PERCUTANEOUS NEPHROLITHOTOMY

Kidney stone treatment: percutaneous nephrolithotomy (PCNL)
Technique
PCNL is the removal of a kidney stone via a  track  developed between the surface of the skin and the collecting system of the kidney. The first step requires  inflation  of the renal collecting system (pelvis and calyces) with fluid or air instilled via a ureteric catheter inserted cystoscopically. This makes subsequent percutaneous puncture of a renal calyx with a nephrostomy needle easier. Once the nephrostomy needle is in the calyx, a guidewire is inserted into the renal pelvis to act as a guide over which the  track  is dilated. An access sheath is passed down the track and into the calyx, and through this a nephroscope can be advanced into the kidney. An ultrasonic lithotripsy probe is used to fragment the stone and remove the debris.

A posterior approach is most commonly used; below the 12th rib (to avoid the pleura and far enough away from the rib to avoid the intercostals, vessels, and nerve). The preferred approach is through a posterior calyx, rather than into the renal pelvis, because this avoids damage to posterior branches of the renal artery which are closely associated with the renal pelvis. General anaesthesia is usual, though regional or even local anaesthesia (with sedation) can be used.

Indications for PCNL
PCNL is generally recommended for stones >3cm in diameter, those that have failed ESWL and/or an attempt at flexible ureteroscopy and laser treatment. It is the first-line option for staghorn calculi,17 with ESWL and/or repeat PCNL being used for residual stone fragments.
For stones 2 - 3cm in diameter, options include ESWL (with a JJ stent in situ), flexible ureteroscopy and laser treatment, and PCNL. PCNL gives the best chance of complete stone clearance with a single procedure, but this is achieved at a higher risk of morbidity. Some patients will opt for several sessions of ESWL or flexible ureteroscopy/laser treatment and the possible risk of ultimately requiring PCNL because of failure of ESWL or laser treatment, rather than proceeding with PCNL  up front . ~50% of stones >2cm in diameter will be fragmented by flexible ureteroscopy and laser treatment.

Outcomes of PCNL
For small stones, the stone-free rate after PCNL is in the order of 90 - 95%. For staghorn stones, the stone-free rate of PCNL, when combined with post-operative ESWL for residual stone fragments, is in the order of 80 - 85%.