A lithotriptor is a medical device used in the non-invasivetreatment of kidney stones(urinary calculosis) and biliary calculi(stones in the gallbladderor in the liver). The scientific name of this procedure is Extracorporeal Shock Wave Lithotripsy (ESWL). Lithotripsy was developed in the early 1980s, and came into widespread use with the introduction of the HM-3 lithotriptor in 1983. Within a few short years, ESWL revolutionized treatment of calculosis. It is estimated that more than one million patients are treated annually with ESWL in the USA alone.
How it works
Lithotripsy attempts to break up the stones with minimal collateral damage by using an externally-applied, focused high-intensity acoustic pulse.
The sedatedor anesthesizedpatient lies down in the apparatus' bed, with his back supported by a water-filled coupling device placed at the level of kidneys, for instance. A fluoroscopicx-rayimaging system or an ultrasoundimaging system are used to locate the stone and aim the treatment head such that the F1 of the shock wave is focused upon the offending stone. The treatment usually starts at the equipment's lowest power level, with a long gap between pulses, in order to acustom the patient to the sensation. The frequency of pulses & power level will then be gradually increased, in order to break up the stone more effectively. The final power level will usually depend on the patient's pain threshold. If the stone is positioned near a bone (usually a rib in the case of kidney stones), then this treatment may be more uncomfortable as the shock waves can cause a mild resonance in the bone which can be felt by the patient.
The successive shock wave pressure pulses result in direct shearing forces, as well as cavitation bubbles surrounding the stone, which fragment the stones in smaller pieces, which then can pass easily through the uretersor the cystic duct. The process takes about an hour. A ureteral stent(a kind of expandable hollow tube) may be used at the discretion of the urologist. The stent allows for easier passage of the stone by relieving obstruction, and through passive dilatation of the ureter.
Extracorporeallithotropsy works best with stones between 4 mm and 2 cm in diameter, that are still located in the kidney. It can be used to break up stones which are located in a ureter, too, but with less success.
The patient undergoing this procedure can, in some cases, see for themselves the progress of their treatment. If allowed to view the ultrasound or x-ray monitor, they may be able to see their stone change from a distinct bright point, to a fuzzy cloud, as the stone is disintegrated into a fine powder.
ESWL is the least invasive of the commonplace modalities for definitive stone treatment, but provides a lower stone-free rate than other more invasive treatment methods, such as ureteroscopicmanipulation with laser lithotripsyor percutaneous nephrolithotomy(PCNL). The passage of stone fragments may take a few days or a week and may cause mild pain. In order to dislodge fragments of the stone and carry them out of the kidney, patients may be subjected to repeated vigorous blows to the kidney while in a head-downward position for a week after the procedure, as well as instructed to drink as much water as is practical.
ESWL is not without risks. The shock waves themselves, as well as cavitationbubbles formed by the agitation of the urine medium can lead to capillary damage, renal parenchymal or subcapsular hemorrhage. This can lead to long-term consequences such as renal failureand hypertension. Overall complication rates of ESWL range from 5-20%.
- Lithotripsy Overview(pdf)
- Lithotripsy (Stones Treatment). Center for Advanced Urology, USA.
- Electromagnetic Technology
- Spark Gap Technology
- How ESL works
Categories: Medical equipment| Urology
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It uses material from the http://en.wikipedia.org/wiki/Lithotriptor Wikipedia article Lithotriptor.