Splenic Trauma & Infarct
- The spleen is the most commonly injured solid organ in blunt abdominal trauma — it's soft, vascular, and parked right under the lower left ribs.
- On contrast CT, hunt for three things: a low-density laceration line, free blood in the belly, and the panic button — a bright blush of leaking contrast (active extravasation).
- A contained blood-filled pouch that follows the artery's brightness on every phase is a pseudoaneurysm; it can blow later, so it changes management even in a stable patient.
- A splenic infarct is the opposite story — a wedge of spleen that stops lighting up because its blood supply got cut, classically pointing toward the hilum.
- Injury severity is described with the AAST grading system, which leans heavily on what the CT shows.
The spleen has a rough job. It's a soft, blood-soaked sponge tucked under the left lower ribs, and its whole personality is "hold lots of blood and ask no questions." That makes it fantastic at filtering your blood and terrible at surviving a handlebar to the flank. When trauma comes through the door and the left ribs are bruised, the spleen is the organ everyone is quietly worried about.
Why the spleen bleeds so eagerly
Think of the spleen as a water balloon filled with red Jell-O and wrapped in a thin paper bag (the capsule). It's almost entirely blood by volume, with very little structural scaffolding holding it together. Tear the bag, and the contents spill into the abdomen. Tear it just on the inside while the capsule holds, and you get a bruise trapped under the wrapper — a contained collection that can rupture hours or even days later when nobody's looking.
This is why the spleen is the most commonly injured solid organ in blunt trauma, and why a "stable" patient with a splenic injury still earns close watching.
What CT actually shows
The workhorse here is contrast-enhanced CT, the same scan you'd order on a polytrauma patient for the whole survey. Normal spleen lights up brightly and evenly once contrast arrives. Injury shows up as the parts that don't behave.
- Laceration: a dark, irregular line cutting into the bright spleen — like a crack running through a lit-up stained-glass window.
- Hematoma: a low-density collection, either inside the spleen (intraparenchymal) or trapped between spleen and capsule (subcapsular), where it flattens the organ's edge like a thumb pressed into dough.
- Hemoperitoneum: free blood pooling in the dependent corners of the abdomen. Fresh-ish clotted blood near the injury can look denser than plain fluid — the so-called sentinel clot, sitting closest to the crime scene.
The two findings that make everyone sit up
Most of the above is "note it and grade it." Two findings change the temperature of the room.
Active extravasation is contrast leaking out of a torn vessel in real time — an ill-defined bright blob, roughly as bright as the aorta, that grows or spreads on later phases because the dye keeps pouring out. That's ongoing arterial bleeding, and it usually means the interventional radiology suite or the operating room, soon.
Pseudoaneurysm is sneakier. It's a contained pouch of blood walled off by injured tissue, fed by a damaged artery. The tell is that it tracks the artery's brightness exactly — bright when the arteries are bright, then fading as the arteries fade — and it stays a tidy, rounded blob rather than spreading. It isn't bleeding right now, but the wall is flimsy and can rupture later.
Active extravasation and a pseudoaneurysm look similar on a single image — both are bright. The difference is behavior across phases: extravasation spreads and grows (free leak), while a pseudoaneurysm stays contained and follows the arterial blood pool like a faithful shadow. Don't call it on one phase alone.
Putting a number on it: AAST grading
Radiologists describe how bad a splenic injury is using the AAST (American Association for the Surgery of Trauma) grading scale, which climbs with bigger lacerations, larger hematomas, and — in the updated version — the presence of vascular injury like extravasation or pseudoaneurysm. The same logic applies to liver and kidney, so it's worth learning the framework once and reusing it across solid organs.
Many splenic injuries are now managed without surgery, and a vascular finding can tip a patient toward angioembolization rather than the OR. So the radiologist who spots a pseudoaneurysm on an otherwise "mild-looking" spleen genuinely changes the plan.
The other story: splenic infarct
Now flip the problem. Trauma is too much disruption; an infarct is not enough blood. When a branch of the splenic artery clots off — from a cardiac embolus, sickle cell disease, endocarditis, a hypercoagulable state, or torsion of a wandering spleen — the tissue it fed simply dies.
On CT, an infarct is a region that fails to enhance: a dark patch in an otherwise bright spleen. Classically it's a wedge, broad at the capsule and pointing toward the hilum, because that's the shape an arterial territory carves out — like a pizza slice with the tip aimed at the center where the vessels enter.
A wedge of non-enhancing spleen pointing toward the hilum, in a patient with no trauma history but an irregular heartbeat or sickle cell disease, is the classic infarct picture. Over time the wedge can shrink and scar, leaving a notched, smaller spleen.
The one thing to carry out the door
For trauma: on contrast CT, find the laceration and the free blood, but reserve your adrenaline for the bright blush. Then decide whether it spreads (active bleeding) or stays put and follows the arteries (pseudoaneurysm) — that distinction, plus the FAST exam (Focused Assessment with Sonography for Trauma) at the bedside, drives what happens next. For infarct: think of a non-enhancing wedge pointing home toward the hilum, and ask where the clot came from.