**3.2 Small and large bowel**

In patients with abdominal trauma, the bowel wall can be examined. However, the focused examination would be more effective than screening the entire bowel at the bedside. A high-frequency linear array probe is used to scan the bowel. It can even distinguish between the bowel wall layers. The small bowel can be differentiated from the large bowel by the size, location, and absence of haustrae. When scanning the large bowel, gentle pressure is applied with the transducer to displace bowel gas and small bowel loops from the view.

Studies have shown POCUS to be superior to plain radiography in identifying bowel obstruction. Features suggestive of obstruction include dilatation of bowel with fluid content proximal to the obstruction and collapsed distal bowel (**Figure 9**). In the case of ileus, there would be no transition point from dilated to collapsed bowel. As time progresses, the bowel wall thickens, and peritoneal

#### **Figure 8.**

*Free air of pneumoperitoneum overlying liver surface with enhanced peritoneal stripe (black arrows) and reverberation artifacts (white arrows) [19].*

**Figure 9.** *Dilated bowel loops in intestinal obstruction as seen on USG [20].*

free fluid develops. Peristaltic activity in the bowel can be seen as a to-and-fro movement of spot echoes within the bowel loop. Bowel strangulation can also be identified with POCUS – dilated aperistaltic proximal bowel loop with peristalsis seen in further proximal bowel, asymmetric bowel wall thickening with an accumulation of intraperitoneal fluid.
