Techniques for fluoroscopy-guided percutaneous renal access: An analytical review

Outcomes of a Single Transverse Chest Roll for Prone Positioning Technique During Percutaneous Nephrolithotomy

OBJECTIVE

To compare anesthetic parameters using a novel prone single transverse chest roll technique (STR) to the standard thoraco-pelvic dual transverse roll technique (DTR).

METHODS

A retrospective review of 441 patients who underwent PCNL between 2018 and 2022 was performed. A total of 4 surgeons were included-surgeon 1 utilized the STR technique while surgeons 2, 3, and 4 used the DTR technique. Anesthetic parameters including end-tidal CO2 (ETCO2), mean arterial pressure (MAP), peak airway pressure (Ppeak), plateau airway pressure (Pplat), positive end-expiratory pressure (PEEP), oxygen saturation (SpO2), and tidal volume (TV) were compared between both groups at 0 (supine), 15-, 30-, and 60-minute post-intubation intervals. Mixed effects regression models with interaction and pairwise comparisons were made between both groups (P <.05).

RESULTS

A total of 581 PCNLs were performed with 199 using STR and 382 using DTR. Surgery duration, ASA class, and age were similar amongst the STR and DTR groups. Estimated blood loss (59cc vs 83cc, P = .007) and length of stay (77 hrs vs 163 hrs, P = <.001) was significantly lower in the STR group. There was a significantly lower Ppeak, Pplat and TV in the STR compared to DTR group at 0, 15, 30, and 60 minutes (P <.001).

CONCLUSION

Usage of a single transverse chest roll during prone PCNL appears to be a safe positioning method. STR patients had lower Ppeak and Pplat at all time points, which has been shown to be predictive of lower blood loss.

Preliminary experience with lost mini percutaneous nephrostomy channel retrieval by methylene blue injection

Percutaneous nephrolithotomy (PCNL) is the primary choice for managing large renal stones and the establishment of mini-/micro-channels has been increasingly gaining practice. The smaller the channel, the easier it is to be lost, which may require a new puncture site and increase the risk of bleeding complications. In this study, we retrospectively reviewed 1,056 PCNL procedures in our single institute, The University of Hong Kong - Shenzhen Hospital, between March 2014 and August 2023. Twenty-three cases of nephrostomy channel loss during mini PCNL were identified, resulting in an incidence rate of 2.2%. Methylene blue was immediately injected into the ureteral catheter to facilitate location and retrieval of the channel. Once extravasation of the dye was identified under rigid ureteroscope, a first guidewire was introduced into the channel for maintenance, followed by another guidewire inserted in parallel to facilitate dilatation. The major reasons for PCNL channel loss were mild hydronephrosis and complete obstruction of the target calyx due to renal stones. Technical success, defined as the ability to retrieve the lost channel within 5 minutes, was 78.3% (n=18/23). Three channels were completely lost and 2 patients showed channel bleeding despite successful identification, all of which required establishment of a new PCNL channel. No major intraoperative nor postoperative complication was observed.

Reducing hand radiation during renal access for percutaneous nephrolithotomy: a comparison of radiation reduction techniques

Percutaneous nephrolithotomy confers the highest radiation to the urologist's hands compared to other urologic procedures. This study compares radiation exposure to the surgeon's hand and patient's body when utilizing three different techniques for needle insertion during renal access. Simulated percutaneous renal access was performed using a cadaveric patient and separate cadaveric forearm representing the surgeon's hand. Three different needle-holding techniques were compared: conventional glove (control), a radiation-attenuating glove, and a novel needle holder. Five 300-s fluoroscopy trials were performed per treatment arm. The primary outcome was radiation dose (mSv) to the surgeon's hand. The secondary outcome was radiation dose to the patient. One-way ANOVA and Tukey's B post-hoc tests were performed with p < 0.05 considered significant. Compared to the control (3.92 mSv), both the radiation-attenuating glove (2.48 mSv) and the needle holder (1.37 mSv) reduced hand radiation exposure (p < 0.001). The needle holder reduced hand radiation compared to the radiation-attenuating glove (p < 0.001). The radiation-attenuating glove resulted in greater radiation produced by the C-arm compared to the needle holder (83.49 vs 69.22 mGy; p = 0.019). Patient radiation exposure was significantly higher with the radiation-attenuating glove compared to the needle holder (8.43 vs 7.03 mSv; p = 0.027). Though radiation-attenuating gloves decreased hand radiation dose by 37%, this came at the price of a 3% increase in patient exposure. In contrast, the needle holder reduced exposure to both the surgeon's hand by 65% and the patient by 14%. Thus, a well-designed low-density needle holder could optimize radiation safety for both surgeon and patient.

Quality Improvement of Surgical Team Communication of Required Percutaneous Nephrolithotomy Equipment

OBJECTIVE

To evaluate if implementation of a percutaneous nephrolithotomy (PCNL) equipment whiteboard can improve communication accuracy of surgical equipment, streamline operative efficiency, and decrease unnecessary case equipment costs.

METHODS

A real-time editable equipment whiteboard was designed and implemented for all PCNL cases between October and December 2021. The relative difference in pre- and post-intervention surgical equipment accuracy as well as overall case costing was compared from 90 days prior to implementation to the period after intervention.

