Reproducibility of fetal renal pelvis volume assessed by three-dimensional ultrasonography with two different measurement techniques.

Purpose: To evaluate reproducibility of fetal renal pelvis volume as assessed by the Virtual Organ Computer Aided AnaLysis (VOCAL) imaging program and by Automatic Volume Calculation (SonoAVC). In addition, the intra- and interobserver reliability of fetal renal pelvis volume measurements with SonoAVC were established.

Methods: In this study, the fetal renal pelvis volume was measured using 3D ultrasonography in 76 kidneys of 66 fetuses with renal pelvis dilatation in the second or third trimester of pregnancy. After volume acquisition by one observer, the reproducibility of volume calculation was assessed using VOCAL imaging program and SonoAVC by two observers. Intra- and interobserver reproducibility was evaluated by calculating intraclass correlation coefficients (ICC), coefficient of variation (CV) and repeatability coefficient (r). Bland-Altman plots were generated to explore agreement.

Results: A high degree of reproducibility was observed between VOCAL and SonoAVC, ICC of 0.989; 95% CI 0.983-0.993, respectively. Intraobserver reproducibility of volume measurements performed by SonoAVC demonstrated a high degree of reliability with ICC of 0.995 (95% CI 0.993-0.997), CV 6.05% and r of 0.75. The interobserver reproducibility with ICC of 0.995 (95% CI 0.992-0.997), CV 10.14% and r 1.21 was also indicative of good reliability.

Conclusion: Volume measurements of fetal renal pelvis performed by SonoAVC renders reproducible measurements in comparison with the VOCAL imaging program. There is no significant difference between VOCAL imaging program and SonoAVC. The intra- and interobserver reliability of the fetal renal pelvis measurements made by SonoAVC were considered to be very good. SonoAVC, however, needs post processing in the majority of cases but is less time consuming than VOCAL.