.026), and stone diameter (p = 0.01) were significantly associated with tract establishment failure, while a larger width of the target calyx (p = 0.016) and the presence of hydronephrosis (p = 0.001) were significantly associated with a successful tract establishment. In multivariate analysis, only hydronephrosis in target calyx (p = 0.027) was a favorable factor for successful tract establishment, and the history of ipsilateral renal surgery (p = 0.012) was the only independent risk factor for failure of tract establishment.

CONCLUSION

It was safe and effective to establish percutaneous renal access with balloon dilation under whole-process ultrasound monitoring during PCNL. Furthermore, patients with a hydronephrotic target calyx and without history of ipsilateral renal surgery were most suited to this technique. Trial registration CHiCTR1800014448.

Electromagnetic-guided puncture: a tool or a tale?

PURPOSE OF REVIEW

The puncture technique and site of the puncture can impact the clinical outcome and the development of postoperative adverse events following percutaneous nephrolithotomy (PCNL). The aim of the current review was to discuss the available puncture guidance approaches and outline the potential role of the recently introduced electromagnetic-guided method.

RECENT FINDINGS

The puncture and PCNL tract establishment is usually performed using fluoroscopic or ultrasound guidance or a combination of two approaches. Electromagnetic-guided puncture is one of the most recent advancements of technology. The puncture navigation to the renal collecting system is available after placing a special wire with an electromagnetic tracking sensor into the desired calyx through the flexible ureterorenoscope. The available experimental and clinical studies have shown a high first puncture rate, decreased median time for obtaining a puncture, and shorter learning curves for beginners.

SUMMARY

Fluoroscopic and ultrasound guidance are the main approaches used by urologists. However, these modalities require a steep learning curve, approximately 60 cases for reaching competency. The initial data on electromagnetic navigation have shown the feasibility and potential promising outcomes of this novel approach. New studies are required to investigate its potential implementation opportunities in the daily practice of urologists.

Percutaneous nephrolithotomy - the puncture

OBJECTIVE

To determine what importance is given to the puncture and assistive technologies in percutaneous nephrolithotomy (PNL) in the current urological literature.

METHODS

PubMed was searched for English publications and reviews for the keywords: 'percutaneous nephrolithotomy', 'percutaneous nephrostomy', 'puncture'. The search was limited to the last 5 years, January 2016 until February 2021. Based on 183 abstracts, 121 publications were selected, read, and reviewed. References, older or seminal papers were read and cited if they contributed to a better understanding. A total of 198 references form the basis of this narrative review.

RESULTS

The puncture is frequently referred to as the most crucial part of PNL. In contrast, the influence of the puncture on the failure rate of PNL and the specific puncture-related complications seems to be low in the single-digit percentage range. However, there are no universally accepted definitions and standards measuring the quality of puncture. Consequently, the impact of the puncture on general PNL complications, on stone scores predicting success rates and on learning curves evaluating surgeons' performance have not been systematically studied. Assistive technologies rely on fluoroscopy and ultrasonography, the latter of which is becoming the preferred imaging modality for monitoring the entire procedure. Needle bending, a problem relevant to all puncture techniques, is not addressed in the urological literature.

CONCLUSIONS

The importance attached to puncture in PNL in the current urological literature is subjectively high but objectively low. Some basics of puncture are not well understood in urology. Disciplines other than urology are more actively involved in the development of puncture techniques.

Percutaneous nephrolithotomy with ultrasound-assisted puncture: does the technique reduce dependence on fluoroscopic ionizing radiation?

PURPOSE

The ultrasound-guided (US) puncture in percutaneous nephrolithotomy (PCNL) has demonstrated advantages over traditional fluoroscopy access. The aim of this study was to demonstrate the reduction of fluoroscopy time using this technique during PCNL as the surgeon gained experience.

METHODS

Transversal study performed on 30 consecutive patients undergoing PCNL from March to November 2019. All punctures were performed with US guidance. The patients were divided into 2 groups of 15 each according to the chronological order of the intervention. Demographic data, preoperative parameters, puncture time, fluoroscopy time, stone-free rate and complications were analyzed.

RESULTS

The time of fluoroscopy was considerably reduced as the experience in the number of cases increased, reducing from 83.09 ± 47.8 s in group 1 to 22.8 ± 10.3 s in group 2 (p < 0.01), the time required to perform the puncture was reduced of 108.1 ± 68.9 s in group 1, to 92.6 ± 94.7 s in group 2 (p < 0.67). Stone free rate of 83.3% was obtained globally.

CONCLUSION

US percutaneous renal access is safe and reproducible technique; the main advantage is to reduce exposure to radiation without compromising clinical results and has a short learning curve for urologists with prior experience in PCNL.

Influence of Body Mass Index on the Surgical Outcomes of Flexible Ureteroscopy for Pediatric Upper Urinary Tract Aalculi-A Single Surgeon Experience

OBJECTIVE

To examine the association between body mass index (BMI) and surgical outcomes of flexible ureteroscopy (FURS) for pediatric upper urinary tract calculi and to estimate the influence of BMI percentile on the learning curve of pediatric FURS.

MATERIALS AND METHODS

We reviewed our prospectively maintained database containing children who had kidney or ureteral stones from June 2014 to April 2019. We calculated BMI and plotted it on the Centers for Disease Control and Prevention growth chart for sex and age to estimate BMI percentile. Patient demographics, intraoperative data, stone characteristics, stone-free rate (SFR), and complication rate (CR) were analyzed. Learning curves stratified by BMI percentile groups were generated.

RESULTS

The final analysis included 161 children, of whom 63 (39.1%) had upper body weight percentile (UBW), 64 (39.8%) had normal body weight percentile (NBW), and 34 (21.1%) had lower body weight percentile (LBW). The median stone burden of the 3 groups were 1.14 (IQR 0.50-3.41), 1.13 (IQR 0.70-3.14), and 0.95 (IQR 0.50-1.77), respectively (P = .17). The SFRs were 90.5% (57/63) in the UBW group, 81.2% (52/64) in the NBW group and 70.6% (24/34) in the LBW group (P = .04). The CRs were 15.9% (10/63), 21.9% (14/64), and 29.4% (10/34), respectively (P = .29). The learning curves showed that the SFR of FURS could be improved after about 100 cases. And decreasing BMI could steepen the learning curve of SFR.

CONCLUSIONS

BMI is associated with the SFR of FURS. LBW children had the lowest SFR compared to UBW and NBW children. Lower BMI percentile makes the success of FURS more challenging.