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Background: In modern pediatric urology, shock wave lithotripsy (SWL) is an option for the treatment of most upper urinary tract stones. One of the factors determining the success of the procedure is stone radiodensity, as measured in the units of Hounsfield scale (HU). Compared to the adult population, little is known about the impact of stone radiodensity on SWL outcomes in children.
Methods: 46 patients (aged 6 months to 17 years) underwent SWL of upper urinary tract calculi from January 2007 to December 2012. All patients underwent an evaluation of stone radiodensity using computed tomography (CT) preoperatively. Outcomes of SWL were evaluated using ultrasound (US) on an average of 50 days after the procedure. SWL results were registered for each observation as: stone-free, complete fragmentation, incomplete fragmentation or lack of change.
Results: Thirty three children (71%) were stone-free or had complete fragmentation following SWL. Stone radiodensity was statistically significant between stone free or complete fragmentation (median 900 HU, Range: 200-1530), and incomplete fragmentation or lack of change (median 1275 HU, Range: 715-1445) groups (p<0.1). There was a significant difference between these two groups according to stone volume as well: 0.663 cm³ and 2.14 cm³ respectively (p<0.1). If divided into groups according to stone radiodensity, SWL for stones <900 HU had a 94.4% stone-free or complete fragmentation rate, compared to 57.1% for patients with the density of the stone> 900 HU (p<0.05). But for our patient sample we found no statistically significant difference in outcome for patients with stones >1 cm³ and < 1 cm³ in volume. For stones >1 cm³ in volume SWL had a 30.7% success rate, compared to 87.9% for patients with stones < 1 cm³ (p>0.05).
Conclusions: Our preliminary results confirm that stone radiodensity and stone volume are important predictors of SWL outcomes in children as in adults. Potentially, these results will allow selection of the most appropriate strategy for surgical treatment of different types of stones in pediatric population.