How to read an abdominal X-ray
Other platforms explain it with text and video. In VMS you practice it on the patient.
CT has replaced the abdominal X-ray for most problems, but it is still used for bowel obstruction, swallowed objects and checking devices. A clear method makes it quick.
Step by step
Check the details
Confirm the patient, date and whether the patient was lying or upright. [1]
Find small bowel
Small bowel sits in the center and has folds that cross the full width of the loop. [2]
Find large bowel
The colon frames the edges of the abdomen and has folds (haustra) that do not cross the full width. [2]
Measure the loops
Use the 3-6-9 rule in the table below. Dilated small bowel with little gas in the colon suggests obstruction. [2]
Look for free air
Air on both sides of the bowel wall, or under the diaphragm on an upright chest film, means a perforation and needs surgery review. [2]
Look for twists
A large bent loop shaped like a coffee bean rising from the pelvis suggests sigmoid volvulus. [2]
Stones, bones and devices
Check for kidney stones, calcifications, swallowed objects, tubes, stents and the bones of the spine and pelvis. [2]
Common errors
- Missing free air on a lying-down film.
- Mistaking dilated colon for small bowel.
- Relying on a normal X-ray to rule out serious disease.
3-6-9 rule (typical adult upper limits) [2]
| Segment | Upper normal width | Concern if larger |
|---|---|---|
| Small bowel | 3 cm | Obstruction or ileus |
| Colon | 6 cm | Obstruction, volvulus or toxic megacolon |
| Cecum | 9 cm | Risk of perforation |
Practice it in VMS
In VMS you do this on the patient, not on paper: every step goes on the checklist with a score, and in Teach mode Blocky tells you what comes next.
VMS cases that train this skill
Sources
Facts and steps follow AAMC Core Entrustable Professional Activities (Core EPAs); NCCPA PANCE Content Blueprint. VMS is not affiliated with these organizations. Updated: 2026-10-11.