Extracorporeal Shockwave Lithotripsy in Pediatrics

Abstract

Since its introduction in 1980, extracorporeal shockwave lithotripsy (SWL) has become the first therapeutic option in most cases of upper-tract urolithiasis, and the technique has been used for pediatric renal stones since the first report of success in 1986. Lithotripter effectiveness depends on the power expressed at the focal point. Closely correlated with the power is the pain produced by the shockwaves. By reducing the dimensions of the focus, it becomes possible to treat the patient without anesthesia or analgesia but at the cost of a higher re-treatment rate. Older children often tolerate SWL under intravenous sedation, and minimal anesthesia is applicable for most patients treated with second- and third-generation lithotripters. Ureteral stenting before SWL has been controversial. Current data suggest that preoperative stent placement should be reserved for a few specific cases. Stone-free rates in pediatric SWL exceed 70% at 3 months, with the rate reaching 100% in many series. Even the low-birth-weight infant can be treated with a stone-free as high as 100%. How can one explain the good results? Possible explanations include the lesser length of the child's ureter, which partially compensates for the narrower lumen. Moreover, the pediatric ureter is more elastic and distensible, which facilitates passage of stone fragments and prevents impaction. Another factor is shockwave reproduction in the body: there is a 10% to 20% damping of shockwave energy as it travels through 6 cm of body tissue, so the small body volume of the child allows the shockwaves to be transmitted with little loss of energy. There are several concerns regarding the possible detrimental effect of shockwaves on growing kidneys. Various renal injures have been documented with all type of lithotripters. On the other hand, several studies have not shown adverse effects. In general, SWL is considered to be the method of choice for managing the majority of urinary stones in children of all ages. Re-treatments improve the stone-free rate, often raising it to 100%. Among the predictors of success, stone size seems to be the most important. In the absence of guidelines, selecting the appropriate treatment modality for each child requires planning and depends on instrument availability and local expertise.