Extracorporeal shock wave lithotripsy has been the treatment of choice for symptomatic upper urinary tract stones in adults since 1980s, when the first-generation machines, featuring spark-gap electrodes, were introduced. Initially reported in 1986 large series of ESWL in children demonstrated complications, safety and stone-free rates similar to those in adults.[23
] To decrease the pain experienced by patient, which is a function of the size of the focal point and the amount of energy focused at that point as well as the surface area over which the shock wave enters, new second- and third-generation machines with electromagnetic generators were introduced. Therefore, intravenous sedation instead of general anesthesia can now be used in older pediatric patients.[24
] Introduction of newer compact portable ESWL machines allows pediatric urologists to perform outpatient treatment conveniently at their own institution, with the added safety of dedicated pediatric anesthesia. Positioning of the child is extremely simplified and additional endoscopic procedures (ureteral stent placement or removal) can be performed simultaneously since these machines incorporate a universal urological table.[26
] Radiation exposure during ESWL is minimal and comparable with that of routine diagnostic uroradiological examinations.[28
Given its minimally invasive features, ESWL has become a primary mode of treatment for pediatric patients with reno-ureteral stones.[29
] Further studies determining a definitive size cutoff for upper tract stone burden is necessary to recommend the most effective first-line therapy for larger stones (above 1-1.5 cm). Stone-free rates have been reported from 59% to 91%[24
] although some patients will require more than one treatment session for stone clearance. Current success rates are difficult to interpret from existing literature due to discrepancies among studies regarding the definition of stone-free status, type of lithotriptor, stones locations and sizes, and number of shocks administered. In most pediatric series, the treatment of proximal ureteral stones has achieved similar success rates to renal stones.
Treatment of mid to distal ureteral calculi has historically been avoided in children due to difficulties with localization over the sacroiliac joint and concern regarding possible injury to the developing reproductive system. Thus far there is no evidence that ESWL for distal and mid-ureteral stones in adults exerts any detrimental effect on female and male fertility.[32
] In an in vitro
animal study, rat ovaries were subjected to shock waves. The results showed no differences between experimental and control groups in the rate of subsequent pregnancies, fetal numbers, spontaneous abortions, and malformations.[33
] However, this issue has yet to be clarified in the long-term studies in children. For the mid-ureter, the density of bony pelvis is less in children and this probably results in a higher success rate than in adults.
One of the first reports of ESWL monotherapy for ureteral stones in 38 pre-pubertal children demonstrated success rates of 81.5% after one session with an overall stone-free rate of 97.3%.[34
] Stones were located in the upper ureter in 17 cases, mid-ureter in 2, and lower ureter in 19. The stone-free rate following one ESWL session was 100% for ureteral calculi smaller than 10 mm regardless of the location and 67% for stones larger than 10 mm. The same group later reported overall success rate of 98.3% in 59 patients with ureteral stones treated with ESWL over a 22-year-period. The three-month stone-free rate did not depend on either stone location or size.[30
] The largest to-date published series of ESWL of ureteric stones in children reported results among 192 patients.[24
] The overall stone-free rate was 91% with a retreatment rate of 49%. That rate was 94% for all proximal and mid-ureteral stones and 91% distal ureteral stones.
ESWL for ureteral stones is highly satisfactory. The high success rate observed throughout the ureter can possible be explained by the fact that the pediatric ureter is more short, elastic, and distensible. Such structure allows for easier transmission of stone fragments and prevents ureteral impaction. Ureteral stenting before ESWL remains a controversial issue, and often depends on both the stone size and patient′s anatomy. It was shown that pediatric ureter is at least as efficient as the adult for transporting stone fragments after ESWL.[35
] The incidence of Steinstrasse following ESWL in children without ureteral stents has shown to be very low (significantly lower than for adults).[2
] As a result, preoperative stenting is generally reserved for children with solitary kidney, severely obstructing stones, or abnormal anatomy.