Intraoperative cone beam computed tomography for detecting residual stones in percutaneous nephrolithotomy: a feasibility study

Intraoperative Cone Beam Computed Tomography Increases Single Procedure Stone-Free Rates in Percutaneous Nephrolithotomy: Results of a Randomized Controlled Trial

Introduction: Achieving a stone-free status during percutaneous nephrolithotomy (PCNL) is crucial to prevent additional morbidity or stone growth. Cone beam computed tomography (CBCT) in a hybrid operating room provides intraoperative imaging of the urinary tract, improving stone-free status assessment and enabling additional stone extraction. This study aimed to determine whether intraoperative CBCT leads to increased stone-free rates (SFR) after PCNL. Materials and Methods: We conducted a two-arm randomized trial involving adult patients undergoing PCNL at a tertiary referral center for complex kidney stone treatment. Intraoperative randomization took place when the kidney was deemed endoscopically stone free. Patients were assigned to either undergo an intraoperative CBCT scan or be placed in a control group, in which the procedure was ended without a CBCT scan. All patients underwent a low-dose noncontrast abdominal CT scan 4 weeks postoperatively. The primary outcome measure was the stone-free status evaluated by this scan. Results: This trial was prematurely terminated because of reaching the predefined criteria for superiority upon interim analysis, with 160 randomizations up to this point. SFR was 15% higher in the CBCT group (76% vs 61%, p = 0.04) using a 4-mm cut-off. With a 2-mm cut-off, the SFR difference was 14% (58% vs 44%, p = 0.08). Using a 0-mm cut-off, the difference was 9% (50% vs 41%, p = 0.27). Residual fragments were identified in 56% of CBCT scans, with additional extraction in 49% of these cases. No significant difference in 30-day postoperative complications was observed. Conclusion: Intraoperative CBCT during PCNL significantly increases single procedure SFR. Trial registration: Netherlands Trial Register (NTR) NL8168, ABR NL70728.042.19. Prospectively registered on 15 October 2019.

Optimization of Cone Beam Computed Tomography Scan Protocols for the Intraoperative Detection of Residual Stones in Percutaneous Nephrolithotomy

Purpose: The primary surgical treatment modality for large or complex renal stones is percutaneous nephrolithotomy (PCNL). Cone beam computed tomography (CBCT) allows for intraoperative imaging and can be used to enhance intraoperative assessment of a stone-free status during a PCNL procedure. However, scanning protocols have not yet been optimized for this purpose. The high degree of stone and patient characteristics require a tailored approach. This study aimed to select the most suitable CBCT protocols for imaging stone fragments intraoperatively during PCNL. Methods: A phantom insert with 100 calcifications varying in size and density was placed in an anthropomorphic abdominal phantom. Nine different CBCT protocols were used with varying dose and copper filter settings, and each scan was repeated five times with a small translation between each scan. Detectability of the calcifications was scored by visual assessment and visibility curves were generated for each protocol, depicting the minimum size and density at which calcifications were still detectable. Image noise and contrast-to-noise ratios (CNRs) were calculated for each protocol, as well as estimated effective patient doses per CBCT scan. Results: Calcification detectability and CNRs decreased with a decrease in radiation dose, whereas noise ratios increased. Three suitable scanning protocols were selected, a high-dose or soft-stone CBCT protocol resulting in an effective dose of 10.7 millisievert (mSv) per CBCT scan, a medium-dose CBCT protocol resulting in an effective dose of 4.6 mSv and a low-dose or hard-stone CBCT protocol resulting in an effective dose of 2.2 mSv. Conclusion: Radiation dose for intraoperative CBCT for imaging calcifications can effectively be lowered while maintaining calcification visibility, by implementing low-dose CT protocols with lowered dose settings and the application of a copper filter. The three proposed scanning protocols provide options to select a scan protocol based on stone type and patient characteristics.

Intraoperative computed tomography for detection of residual stones in endourology procedures: systematic review and meta-analysis

BACKGROUND

Success rates in endourological procedures, notably percutaneous nephrolithotomy (PCNL) and ureteroscopy (URS), have demonstrated suboptimal outcomes, leading to more reinterventions and radiation exposure. Recently, the use of intraoperative computed tomography (ICT) scans has been hypothesized as a promising solution for improving outcomes in endourology procedures. With this considered, we conducted a comprehensive systematic review and meta-analysis encompassing all available studies that evaluate the impact of the use of intraoperative CT scans on surgical outcomes compared to conventional fluoroscopic-guided procedures.

