In percutaneous lithotripsy, where is the ultrasonic probe inserted?

• A. Through a nephrostomy tube into the renal pelvis
• B. Through the urethra into the bladder
• C. Through the abdomen into the peritoneal cavity
• D. Through the skin over the flank into the kidney tissue

Answer: (A)

Percutaneous lithotripsy accesses stones by creating a small tract from the skin into the kidney’s collecting system, usually via a flank approach. The ultrasonic probe is advanced along this percutaneous tract into the renal pelvis (and calyces) to fragment the stone directly inside the kidney. A nephrostomy tube is often left in place after the procedure to drain urine and maintain access, so the ultrasonic probe is effectively inserted through this nephrostomy channel into the renal pelvis. This approach differs from going through the urethra into the bladder or entering the abdomen/peritoneal cavity, which are not the routes used for percutaneous stone fragmentation.