Lithotripsy Health Article

Definition

Lithotripsy is a therapeutic medical procedure used to disintegrate stones (calculi) in the urinary tract and kidneys. Extracorporeal shock wave lithotripsy (ESWL) uses shock waves generated outside the body and is non-invasive. Intracorporeal shock wave lithotripsy (ISWL) delivers shock waves through a specially designed scope used for the urinary tract (ureteroscope) and kidneys (nephroscope) and is a minimally invasive procedure. Ultrasound lithotripsy also uses a scope to deliver ultrasonic waves (mechanical vibrations) and is minimally invasive.

Purpose

Lithotripsy is used when a kidney stone is too large to pass on its own, or when a stone becomes stuck in a ureter (a tube which carries urine from the kidney to the bladder) and will not pass. Kidney stones are extremely painful and can cause serious medical complications, such as kidney damage, if not removed. Usually, stones smaller than 5 mm in diameter can pass without intervention, while stones larger than 7 mm in diameter require lithotripsy or the placement of a urethral or ureteral stent to help them pass. Stones larger than 10 mm require lithotripsy or surgery.

ESWL is a noninvasive alternative to open surgery (which is only very rarely performed for stones now) or percutaneous nephrolithotomy. ESWL is used in patients with stones less than or equal to 1 cm located in the kidneys or ureters. ISWL is a minimally invasive endoscopic technique that is used in patients with stones over 1 cm, with stones in the lower urinary tract, with impacted stones, and when ESWL is unsuccessful. Both ESWL and ISWL can also be used to fragment gallbladder and bile duct stones.

Precautions

ESWL should not be considered for patients with severe skeletal deformities, patients weighing over 300 lbs (136 kg), patients with abdominal aortic aneurysms, or patients with uncontrollable bleeding disorders. Patients who are pregnant should not be treated with ESWL. Patients with cardiac pacemakers should be evaluated by a cardiologist familiar with lithotripsy. Lithotripsy may temporarily inhibit the pacemaker or cause circuit damage leading to erratic functioning or cessation of the pacemaker. The cardiologist should be present during the lithotripsy procedure in the event there are problems with the pacemaker.

Description

Lithotripsy uses focused shock waves to fragment a stone in the kidney or the ureter. In ESWL, the patient is placed on a table in contact with a water-filled cushion; and a shock wave is generated, travels through the water, and shatters and fragments the stone. Older ESWL systems involved immersing the patient in a tub of water; but this space-consuming, awkward method has been replaced by water-filled cushions. Once the stone is fragmented, the resulting gravel is left to pass on its own; the patient may have been stented prior to the procedure to widen the urethra and or ureters to allow the fragments to pass easily and with less pain. In ISWL, a ureteroscope is inserted through the urethra and bladder and into the ureters, or a nephroscope is inserted, usually through an incision in the patient's back. Once the stone is located using the endoscope, an electrohydraulic, laser, or ultrasound lithotripter can be used to fragment the stone. In ISWL using an electrohydraulic lithotripter, a probe is inserted through the endoscope and against the stone, and shock waves are delivered by a generator. In laser ISWL,

a pulsed-dye laser is used to deliver laser energy through a fiber inserted through the endoscope and into the stone. Ultrasound ISWL uses a generator to produce mechanical vibrations delivered to the stone via a probe tip inserted through the generator. In ISWL, after the stone is fragmented, the pieces can be removed using a grasper or basket or left to pass on their own if they are small enough.