Radiological Anatomy: Small Intestine

OVERVIEW

This page is dedicated to covering how the small intestine will appear across different radiological studies.

ABDOMINAL X-RAY

An abdominal X-ray is a very routinely ordered study, and a core component of reading this study is to evaluate the appearance of the small intestine.

Appearance of small bowel on an abdominal X-ray. Notice that valvulae (folds of the small intestine marked by red arrows) should extend across the whole length of the lumen of the small bowel. This is NOT a unremarkable study, the small bowel is diffusely dilated, which makes it easier to see (source)
Appearance of small bowel on an abdominal X-ray. Notice that valvulae (folds of the small intestine marked by red arrows) should extend across the whole length of the lumen of the small bowel. This is NOT a unremarkable study, the small bowel is diffusely dilated, which makes it easier to see (source)

Characteristics of the small bowel on a KUB: the below features can help identify the small bowel on a KUB.

  • Central location: generally these bowel loops will be located more in the central region of the abdomen (compared to the large intestine)
  • Presence of air: there are generally 2-3 locations that are air filled in a “normal” small bowel.
  • Air/fluid levels: three or less fluid levels are within the range of normal
  • Diameter: the normal diameter of the small bower is < 2.5 cm (~ 1 inch). When maximally dilated it is about 5.0 cm.
  • Valvulae: these are folds of the small bowel that span the entire lumen, and can appear clearly as “white lines” on the film (intestinal markings).

 

Page Updated: 10.07.2016