Indications - Patients with kidney and/or ureteral stones may be candidates for shock wave lithotripsy. Contraindications to patients undergoing this procedure are pregnancy and unresolved infection. If the stone measures greater then 2centimeters, shock wave lithotripsy may not be the best initial treatment. In stones located in the lower part of the ureter shock wave lithotripsy may be a inadequate and is not a first choice for women of child bearing age.
Procedure - The patient lies flat on the lithotripsy table or partially submerged in a water bath in older models. The lithotriptor is then targeted to the stone using fluoroscopy, a low radiation energy. The stone is fragmented by high-energy shock waves that are generated outside of the body. Shock waves travel through the body very much like sound waves. The energy of the shock waves is delivered to the stone in focus and not to the surrounding tissue. The stone is fragmented to particles of a size that can pass spontaneously. An incision to remove the stone is thus avoided. It certain cases an internal stent is required temporarily to enhance stone passage and prevent obstruction from impacted stone fragments.
Results - The results of ESWL depend on the size of the stone, stone burden, type of stone, and location. In general ESWL is used for stones less than 1 to 2 centimeters in size. Most stones fracture well with ESWL treatment. Hard stones such as calcium oxalate monohydrate and cystine stones are more difficult to break with ESWL and therefore often require percutaneous nephrostolithotomy. Fragments from stones located higher within the collecting system are more likely to pass spontaneously than stones in the lower portion of the kidney, simply due to gravitational effect. Stones larger than 1 to 2 centimeters or hard stones will often require multiple ESWL treatments to entirely rid the kidney of all stone fragments.
