Ultrasonography of Umbilical Structures

Structures imaged when scanning the foal umbilical area include the external umbilical remnant, umbilical vein, umbilical arteries, urachus, and umbilical hernia if present. The umbilical remnant is located along the ventral midline of the abdomen, a few centimeters from the surface. To locate and recognize the different structures, the easiest way is to start with the cross-sectional view of the external umbilical remnant and move cranially to the xiphoid cartilage. Then, start at the external umbilical remnant again and move caudally to the pelvic rim. If an abnormal structure is suspected, a longitudinal scan should be performed. Optimal equipment to scan the umbilical remnant in the foal is a high-frequency, 10-12 MHz linear probe, although a cursory examination can be performed with a transrectal, 5-7.5 MHz linear probe. Orientation of the probe must be kept constant over time to obtain comparable images.