Pelvic Trauma & Bleeding
- The bony pelvis is a ring, and a ring almost never breaks in just one place — see one fracture, go hunting for the second.
- The real danger usually isn't the bone; it's the vascular plumbing torn alongside it. Pelvic bleeding can quietly fill the retroperitoneum and exsanguinate someone.
- On contrast-enhanced CT, the finding that changes everything is a blush of contrast outside the vessels — active arterial extravasation that says "this patient needs the angio suite, now."
- Arterial bleeds go to interventional radiology for embolization; venous and bony bleeds usually respond to pelvic binders and packing. Telling them apart is the whole game.
A pelvic fracture is one of those injuries where the broken bone is almost the boring part. The pelvis is basically a bony donut wrapped around a tangle of large arteries and veins, and when the donut snaps, those vessels can tear. People don't usually die from the fracture — they die from the bleeding hiding behind it. So our job on imaging is less "name the fracture" and more "find the leak before it finds the patient."
The ring rule (and why it matters)
Think of the bony pelvis as a closed ring of stiff licorice. Try to snap a closed ring in a single spot — you can't, really. It bends and then gives way somewhere else too. So when a pelvic or acetabular fracture breaks the ring in one place, there's almost always a second break or a sprung joint elsewhere (often the sacroiliac joint or pubic symphysis out front).
This isn't trivia. A pelvis that's broken in two places can spring open like a book, and a wide-open pelvis means a bigger empty space for blood to pour into and a lot more torn tissue doing the pouring.
One pelvic ring fracture is your cue to deliberately search for the second injury. A "single" ring break is usually a missed one.
What's actually bleeding
Most life-threatening pelvic hemorrhage comes from one of three sources, and they don't behave the same way:
| Source | Behavior | Usual treatment |
|---|---|---|
| Arterial | Fast, high-pressure, won't tamponade on its own | Angiography + embolization |
| Venous (presacral plexus) | Slower, lower-pressure, often tamponades with pressure | Pelvic binder, packing, resuscitation |
| Bony / fracture surfaces | Oozing from raw bone ends | Reduction and stabilization |
Venous and bony bleeding is the common stuff, and a lot of it stops once you squeeze the pelvis back together — that's the entire logic behind slapping on a pelvic binder. Arterial bleeding is the diva: high pressure, no interest in tamponading, and the thing that lands a patient in the interventional radiology suite for embolization.
The finding that changes the plan: the contrast blush
Here's where contrast-enhanced CT earns its keep. We inject iodinated contrast, which lights up the inside of vessels bright white. If a vessel is torn and actively leaking, that bright contrast spills out of the lumen and pools in the tissues — a focal, irregular blob of high density sitting where it has no business being. Radiologists call it active extravasation or, more affectionately, a contrast blush. It's the imaging equivalent of finding the puddle under the leaking pipe.
The tell that it's arterial (and therefore an embolization candidate) is timing: a true arterial blush appears on the early arterial-phase images and tends to grow or spread on later (venous/delayed) phases, because it's being actively pumped out under pressure. This is exactly why pelvic trauma protocols often run more than one phase — a single snapshot can't show you whether the puddle is growing.
A contrast blush in an unstable trauma patient is a "stop scrolling and pick up the phone" finding. Active pelvic arterial bleeding can exsanguinate fast, and the fix — embolization or surgery — is time-critical. Don't bury it at the bottom of the report.
Hematoma vs. active leak — don't confuse the puddle with the stain
A big retroperitoneal hematoma — a clot of pooled blood — is denser than normal tissue but not as bright as fresh contrast, and it doesn't change between phases because it's just sitting there. The active blush is brighter and grows. Mixing these up is the classic rookie error.
A bladder full of contrast-laced urine (excreted contrast on delayed images) can mimic extravasation, and so can a contrast-filled bladder rupture. Check where the density is, whether it connects to the bladder, and whether it tracks like urine or like blood. Anatomy and phase timing usually sort it out.
How this fits the bigger trauma picture
Pelvic bleeding rarely travels alone — it's part of the whole-body survey in blunt abdominal trauma, and the bedside FAST and eFAST ultrasound may have already flagged free fluid before the patient ever reached the CT scanner. The CT then answers the questions ultrasound can't: which vessel, how fast, and does this go to IR or to the OR.
If you remember one thing: with the pelvis, don't fall in love with the fracture. Find the bleed, decide whether it's arterial, and get it to the right room. The bone will still be broken tomorrow — the patient might not be if you miss the blush today.