V9-09: Navigation System in Percutaneous Nephrolithotripsy
VideoIntroductions and Objectives
Percutaneous Nephrolithotripsy (PCNL) is a common procedure in urology to remove renal stone. Traditionally fluoroscopy or ultrasonography (USG) or both is used for guiding the track creation during the procedure. However the fluoroscopy usage means radiation exposure to both patient, surrounding assistant and surgeons. Therefore we should cut down the radiation exposure as much as possible. Although tradition USG guidance will serve the purpose, it is difficult to visualize the needle track during screening and hence lack of predictability and sense of security, particularly when the calyceal system is not dilated. It is also difficult to learn and most of the times multiple passes are required which increase the risk of hematoma formation. Hence the objective of using USG with navigation system was to solve the above problems.
The magnetic field-based navigation USG can visualize the position of the needle track in relation to the target calyx. Its predicted future pathway is sensed, transformed into two-dimensional graphics, and overlaid onto the USG image in real time. The localizing system comprises two sensors, one inside the needle and one attached to the USG probe. The magnetic field is created by a magnet placed closely to the operative field. The navigation device supports interventions in plane, with the needle constantly in the image plane, or out of plane, with the needle aiming from outside the imaging plane at a target. Procedures performed in the image enable visual control of the needle insertion throughout the procedure. Needle deviation and injury of neighboring structures can be detected immediately.
Target calyceal system with stone inside can be puncture precisely and safely with single pass. The posterolateral approach was chosen during track creation to avoid inadvertent injury of the interlobar arteries, which are located laterally to the papillae within the parenchyma and to improve fixation of the nephrostomy sheath.
USG with navigation system can provide radiation free guidance of creating track in PCNL. It is predictable, precise, reliable and safe. Most importantly the technique is easy to learn particularly for urologist who is new to PCNL.