During lithotripsy, fragmentation of renal calculi is achieved by which method?

• A. Ultrasonic energy
• B. Laser energy
• C. Shock waves
• D. Mechanical crushing

Answer: (A)

Fragmentation is achieved by delivering high-energy acoustic pulses that focus on the stone. These shock waves generate rapid pressure changes and cavitation in the surrounding fluid, producing stresses that exceed the stone’s strength and cause it to fracture into smaller pieces that can pass spontaneously in the urine. This noninvasive approach—extracorporeal shock wave lithotripsy—is the primary method used to break renal calculi. Other modalities exist, such as ultrasonic energy used in different lithotripsy techniques, laser energy for endoscopic fragmentation, and mechanical crushing during invasive approaches, but the standard noninvasive fragmentation relies on shock waves.