Discussed August 19th, 2006.

Several posters advocated ureteroscopy over the more traditional SWL as first-line therapy in pediatric patients. With the technological improvements in flexible and semi-rigid ureteroscopes, this application will continue.

Some experts cautioned against liberal manipulation of the lower urinary tract in boys as this may contribute to urethral stricture; a ureteral access sheath should be used in these cases. While first-line URS for pediatric patients represents is being practiced at several centers, there were several compelling reports confirming the efficacy of SWL. Nadler’s group from Chicago looked at 48 pediatric patients who underwent SWL with an HM3 or LithoTron. Overall stone clearance rate was 83% at 3 months, with 97% clearance for solitary stones vs. 61% for multiple stones and 100% for ureteral stones.

Chaussy’s group from Germany reported on their experience over the past 18 years with 96 children and 147 procedures (VP11-7). With a 28% retreatment rate, 96% of children with ureteral stones and 90% with renal stones (without any renal abnormality) were rendered stone-free. In children with renal or congenital abnormalities, stone free rate dropped to 45%. Based on these two large series, it appears that SWL should still be considered as first line treatment for the majority of pediatric stones. However, children with multiple stones or renal or congenital abnormalities may benefit from primary ureteroscopy.

Several posters looked at factors contributing to SWL failure, particularly skin to stone distance (SSD) and stone density as measured by Hounsfield Units (HU). Goren et al from Turkey found that a SSD of ³12 cm (measured at a 45º angle from the center of the stone on a CT scan) was associated with high rates of SWL failure (VP11-12). However, Erturk’s group from Rochester, NY found no effect of SSD on SWL failure rate (VP11-15). They did, however, note a significant effect of HU<660 on univariate but not multivariate analysis. Honey’s group from Toronto, Canada retrospectively evaluated SWL failure in 105 patients (VP11-19). Only stone density held up on multivariate analysis as predictive of SWL success, with stones >1000HU 5.5 times more likely to fail SWL. Finally, Nakada’s group from Wisconsin looked at the best way to determine maximum HUs on a CT scan (VP11-21). They compared the traditional view using abdominal windows with bone windows. 65% of the time, the highest HUs for either view was found in the image with the largest stone diameter. Further, Bone windows determined the maximum HU 85% of the time compared to 68% for abdominal windows. Thus, examining noncontrast CT scans using bone windows will significantly improve one’s ability to determine stone density by maximum HU, and therefore to predict stone fragility and appropriateness for SWL, laser lithotripsy, or ultrasonic lithotripsy. This may be particularly useful in planning therapy for lower pole stones, or renal pelvis stones 1-2 cm, which could be amenable to several treatment modalities.

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