A noninvasive procedure for removing obstructive renal calculi or gallstones, extracorporeal shock-wave lithotripsy (ESWL) uses high-energy shock waves to break up calculi and allow their normal passage. In this treatment, the patient is anesthetized. His affected kidney or the area containing the gallstone is positioned over an electric spark generator, which creates high-energy shock waves that shatter calculi without damaging surrounding tissue. Afterward, the patient is easily able to excrete the fine gravel-like remains of the calculi through the urinary tract or biliary ductal system.

ESWL may be performed as a preventive measure in a patient with potentially obstructive calculi or as an emergency treatment for an acute obstruction. Because ESWL is noninvasive, the procedure may be performed in the outpatient department, and the patient can resume normal activities immediately after discharge. ESWL also minimizes many of the potentially serious complications associated with invasive methods of calculi removal, such as infection and hemorrhage.

ESWL isn’t suitable for all patients, however. For instance, it may be contraindicated during pregnancy or in a patient with a pacemaker (because of potential electrical interference), with urinary or biliary tract obstruction distal to the calculi (which would prevent passage of fragments), with renal or gallbladder cancer, or with calculi that are fixed to the kidney, ureter, or gallbladder or located below the level of the iliac crest. Repeat treatments may be necessary for large or multiple calculi. (For information about another form of lithotripsy, see Understanding percutaneous ultrasonic lithotripsy.)