The injury CT misses most: look for a bowel wall defect, extraluminal gas, a mesenteric haematoma or active mesenteric bleeding, and unexplained free fluid — each of which, without a solid organ injury to explain it, must be said out loud.
Orient first
- Bowel and mesenteric injuries are uncommon but are missed at a much higher rate than solid organ injuries, and delay in diagnosing them causes peritonitis.
- A seatbelt mark on the abdominal wall, a Chance fracture or a lap-belt mechanism raises the prior sharply.
- Free fluid in a man with no solid organ injury is unexplained until the bowel and mesentery have been examined; in a woman of reproductive age a small pelvic volume can be physiological.
Acquire the study
- Trauma CT with an ARTERIAL phase (or a split-bolus single acquisition) and a PORTAL VENOUS phase; add a DELAYED phase (about 5–10 min) whenever there is solid organ injury or free fluid of uncertain source — it separates active bleeding from a contained vascular injury and shows urine leaks.
- Thin slices with CORONAL and SAGITTAL reformats; read the arterial and portal venous phases side by side.
- Re-window every study to a LUNG or wide window over the abdomen to find extraluminal gas.
The manoeuvre
- Lung window over the whole abdomen: gas outside bowel — anterior to the liver, in the mesentery, in the retroperitoneum.
- Each bowel loop on portal venous phase: focal wall discontinuity; wall thickening; abnormal wall enhancement (hypoenhancement = ischaemia; hyperenhancement = shock bowel if diffuse).
- The mesentery: haematoma (triangular high-attenuation fluid between leaves), stranding, and beading or abrupt termination of mesenteric vessels.
- Active mesenteric extravasation across the arterial, portal venous and delayed phases.
- Free fluid: location and attenuation; interloop fluid in triangular pockets between loops is more worrying than fluid in the pelvis alone.
- Abdominal wall: seatbelt haematoma, and traumatic abdominal wall hernia.
What confirms it
- Bowel wall discontinuity or extraluminal gas not explained by another cause; active mesenteric extravasation; mesenteric haematoma with adjacent bowel wall abnormality.
What licenses you to exclude it
- A normal CT reduces but does not exclude bowel injury; unexplained free fluid, a seatbelt sign or evolving clinical signs warrant observation and a repeat CT or laparoscopy.
The classic misread
- Calling extraluminal gas from a pneumothorax/pneumomediastinum tracking down, or from a urinary catheter or peritoneal lavage, a bowel perforation — trace its source.
- Calling diffuse bowel wall hyperenhancement with a flat IVC and small aorta (shock bowel / hypoperfusion complex) a bowel injury.
- Reporting "small volume free fluid" without saying whether a solid organ injury explains it.