Ultrasonography of the Small Intestine in Small Animals

Examination techniques

Ideally, the patient should be fasted overnight to reduce the interference with gastric contents and intraluminal gas. However, non-fasted dogs may showadequateimagequality. Theintra-luminalgas causes imaging artifacts, such as reverberation, comet tail and acoustic shadowing. Sedation is not usually necessary, but when needed, xylazine should be avoided because it causes gastric stasis leading to massive gaseous distension (1).

The animal is typically placed in dorsal recumbency, although the position may depend on the patient’s restlessness, discomfort, or on the operator’s preferences. The examination with the patient standing, or via a hole in the supporting table, the recumbent side is useful. This makes use of the intraluminal fluid gravitating to the dependent wall of the stomach or intestinal tract where it serves as an acoustic window (2).

Five MHz, 7.5 MHz or higher frequency transducers are used, with higher frequency transducers offering the best resolution of bowel wall layers (1,2). Transducers with small footprint are useful to evaluate the proximal duodenum when the probe must be placed below the rib cage or between ribs (2). [...]

Key Points

• Ultrasound examination of the small intestine has become routine in investigation of the intestinal diseases

• The principal limitation of intestinal tract ultrasound is the presence of luminal gas

• Radiographs should precede the ultrasound examination to evaluate the amount, location and pattern of intestinal gas

• Ultrasound examination can provide information of bowel wall thickness, layering of the wall, peristalsis, and luminal contents