METHODS

This systematic review was conducted in accordance with PRISMA guidelines. Multiple databases were systematically searched up to December of 2023. This study aimed to directly compare the use of an ICT scan with the standard non-ICT-guided procedure. The primary endpoint of interest was success rate, and the secondary endpoints were complications and reintervention rates, while radiation exposure was also evaluated. Data extraction and quality assessment were performed following Cochrane recommendations. Data was presented as an Odds ratio with 95%CI across trials and a random-effects model was selected for pooling of data.

RESULTS

A comprehensive search yielded 533 studies, resulting in the selection of 3 cohorts including 327 patients (103 ICT vs 224 in non-ICT). Primary outcome was significantly higher in the experimental group versus the control group (84.5% vs 41.4% respectively, 307 patients; 95% CI [3.61, 12.72]; p<0.00001; I2=0). Reintervention rates also decreased from 32.6% in the control to 12.6% in the ICT group (OR 0.34; 95%CI [0.12,0.94]; p =0.04; I2= 48%), whereas complication rates did not exhibit significant differences. Radiation exposure was also significantly reduced in two of the included studies.

CONCLUSION

This meta-analysis highlights a favorable outcome with intraoperative CT scan use in PCNL procedures, showing a considerable increase in SFR when compared to standard fluoroscopy and nephroscopy. Despite limited studies, our synthesis underscores the potential of ICT scans to significantly reduce residual stones and their consequences for endourology patients, as reinterventions and follow-up ionizing radiation studies.

Cone Beam Computed Tomography-Assisted Percutaneous Nephrolithotomy in a Hybrid Operating Room: Optimization of Patient Selection

Background: Cone beam computed tomography (CBCT) enables intraoperative cross-sectional and three-dimensional imaging of the urinary tract. CBCT in a hybrid operating room can be used for intraoperative detection of residual stones and potential additional stone extraction at the end of percutaneous nephrolithotomy (PCNL). This study describes our initial experience with intraoperative CBCT during PCNL and analyzes its role in potentially improving its outcomes. Methods: We conducted a single-center retrospective cohort study at a tertiary referral hospital between 2018 and 2021. The study aimed to evaluate the outcome of patients who underwent intraoperative noncontrast CBCT scan during PCNL. The CBCT scan was performed when the urologist determined the kidney to be endoscopically stone-free. In case any residual fragments were imaged, an additional effort was made to extract them. Patients were divided into three groups based on treatment outcome: stone-free upon CBCT, not stone-free with additional stone extraction after CBCT, and not stone-free without additional stone extraction. Procedure and patient characteristics were recorded to identify factors associated with additional stone extraction during CBCT-assisted PCNL. Results: A total of 102 procedures were included in this study. Intraoperative CBCT scans showed residual calcifications in 58 (57%) cases. In 39 cases, which is 38% of the total population and 61% of the cases with residual calcifications, one or more residual fragments imaged on the intraoperative CBCT-scan were extracted additionally within the same procedure. A higher Guy's Stone Score was associated with a higher likelihood of additionally extracting stones as a result of the CBCT. Conclusions: CBCT-assisted PCNL in a hybrid operating room can lead to additional stone extraction in the same procedure in 37% of all cases and in over 60% of the cases in which residual fragments are imaged. The value of CBCT-assisted PCNL appears to increase in the case of more complex stone surgery cases.

Ultralow-Dose Intraoperative Computed Tomography During Endoscopic Stone Surgery: A Quality Improvement Project

