RESUMO
PURPOSE: Prospective evaluation of the accuracy of three-dimensional ultrasound (3DUS) to assess the renal parenchymal volume. MATERIALS AND METHODS: CT, MRI, 2DUS and 3DUS were used to measure the renal volume in 40 patients (range: neonate to 17 years; mean age: 8.95 years). The 3DUS was determined with a Voluson 730 (Kretztechnik, GE) or an external 3D-system (EchoTech, GE) using electromagnetic positioning sensors attached to conventional 2DUS-equipment. The 2DUS volume was calculated with the ellipsoid equation and the 3DUS volume computed with the system integrated software. For CT and MRI, planimetric analysis was used to determine the renal parenchymal volume, whereby the dilated collecting system of a hydronephrosis was subtracted to obtain the real renal parenchymal volume. The results of 2DUS and 3DUS were compared to the results of CT and MRI, and inter- and intraobserver variabilities were calculated. RESULTS: In 74 of 77 kidneys, the 3DUS study was of diagnostic quality. The accuracy of the 3DUS volumes compared well to the CT and MRI volumes with a mean difference of -1.8 +/- 4.6 % versus a mean difference of -2.4 +/- 15.4 % for 2DUS. In normal kidneys, the accuracy was -2.6 +/- 4.4 % for 3DUS and -3.8 +/- 14.7 % for 2DUS. In hydronephrosis, the accuracy was +4.0 +/- 5.9 % and +9.6 +/- 21.3 %, respectively, indicating that 3DUS is more accurate than 2DUS, particularly in kidneys with a dilated collecting system. Inter- and intraobserver variabilities were +/- 7.3 % and +/- 5.3 %. CONCLUSION: For assessing the renal parenchymal volume in children, 3DUS is feasible and comparable to CT and MRI.
