Small intestinal obstruction from foreign material, masses, and intussusceptions is a common cause of vomiting.1 Recognizing radiographic and ultrasonographic signs is necessary for correct diagnosis.2,3
A backup of ingesta proximal to the obstruction site can cause bowel distention (See Figures 2–6). Complete and some chronic partial obstructions can cause significant bowel dilation, and often the colon is empty. Depending on the obstruction site, the segment of bowel distention may be short or long. Compared with the small intestine, the colon is typically larger in diameter and contains fecal material. Differentiating small intestine from colon is crucial for accurate diagnosis: mistaking colon for small intestine can lead to incorrect diagnosis of small bowel obstruction, while mistaking distended small intestine for colon can lead to a missed diagnosis of small intestinal obstruction (Figure 6). Both lateral and ventrodorsal views are essential for accurate assessment, although both may not be presented in this collection.
Ultrasonography is often used to assess vomiting and can reliably diagnose small bowel obstruction.4-6 Compared with radiography, ultrasonography can identify underlying causes more frequently.4-6 Challenges include the presence of bowel gas (hiding foreign material), ultrasonographer experience, relatively small field of vision, and differentiation of small intestine from colon.
Related Article: Feline Intestinal Foreign Bodies
Overlap exists between normal (See Figure 1) and obstructive bowel diameter.4 Proximal obstructions can have a short segment of duodenal distention, and distal obstructions can have longer segments of small intestinal distention. Recognizing mixed populations of normal and distended bowel is common in small intestinal obstruction. The small intestine should contain only homogeneous soft tissue opacity (fluid, liquid ingesta) and/or gas. Heterogeneous material (often feces-like) is a sign of potential obstruction from foreign material or inhibition of passage of normal ingesta.
1. Normal Small Intestinal Diameter, Contents, & Distribution