abdominal x-ray
Meaning of abdominal x-ray: A quick plain film of the belly that is read mainly from the pattern of gas rather than from the organs themselves.
Definition of abdominal x-ray
An abdominal x-ray is a plain radiograph of the belly, made by passing a brief burst of radiation through the body onto a detector. Dense structures such as bone and some stones appear white, gas appears black, and the soft organs blur together in shades of gray. It is fast, widely available and delivers a modest radiation dose.
What can it show?
| Finding | What it suggests |
|---|---|
| Dilated bowel loops with fluid levels | Obstruction of the bowel |
| Gas outside the bowel, under the diaphragm | Perforation of a hollow organ |
| Dense object in an unexpected place | A swallowed foreign body |
| Tube or line tip in the wrong position | Misplacement needing correction |
| Calcified density along the urinary tract | A stone, though many are not visible this way |
| Abnormal gas within the bowel wall | Severe bowel injury |
What does it miss?
A great deal. Appendicitis, most gallstones, early loss of blood supply to the bowel, internal bleeding, tumors and abscesses are all invisible or nearly so, because soft tissues absorb radiation too similarly to be told apart. A normal film therefore excludes very little, and this is the single most important thing to understand about the test. Computed tomography and abdominal ultrasound have replaced it for most diagnostic questions, and the plain film survives mainly for quick answers about obstruction, foreign bodies and the position of tubes.
Why do the views matter?
A film taken lying down shows the distribution of gas within the bowel. Free gas outside the bowel, however, floats upward, so it is only reliably seen on a film taken with the patient upright or lying on one side, where it collects against the diaphragm or the flank. Asking for the wrong view is a recognized way to miss a perforation entirely.
What about the radiation?
The dose to the abdomen is higher than for a chest film, though still small, and it is a form of ionizing energy, meaning it carries enough energy to damage DNA. Requests are weighed against the value of the answer, and pregnancy is asked about before imaging this region. Where the same question can be answered with ultrasound, which uses sound rather than radiation, that is generally preferred in pregnancy and in children.
What are the standard views?
A single film with the patient lying on the back is the usual starting point, sometimes called a KUB because it covers the kidneys, ureters and bladder. Additional upright or side-lying films are added when free gas is the question.
Also known as
Used in a sentence
The abdominal x-ray showed dilated small bowel loops with multiple air-fluid levels.
Good to know
A normal abdominal x-ray rules out very little, and free gas from a perforation is reliably seen only on a film taken upright or with the patient lying on one side.