Gel Rolls Increase Percutaneous Nephrolithotomy Radiation Exposure.

Introduction: Despite increasing interest in reducing radiation doses during endoscopic stone surgery, there is conflicting evidence as to whether percutaneous nephrolithotomy (PCNL) positioning (prone or supine) impacts radiation. We observed clinically that a patient placed prone on gel rolls had higher than expected radiation with intraoperative CT imaging and that gel rolls were visible on the coaxial imaging. We hypothesized that gel rolls directly increase radiation doses. Methods: Anthropomorphic experiments to simulate PCNL positions were performed using a robotic multiplanar fluoroscopy system (Artis Zeego Care+Clear, Siemens) and a 5-second coaxial imaging protocol (5s BODY). A fluoroscopy phantom was placed in various positions, including prone on a gel roll; prone on blankets of equal thickness; prone and supine directly on the table; and modified supine (MS) positions using a thin gel roll or rolled blanket. Impacts of C-arm direction and use of a 1 L saline bag were also evaluated. Measured dose area product (DAP) was compared for the groups. Results: Measured DAP was found to increase by 146 µGy*m2 (287%) when prone on gel rolls compared with only 62.29 (23%) when placed on blankets of equal thickness, although the model likely both overstates the relative impact and understates the absolute impact that would be seen clinically. Measured DAP between experimental groups also varied considerably despite fluoroscopy time being held constant. Conclusions: Our experiments support our hypothesis that gel rolls directly increase radiation dose, which has not been previously reported, using an anthropomorphic model. Surgeons should consider radiolucent materials for positioning to limit radiation exposure to patients and the surgical team.

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.

Carbon Dioxide Pyelography: A Convenient and Safe Alternative to Both Room Air and Iodinated Contrast Pyelography During Endourologic Procedures.

Introduction/Background: There are increasing reports of serious complications related to the air pyelography technique, which raise concerns about the safety of room air (RA) injection into the renal collecting system. Carbon dioxide (CO2) is much more soluble in blood than nitrogen and oxygen and thus considerably less likely to cause gas emboli. Iodinated contrast medium (ICM) is expensive, and supplies may not be as reliable as previously assumed. CO2 pyelography (CO2-P) techniques using standard fluoroscopy and digital subtraction fluoroscopy (CO2 digital subtraction pyelography [CO2-DSP]) are described. Materials and Methods: During the endourologic stone cases, 15 to 20 mL of CO2 gas was typically injected into the renal pelvis through a catheter or sheath. Imaging was usually obtained with endovascular CO2 digital subtraction angiography settings using either a traditional fluoroscopy system (TFS) or robotic arm multiplanar fluoroscopy system (RMPFS) (Artis Zeego Care+Clear®; Siemens). Results: CO2-P was performed in 22 endoscopic stone treatment cases between March 2021 and August 2022, primarily using digital subtraction settings in 20 cases. CO2-DSP overall provided higher quality images of the renal pelvis and collecting system than CO2-P, but with a relatively higher radiation dose. Following a quality intervention, fluoroscopy doses for CO2-DSP cases were decreased by 81% overall. The use of CO2-P avoided fluoroscopic or intraoperative CT (ICT) artifacts seen with intraluminal ICM. Conclusions: CO2-P allows the urologist to obtain imaging of the renal collecting system without ICM and with much lower risk of air embolism compared with RA pyelography. CO2 is a nearly cost-free alternative to ICM. Because CO2 is widely available and the technique is easy to perform, we propose that CO2-P should be favored over traditional air pyelography to improve patient safety.