Erroneous statement regarding 2D ultrasound fetal urinary bladder volume measurement

Abstract

The aim of the current paper is to inform the readers of an erroneous statement on the standard deviation (SD) when estimating the volume of fetal urinary bladder by 2D ultrasound. In the Archives of Gynecology and Obstetrics 2007; 276 (4), page 345–349, the authors Peixoto-Filho F.M. et al. refer to some studies presented by our group versus other studies regarding volume estimation of the fetal urinary bladder, in particular the ellipsoid method pioneered by Stuart Campbell in 1973 and the sum-of-cylinders method from our group. In our studies the volume estimation method was improved in three steps using methodological modifications. The SD was reduced from 17.3–10.9% to 12.9–5.5%, and 8.8–3.5% (bladder volumes 5–40 mL) The reductions were accompanied by P-values of 0.0270 (1 vs. 2) and 0.0543 (2 vs. 3), respectively. When comparing method 3 vs. 1 the P value was 0.0032. The SD reduction using method 3 vs. 2 did not reach statistical significance, however. Using this lack of significance on the 5% significance level, to prove that there were no improvements at all with our methodological modifications of the 2D ultrasound, as done by the authors, is misleading.