Microperc' is a recently described technique in which percutaneous renal access and lithotripsy are performed in a single step using a 16 G micropuncture needle. 'Mini-microperc' is a further technical modification in which an 8 Fr sheath is used to allow insertion of ultrasonic or pneumatic lithoclast probe with suction. The available evidence indicates that microperc is safe and efficient in the management of small renal calculi in adult and pediatric population. It can also be used for renal calculi in ectopic kidneys and bladder calculi. The high stone clearance rate and lower complication rate associated with microperc make it a viable alternative to retrograde intrarenal surgery.
The procedure is usually carried out under general anesthesia. However, it can be performed under regional anesthesia if required. In lithotomy position, a 7 Fr ureteric catheter is placed through the ureter into the renal pelvis under cystoscopic and fluoroscopic guidance. Multiple side holes are made in the distal 5 cm of the ureteric catheter to improve the drainage and prevent clogging by stone fragments and blood clots. The ureteric catheter is fixed to 16 Fr urethral catheter and the patient is turned to prone position.
The pelvicalyceal system is gently filled with saline injected retrograde through the ureteric catheter. This creates a mild hydronephrosis, which aids in ultrasound-guided calyceal puncture. The 16 G microperc puncture needle is placed into the puncture guide attachment. The use of this attachment facilitates percutaneous renal access. An ideal puncture would be one that leads straight from the skin puncture site through a papilla and the target calyx into the renal pelvis along the line of the infundibulum. Usually, the stone containing calyx is targeted; if the stone is in the renal pelvis, either middle or lower calyceal puncture is preferred. Once proper puncture is achieved, the stylet is removed and antegrade contrast study is performed. If required, the puncture can be adjusted at this step under fluoroscopic guidance. However, puncture can also be achieved with fluoroscopic guidance, wherein contrast is injected from ureteric catheter and percutaneous renal access achieved.