Investigation

The investigations of worth in suspected bowel obstruction include:

• routine bloods for any disturbances caused by the obstruction
• abdominal radiographs:
  • supine - may show which piece of gut is obstructed
  • erect - may show fluid levels

A radiological diameter of the caecum of 12 cm or more implies that the ileocaecal valve is still patent, i.e. the increased pressure in the large intestine has not decompensated into the small intestine. This is a poor sign, and implies that there is imminent danger of rupture.

In large bowel obstruction of a less acute onset, a barium enema may help to demonstrate the nature of the obstructing lesion.

Note that in a small percentage of intestinal obstructions there is no abnormality seen on plain abdominal X-ray. This occurs when the bowel is completely distended with fluid in a closed loop and without the fluid levels produced by coexistent gas.

Computed tomography scanning is now viewed as usually the most appropriate and accurate diagnostic imaging modality for most suspected bowel obstructions. It is practical to obtain, accurate for diagnosis, and provides substantial information to help determine the cause of obstruction and identify complications. (2)

MRI scanning is an alternative cross-sectional modality that can exceed the accuracy of CT, but practical considerations significantly limit its use. (2)

Reference

1. Association of Surgeons of Great Britain and Ireland; Royal College of Surgeons of England. Commissioning guide: emergency general surgery (acute abdominal pain). April 2014 [internet publication].
2. Nelms D. Imaging Modalities for Evaluation of Intestinal Obstruction. Clin Colon Rectal Surg. 2021 Jun 2;34(4):205–218.