Robot‐assisted fluoroscopy‐guided renal puncture for endoscopic combined intrarenal surgery: a pilot single‐centre clinical trial

Abstract

The development of new and improved endoscopic devices has led to percutaneous nephrolithotomy (PCNL) being widely used to treat large renal stones [1]. Although this technique provides a high stone-free rate (SFR), it is also associated with various complications, e.g. bleeding, urosepsis, and thoracic/abdominal injuries, which are mainly related to renal access. Thus, even during endoscopic combined intrarenal surgery (ECIRS), renal access and especially papillary puncture should be guided using ultrasonography (US) or fluoroscopy, which requires a fair amount of training to master [2]. A new strategy involves electromagnetic guidance through a ureteroscope to achieve retrograde puncture of the renal papilla [3]. These techniques can allow even inexperienced surgeons to achieve proper renal access, although manual adjustment of the puncture remains a challenging step. Robotic percutaneous access to the kidney was first introduced in 2002 [4] and an automated needle target with X-ray (ANT-X) has been developed for navigating renal puncture during PCNL [5]. The software uses artificial intelligence to determine the optimal trajectory for needle puncture using a single-shot fluoroscopic image and a calculation of the distances between the robot-arm markers and the needle tip location on the patient’s skin. We have evaluated the safety and efficacy of ANT-X for renal puncture in a bench-top study using a phantom kidney model and subsequently during ECIRS [6]. Based on the preliminary results indicating that the ANT-X process was potentially useful, we designed a pilot study to investigate the clinical safety and feasibility of robot-assisted fluoroscopy-guided (RAF)-ECIRS. The present single-centre single-arm pilot study was conducted at the Nagoya City University Hospital between January 2020 and June 2020. The study protocol was approved by the Institutional Review Board (#2019A002) and registered in the Japan Registry of Clinical Trials (#jRCTs042190074). All subjects provided informed consent prior to enrolment. We recruited patients who were aged 16–80 years, had large renal stones (diameter >15 mm), and had requested miniaturised ECIRS. We excluded patients if they were pregnant women, had an active UTI, were undergoing anti-platelet/coagulation therapy, or general anaesthesia was considered difficult by the anaesthesiologists. The primary endpoints were SFR at 3 months after the procedure and the rate of successful renal puncture. The secondary endpoints included the renal puncture time, fluoroscopy time, total operation time, and perioperative complications. The SFR was calculated as the number of cases with no residual fragments that were >3 mm, based on CT findings. All RAF-ECIRS procedures were performed by a single surgeon (K.T.) who had never performed a procedure that involved fluoroscopy-guided renal access. During the procedures, the patients were positioned in the prone split-leg position under general anaesthesia. A flexible ureteroscope was inserted through a ureteric access sheath and the contrast medium was injected from the ureteroscope to fluoroscopically visualise the renal collecting system. The surgeon then initiated the PCNL by mounting the robot-arm on the patient and marking the needle tip point on the patient’s skin based on the fluoroscopic image of the renal collecting system. The software determined the optimal trajectory for calyx puncture using the fluoroscopic image and the needle was inserted into the targeted calyx from the tilted C-arm view. The insertion was also guided by fluoroscopy and ureteroscopy if possible. The details of RAF renal access are illustrated in Fig. 1. The rest of the procedure was continued using a 16.5/17.5-F percutaneous tract with a 12-F nephroscope (Karl Storz, Tuttlingen, Germany) and pneumatic lithotripter. Despite the coronavirus pandemic, we enrolled 19 patients during the 6-month study period, including 14 men and five women. The mean age was 55 years and the