Abstract
To design a simple, cost-effective system for gaining rapid and accurate calyceal access during percutaneous nephrolithotomy (PCNL). The design consists of a low-cost, light-weight, portable mechanical gantry with a needle guiding device. Using C-arm fluoroscopy, two images of the contrast-filled renal collecting system are obtained: at 0-degrees (perpendicular to the kidney) and 20-degrees. These images are relayed to a laptop computer containing the software and graphic user interface for selecting the targeted calyx. The software provides numerical settings for the 3 axes of the gantry, which are used to position the needle guiding device. The needle is advanced through the guide to the depth calculated by the software, thus puncturing the targeted calyx. Testing of the system was performed on 2 target types: 1) radiolucent plastic tubes the approximate size of a renal calyx (5 or 10 mm in diameter, 30 mm in length); and 2) foam-occluded, contrast-filled porcine kidneys. Tests using target type 1 with 10 mm diameter (n=14) and 5 mm diameter (n=7) tubes resulted in a 100% targeting success rate, with a mean procedure duration of 10 minutes. Tests using target type 2 (n=2) were both successful, with accurate puncturing of the selected renal calyx, and a mean procedure duration of 15 minutes. The mechanical gantry system described in this paper is low-cost, portable, light-weight, and simple to set up and operate. C-arm fluoroscopy is limited to two images, thus reducing radiation exposure significantly. Testing of the system showed an extremely high degree of accuracy in gaining precise access to a targeted renal calyx.
Highlights
Since the first description of percutaneous nephrolithotomy (PCNL) by Fernström and Johansson more than 30 years ago, major technological advances have improved the efficacy and safety of this procedure, confirming its superiority compared to open surgery for renal calculi [1].Obtaining precise access to a predetermined renal calyx is the most critical part of PCNL [2]
This paper describes the development of a computer directed gantry system using C-arm fluoroscopy to gain rapid and accurate renal access during PCNL
Fourteen tests were performed in the operating room using the 10 mm diameter target type-1
Summary
Obtaining precise access to a predetermined renal calyx is the most critical part of PCNL [2]. Available techniques for obtaining percutaneous (PC) access to the renal collecting system include the following: Two-stage procedure: Pre-operative access is first obtained by an interventional radiologist using ultrasound guidance, after which the urologist dilates. A recent report indicates that the minority of urologists (11%) gain their own access for PCNL [3]. Retrograde percutaneous access: This involves retrograde placement of a ureteric catheter, followed by passage of a sharp wire through the catheter and via the selected calyx to the skin [4]. Despite the feasibility of this method, it offers no advantage over antegrade percutaneous access and is not commonly utilized
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