Objectives: To improve care in patients with large kidney stones using advanced intraoperative imaging techniques to reduce perioperative radiation exposure, improve stone-free rates (SFRs), and reduce the number of surgical interventions in a quality improvement project. Patients and Methods: Patients with kidney stones appropriate for percutaneous nephrolithotomy (PCNL) treatment were scheduled into a hybrid operating room for endoscopic surgery (PCNL and/or ureteroscopy) with intent to perform intraoperative CT (ICT). Imaging was performed using an Artis Zeego Care+Clear™ (Siemens) robotic-armed multiplanar fluoroscopy system with collimation to the level of the affected kidney(s). After the initial case, the proprietary CARE™ (combined applications to reduce exposure) protocol was used. When the hybrid room was unavailable, a mobile CT scanner (O-Arm; Medtronics) was used in the traditional room (n = 2). Results: Thirty-one ICTs were performed in 23 consecutive patients during endoscopic stone procedures with a median effective radiation dose of 1.39 mSv per scan, significantly less than the preoperative noncontrast CT (12.02 mSv) in the same patients (p < 0.001). Longitudinal radiation exposure associated with stone treatment significantly decreased by 83% (15.80 to 2.68 mSv, p < 0.001) compared with a similar historical PCNL cohort. Clinically significant residual stones (≥3 mm) were identified at initial ICT in eight patients (35%) and further treated in six patients. One patient had missed residual stone diagnosed 34 days after surgery, which was apparent on re-review of the ICT. Thus, final verified SFR was 87% for all stages. Mean number of procedures improved from 1.77 to 1.30 (p = 0.05) and rate of postoperative CT scans improved from 82% to 26% (p < 0.001). Conclusion: Ultralow-dose ICT was demonstrated to simultaneously improve SFR and number of staged treatments, and greatly reduce the perioperative radiation dose for our patients. The findings support the continued use of this modality to benefit all patients with large stones.

Cone beam computed tomography for detecting residual stones in percutaneous nephrolithotomy, a randomized controlled trial (CAPTURE) protocol

Introduction

Percutaneous nephrolithotomy (PCNL) is the standard surgical treatment method for large kidney stones. Its aim is to achieve a stone-free status, since any residual fragments (RFs) after PCNL are likely to cause additional morbidity or stone growth. Enhancing intraoperative detectability of RFs could lead to increased stone-free rates and decreased re-intervention rates. Cone beam computed tomography (CBCT) has recently been introduced in urology as a feasible method for intraoperatively imaging RFs. The aim of this trial is to determine the added value of CBCT in percutaneous nephrolithotomy, by measuring differences in stone-related morbidity for patients with procedures in which a CBCT is used versus patients with procedures without the use of CBCT.

Methods

The CAPTURE trial is an investigator-initiated single-center, randomized controlled trial (RCT) in adult patients who have an indication for percutaneous nephrolithotomy. A contemporary percutaneous nephrolithotomy is performed. Once the surgeon is convinced of a stone-free status by means of fluoroscopy and nephroscopy, randomization allocates patients to either the study group in whom an intraoperative CBCT scan is performed or to the control group in whom no intraoperative CBCT scan is performed. The main endpoint is the stone-free status as assessed four weeks postoperatively by low-dose non-contrast abdominal CT, as a standard follow-up procedure. Secondary endpoints include the number of PCNL procedures required and the number of stone-related events (SREs) registered. The total study population will consist of 320 patients that undergo PCNL and are eligible for randomization for an intraoperative CBCT scan.

Discussion

We deem a randomized controlled trial to be the most effective and reliable method to assess the efficacy of CBCT in PCNL. Though some bias may occur due to the impossibility of blinding the urologist at randomization, we estimate that the pragmatic nature of the study, standardized circumstances, and follow-up methods with pre-defined outcome measures will result in a high level of evidence.

Trial registration

Netherlands Trial Register (NTR) NL8168, ABR NL70728.042.19. Registered on 15 October 2019. Prospectively registered.

The Intraoperative Use of a Portable Cone-Beam Computed Tomography System for the Diagnosis of Intraperitoneal Bladder Perforation

Background

Intraoperative imaging for endourologic procedures is generally limited to single-plane fluoroscopic X-ray. The O-arm™ is a mobile cone-bean CT scanner that may have applications in urologic surgeries. Case Presentation. We present a case of an 85-year-old male with radiation cystitis and recurrent gross hematuria who was identified to have a bladder perforation on cystoscopy during emergent clot evacuation. Single-view fluoroscopic evaluation was inconclusive as to whether an intraperitoneal bladder perforation occurred. A portable cone-beam CT scan was used to acquire a 3-D CT cystogram, which demonstrated intraperitoneal contrast extravasation, confirming the diagnosis of an intraperitoneal bladder perforation.

Conclusion

We report the first use of a portable cone-beam CT scanner to perform an intraoperative CT cystogram to diagnose an intraperitoneal bladder perforation and guide surgical management.