Fetal Echogenic Bowel: What Is Real Echogenicity? A Quantitative Method Based on Histogram Analysis of the Grayscale

The aim of this study was to use computerized analysis of the grayscale spectrum (histogram) to provide an objective assessment of the echogenicity of the fetal bowel. Moreover, we investigated the role of histogram analysis in the prenatal prediction of postnatal outcomes in fetuses with echogenic bowel (fetal echogenic bowel [FEB]).

This is a single-center retrospective study including all fetuses with a diagnosis of echogenic bowel (FEB) in the mid-second trimester between 2015 and 2021. Ultrasound images were analyzed using ImageJ software. The mean of the grayscale histograms of the bowel, liver, and iliac/femur bone was obtained for each patient, and the ratio between these structures was used to overcome gain variations. We compared these values with those of a matched control group of singleton uncomplicated pregnancies and with a group of patients referred for FEB, where the FEB was not confirmed by the expert operator (FEB false-positive).

There was a statistically significant difference between bowel/liver and bowel/bone histogram ratios between the FEB group and the control groups (p < 0.05). Mean ratio cutoffs were provided for the diagnosis of FEB. Among the patients with confirmed FEB, both ratios were not able to discriminate the cases with adverse outcomes. In contrast, the presence of dilated bowel or other markers was associated with an adverse outcome.

Histogram analysis may refine the diagnosis of FEB and reduce the number of false-positive diagnoses. For the prediction of the fetal outcome, the presence of additional features is clinically more significant than the degree of bowel echogenicity.