Abu Dhabi, United Arab Emirates (UroToday.com) Dr. Thomas Chi speaks on the “perfect puncture” for percutaneous nephrolithotomy (PCNL). He focuses on the basics, which always starts with equipment. The image guidance modality of either ultrasound, fluoroscopy, or a combination of the two. The use of an ultrasound friendly echo tip needle can increase visibility and improve ease of access. Wires can vary greatly and Dr. Chi says “whatever wire you choose should get you what you want”.   PCNL position is broadly broken up into supine vs prone, but even within both approaches, there are a number of variations. Regardless of position and approach, the key landmarks for successful percutaneous renal access are the same: 11th and 12th ribs, iliac crest, and the paraspinous muscles form the borders of the window of access.

For Dr. Chi’s supine PCNLs, he prefers the Galdakao-Modified Valdivia position with hips and shoulders bumped up, lithotomy with stirrups, ipsilateral arm across the chest, and patient on side of the table. Regardless of the approach, accessing the correct renal calyx is paramount as this decreases blood loss and increases stone clearance rate. In fluoroscopic access, the correct calyx is ALWAYS posterior, however, ultrasound access may vary.

For fluoroscopy access, they can be broken up into 4 categories: monoplanar, biplanar long axis, biplanar perpendicular axis, and triangulation with common keywords: “Bullseye technique” and “triangulation”. The understanding of the ideal access tract stems from renal anatomy. Based on CT reconstructions – upper pole calcyes are oriented in medial/lateral while the inferior calyces are oriented anterior/posterior. Dr. Chi’s lower pole access follows an important rule; that is, the lower pole access should almost always aim to go through “door number 2”. “Door number 2” referring to not the most inferior lower pole calyx, but the second most inferior (or one calyx superior to the lowermost calyx).

In regards to ultrasound-guided access, he breaks it down to 2 essential skills. First is the impeccable and reproducible renal ultrasound image. Second is the ability to bring the needle into the image. The combination of the two will lead the way to the perfect ultrasound guidance. After all, ultrasound guidance has the benefits of visualization of peri-renal structures, less expensive, and lower radiation exposure. Furthermore, ultrasound has a relatively lower learning curve at approximately 20 cases, while fluoroscopic guidance takes approximately 60 cases to be competent. It is also important for urologists to understand when to ask for help. In aberrant anatomy with ectopic kidneys (pelvic, thoracic), malrotated kidneys, or surrounding viscera, ask your interventional radiologists for CT guided access.

In conclusion, perfect access requires the urologist to choose wisely, taking into consideration his or her own skillset as well as the goals of the surgery.

Presented by: Thomas Chi, MD, UCSF Department of Urology, University of California, San Francisco, California 

Written by Pengbo Jiang, MD, Department of Urology, University of California, Irvine, California at the 37th World Congress of Endourology (WCE) – October 29th-November 2nd, Abu Dhabi, United Arab Emirates