Which diagnostic modality is most useful to rule out small intestinal volvulus, intussusception, or abdominal hernias in a foal with colic?

• A. Ultrasound
• B. Radiographs
• C. CT scan
• D. Endoscopy

Answer: (A)

Ultrasound is the most useful tool because it lets you rapidly see the entire abdomen in a live foal and assess the small-intestinal loops, their walls, contents, and surrounding structures without invasive procedures. With ultrasound you can gauge loop size, wall thickness, and motility, and you can look for free intraperitoneal fluid or signs of compromised blood flow, all of which help distinguish specific problems.

For intussusception, ultrasound often shows a characteristic concentric “target” or donut appearance in cross-section or a telescoped, layered bowel—clear signs that a segment has invaginated into another. For a small intestinal volvulus, you may detect a twisted arrangement of the mesentery and vessels, sometimes described as a whirl or abnormal orientation of the loops, along with dilated, nonfunctional loops. Abdominal hernias appear as a defect in the abdominal wall with loops of bowel protruding through the opening, sometimes with a defined hernial sac and surrounding tissue.

Other imaging methods have limitations in foals: radiographs can be inconclusive because gas distends the intestines and obscure details; CT provides excellent detail but is often unavailable in field settings and requires more resources and anesthesia; endoscopy is focused on the mucosal surfaces of the upper GI tract and isn’t practical for evaluating abdominal organs. Ultrasound thus offers the quickest, most informative, noninvasive way to rule out these causes in a colicky foal.