Dilatation (Small Bowel)

The most important abnormal feature is dilatation.

The small bowel lies in the central area of the abdomen (Fig 1). It is recognised by valvulae conniventes which are folds that form complete bands across the lumen. Their width should not exceed 2.5cm.

Dilatation can be widespread in small bowel obstruction (SBO) or more localised e.g. the sentinel loops of pancreatitis (Fig 2). Complete SBO will, after a while, lead to the large bowel collapsing and being devoid of air.

Fig 1: Abdominal x-ray of the small bowel Fig 2: Abdominal x-ray of a focal dilated small bowel in pancreatitis

What can cause dilation in the small bowel?

The causes are:

  • Adhesions (75%)
  • Strangulated hernia (10%)
  • Appendix abscess
  • Gallstone ileus
  • Crohn’s disease
  • Tumour
  • Intussusception
  • Volvulus

Learning bite

In small bowel obstruction always consider adhesions and strangulated herniae as the most likely causes.