What is the role of extracorporeal shockwave lithotripsy (ESWL) in the treatment of nephrolithiasis?

Updated: Jun 21, 2018
  • Author: Chirag N Dave, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Answer

ESWL, the least invasive of the surgical methods of stone removal, utilizes high-energy sound waves focused on the stone to shatter it into passable fragments. It is especially suitable for stones that are smaller than 2 cm and lodged in the upper or middle calyx. It is contraindicated in pregnancy, patients with untreatable bleeding disorders, tightly impacted stones, or in cases of ureteral obstruction distal to the stone. In addition, the effectiveness is limited for very hard stones (which tend to be dense on CT scan), cystine stones, and in very large patients.

The patient, under varying degrees of anesthesia (depending on the type of lithotriptor used), is placed on a table or in a gantry that is then brought into contact with the shock head. The deeper the anesthesia (general endotracheal), the better the results. In addition, evidence is mounting that slower shockwave delivery (60-80 per min) improves the results. Likewise, starting SWL on a lower energy setting with stepwise power (and SWL sequence) ramping has also been advocated in order to achieve vasoconstriction during treatment, which prevents renal injury as well as increase SFR (stone free rates). These are based on findings in some animal studies and a prospective randomized study, but did not find clear evidence of difference in complications or fragmentation size based on use of ramping. [72, 73]

New lithotriptors that have two shock heads, which deliver a synchronous or asynchronous pair of shocks (possibly increasing efficacy), have attracted great interest. The shock head delivers shockwaves developed from an electrohydraulic, electromagnetic, or piezoelectric source. The shockwaves are focused on the calculus, and the energy released as the shockwave impacts the stone produces fragmentation. The resulting small fragments pass in the urine.

ESWL is limited somewhat by the size and location of the calculus. A stone larger than 1.5 cm in diameter or one located in the lower section of the kidney is treated less successfully. Fragmentation still occurs, but the large volume of fragments or their location in a dependent section of the kidney precludes complete passage. In addition, results may not be optimal in large patients, especially if the skin-to-stone distance exceeds 10 cm. [74]


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