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Lithotripsy - How It Works

Science EncyclopediaScience & Philosophy: Linear expansivity to Macrocosm and microcosmLithotripsy - History, Lithotripsy And Kidney Stones, How It Works

How it works

A lithotripter generates shock waves by means of electrical or spark discharges within a spherical or ellipsoidal reflector submerged in water. Some waves propagate directly away from the curved surface of the reflector (primary shock waves). Others strike and bounce off the inner wall of the reflector (reflected shock waves).

In order to focus the shock waves so they pass into the body and strike kidney stones, physicians must first locate the stones by means of fluoroscopy or ultrasound.

During the treatment, there are a series of clicks that correspond to the shock waves passing through the water and body tissue to break up the stone. Treatment takes about one to two hours.

Many lithotripters require patients to be lowered into a water bath. Shock waves travel through the water and into the body. The procedure restricted the positioning of the patient so that only stones in the upper urinary tract were accessible to shock waves.

More recent lithotripters do not require patients to be lowered into a bath or to lie on a bed of water. Rather, the water is located inside the shock wave generator under the table on which the patient lies. This keeps the patient and water apart, permitting doctors to more easily position patients on the table to treat kidney stones, and increases the ability of physicians to target and destroy them.

ESWL does not damage the kidney, so the physician can repeat the procedure if necessary. Most patients can return home the same day of treatment.

In some patients, a stone may be able to be seen only after a narrow tube called a stent is placed in the ureter. The patient is first put under anesthesia. Then the physician inserts a thin, narrow light tube called a cystoscope into the urethra to help guide placement of the stent. The stent is removed after treatment.

Following treatment, the patient may feel an ache in the lower back, and may have some discomfort passing the remains of the stones. In addition, there is often blood in the urine.

The treatment is not recommended for everyone. For example, women who are pregnant and individuals who already have urinary tract infections should not undergo ESWL.

Marc Kusinitz

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