Ancillary US of the Bowel: Endovaginal US, Contrast-enhanced US, and Elastography.

Bowel sonography comprises the study of inflammatory bowel disease (IBD) and other inflammatory and neoplastic bowel conditions associated with gross morphologic change. For the most common application, IBD, it is well established that gray-scale US and color Doppler US imaging (CDI) allow excellent assessment of the status of the bowel wall, blood flow to the bowel and mesentery, and the presence or absence of perienteric inflammatory fat. Although these techniques provide effective and accurate methods to assess the bowel, they are not always comprehensive. Bowel loops residing in the true pelvis may not be accessible from a transabdominal approach, and CDI is not sensitive at increased depths and in patients with obesity. Most important, CDI only shows fast-moving flow in large blood vessels, with a limited ability to show blood flow at the microvascular level. Bowel stiffness is also not included in a standard gray-scale assessment. Three readily available ancillary US techniques can be used to overcome these imaging challenges and to greatly improve detection of pathologic conditions and patient outcomes. These techniques are endovaginal US to visualize pathologic conditions in the deep pelvis, contrast-enhanced US to subjectively and objectively assess blood flow to the capillary level, and two-dimensional shear-wave elastography to determine bowel stiffness as a measure of disease chronicity. The authors provide a detailed description of the application of these techniques with case examples demonstrating the added benefit. ^©RSNA, 2025 Supplemental material is available for this article. See the invited commentary by Barr in this issue.