RESULTS

Quality assessment surveys were completed prior to whiteboard implementation (N = 25) and cost implementation (n = 15). Pre- and postoperative assessment of equipment communication, assessed on a 10-point scale, improved after implementation of the communication whiteboard (Pre-op: 6.7/10 vs. 8.9/10, P < .001. Post-op: 7.0/10 vs. 9.3/10, P < .001). On average 64% (3.2/5) of items were accurate on preintervention cases. Postintervention accuracy improved to 88% (4.4/5 items) (P = .049). There was a significant relative case cost improvement after implementing the PCNL equipment whiteboard with an average of $436.81 USD savings per case (P = .001) and $488.22 USD per renal moiety (P = .002).

CONCLUSION

Our baseline quality assessment of surgical team communication regarding PCNL equipment identified an area for improvement. Multidisciplinary feedback resulted in the development of a real-time editable PCNL equipment whiteboard which improved team perception of equipment communication, case item accuracy and resulted in a relative average cost savings for PCNL.

A mathematical method to estimate angle and distance for percutaneous renal puncture based on computed tomography data: Description and validation

Introduction

Gaining access to the kidney is crucial step in percutaneous nephrolithotomy (PCNL); it has a steep learning curve.

Objective

Describe the mathematical method to predict renal puncture angle and distance based on preoperative computed tomography (CT) measurements. Then evaluating how it correlates with measured values.

Patients and Methods

The study was prospectively designed. After ethical committee approval, the study uses data from preoperative CT to construct a triangle so we can estimate puncture depth and angle. A triangle of three points, the first is point of entry to the pelvicalyceal system (PCS), the second is point on the skin perpendicular to it, and the third where the needle punctures the skin. The needle travel is estimated using the Pythagorean theorem and puncture angle using the inverse sine function. We evaluated 40 punctures in 36 PCNL procedures. After PCS puncture using fluoroscopy-guided triangulation, we measured the needle travel distance and angle to the horizontal plane. Then compared the results with mathematically estimated values.

Results

We targeted posterior lower calyx in 21 (70%) case. The correlation between measured and estimated needle travel distance with Rho coefficient of 0.76 with P < 0.001. The mean difference between the estimated and the measured needle travel was - 0.37 ± 1.2 cm (-2.6-1.6). Measured and estimated angle correlate with Rho coefficient of 0.77 and P < 0.001. The mean difference between the estimated and the measured angle was 2° ± 8° (-21°-16°).

Conclusion

Mathematical estimation of needle depth and angle for gaining access to the kidney correlates well with measured values.

A pilot clinical study of developing an External Assist Targeting Device for rapid and precise renal calyx access during percutaneous nephrolithotomy

Objective

To design a device to increase the accuracy of the targeting process and reduce the radiation exposure to both the patients and the medical staff.

Methods

We analyzed the inherent problem and designed the External Assist Targeting Device (EATD) to assist in the alignment of needle targeting on the desired renal calyx under fluoroscopic guidance. The EATD was designed to allow rapid and precise access to calyces at all angles, with a simple two-step puncture protocol developed for puncturing a target renal calyx. We then tested the device in a pilot human trial with four patients.

Results

In experiments with phantom models, the time for successful targeting was reduced by 31% using the device. The mean fluoroscopic time was reduced by 40%. In initial human trial, the puncture time was shortened by 66% and the radiation dose was decreased by 65% compared to free-hand technique. No complication was observed during the trial.

Conclusion

The EATD was found to be cost effective, portable, simple to set up, and safe to operate for assisting in the percutaneous nephrolithotomy procedures. Our preliminary tests showed high degree of accuracy in gaining precise access to a targeted renal calyx with much shorter time and lesser radiation dose. The EATD also has the potential to be used to access other organs with precision under fluoroscopic guidance.

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.

Air vs contrast pyelogram for initial puncture access in percutaneous nephrolithotomy: a randomized controlled trial

Percutaneous nephrolithotomy (PCNL) is a standard procedure for large renal stones. Contrast (traditionally) as well as air is being used to delineate pelvi-calyceal system (PCS) to perform initial puncture. Contrast, when used has certain disadvantages including poor differentiation of anterior and posterior calyces. In this interim analysis of 122 patients of a prospective study subjects were stratified in two groups: in group 1, contrast was used while in group 2, air was used to delineate PCS. Out of 122,103 patients underwent puncture by contrast or air exclusively while 19 patients required mix of contrast and air (14 patients failed puncture using contrast while 5 using air). Mean dosage of radiation exposure (8.43 vs. 14.26 mGy), duration of radiation exposure (0.66 vs. 1.02 min), access time (3.72 vs. 5.84 min), were less in group 2 as compared to group 1. 84.5% of patients underwent puncture in single attempt in group 2 as compared to 56.25% in group 1. Five patients had post-operative fever and one had trans-pleural tract dilation. Complete stone clearance was seen in 94.8% of patients using air to only 75% of patients using contrast. Conclusion: Air pyelogram is a feasible, safe, cost effective and efficient access alternative to contrast pyelogram and in difficult situation a mixture of both is better than using one.

Trigonometric Concept of Fluoroscopy-Guided Percutaneous Renal Access

Percutaneous nephrolithotomy is the standard surgical management of large renal calculi. Percutaneous renal access using the triangulation method has been an enigma for the endourologist to master and teach. This surgical conundrum is due to the uncertainty in the angle and depth required to puncture the target calyx. We describe a novel trigonometric method of renal access where both the angle and the depth of puncture are easily determined before the puncture.