Visualization of urinary stones by 3-D ultrasound with surface rendering.

The purpose of this study was to evaluate the diagnostic value of 3-D ultrasound with surface rendering in stones located in different parts of the urinary tract. A total of 55 patients with urinary stones were examined by transabdominal 3-D ultrasound (US) with surface rendering of the stone. In calculi of the prevesical ureter, bladder and prostatic urethra, transrectal 3-D endosonography was performed as well. The radiographic shape and the chemical analysis of the stone were correlated to the sonographic findings. The localization of the stone was: renal 23, ureteral 26, vesical 5 and urethral 1. All stones could be identified by 3-D US. Surface rendering produced useful results in stones > 2 cm with a 3.5-MHz transabdominal scanning probe, and in all stones that were accessible with a 7.5-MHz transrectal scanning probe. In stones < 1 cm, endoUS with surface rendering provides more information on the structure of the stone than plain radiography, but there is no correlation between surface and chemical analysis.