Splenic Lesions
- The spleen is the organ everyone forgets until something shows up in it — and most of what shows up is boringly benign.
- Cysts and hemangiomas are the common, sleep-easy findings; the spleen's job (filtering blood) makes it a frequent home for infarcts and metastases too.
- A single splenic lesion is usually benign; multiple lesions in a sick patient shift your worry toward infection or malignancy.
- The spleen's normal enhancement on contrast CT is famously weird and stripey early on — don't call that a lesion.
- An enlarged, lacerated, or "shattered" spleen after trauma is the don't-miss; that's a bleeding-risk emergency, not an incidentaloma.
The spleen sits up under the left ribs like the quiet kid in the back of class — it almost never raises its hand, so when it finally does, everyone turns around and panics. The good news is that most of the time it's nothing. The spleen's whole career is filtering blood and managing immune cells, and that day job explains nearly everything that goes wrong with it.
Why the spleen even gets lesions
Think of the spleen as the body's blood laundromat: every red cell eventually tumbles through, gets inspected, and the worn-out ones get pulled. Because it's so vascular and so connected to the bloodstream, the spleen tends to collect whatever the blood is carrying — infection seeds, tumor cells, little clots that wedge in and cause infarcts. So when you see a splenic lesion, the question is rarely "what bizarre thing is this?" and more often "is this the boring local thing, or did the blood deliver something I should care about?"
The benign regulars (most of what you'll see)
By a wide margin, splenic lesions are benign and incidental — found while you were actually looking at something else, like the pancreas or kidney.
| Lesion | The quick mental picture | Imaging tell |
|---|---|---|
| Simple cyst | A water balloon parked in the spleen | Round, fluid-density, no enhancement, thin or imperceptible wall |
| Hemangioma | A tangle of slow blood-filled spaces (the spleen's most common benign tumor) | Often shows enhancement; can look similar to its liver cousin |
| Infarct | A wedge of spleen that lost its blood supply | Classically a peripheral wedge, pointing inward, that doesn't enhance |
| Calcified granuloma | An old, healed scar from a prior infection | Tiny, dense, bright fleck — basically a fossil |
That wedge-shaped infarct is worth memorizing. The spleen's blood supply branches like a fan, so when one branch clots off, the dead zone is shaped like a pizza slice with the point aimed at the center. Once you've seen one, you'll never un-see it.
The stripey-spleen trap
Here's a classic rookie mistake. On contrast CT in the early (arterial) phase, the normal spleen enhances in an uneven, swirling, zebra-stripe pattern — bright and dark bands mixed together. This is just normal blood flowing through the red and white pulp at different speeds, and it evens out a few seconds later on the venous phase.
Do not call that arterial-phase zebra pattern a "lesion" or a laceration. The fix is simple: look at the slightly later (portal venous) phase, where a normal spleen turns smooth and uniform. A true lesion stays abnormal across phases; normal stripey enhancement does not. (Understanding why hinges on how contrast timing changes what you see on CT.)
When the spleen earns your worry
A single benign-looking cyst in a well patient is a shrug. The picture changes when you see multiple lesions, especially in someone who is unwell.
- Infection (abscesses or microabscesses): scattered small lesions, often in a patient with fever or a weakened immune system. The blood delivered the bugs; the spleen got seeded.
- Metastases and lymphoma: the spleen is lymphoid tissue, so lymphoma loves it — sometimes as discrete masses, sometimes just a uniformly enlarged spleen. Solid-organ cancers can spread here too, though the spleen is a less common landing spot than the liver.
Multiplicity plus a sick patient is the combination that should move "benign incidentaloma" down your list and "infection or malignancy" up it. Context — fever, known cancer, immune status — does a lot of the diagnostic heavy lifting here.
The don't-miss: trauma
The spleen is the organ most likely to bleed after blunt abdominal trauma — a kick, a handlebar, a car crash. It's a soft, blood-engorged sponge with a thin capsule, so it tears easily and bleeds enthusiastically. On a trauma CT you're hunting for a laceration (a dark cleft through the parenchyma), surrounding blood, and the scary one: active contrast extravasation, which is a little jet of contrast escaping the vessels — meaning it's bleeding right now.
A shattered or actively bleeding spleen after trauma is a surgical and interventional emergency, not an incidental finding. This is the one splenic picture where the clock matters.
How to keep it straight
If you remember nothing else: the spleen is a blood filter, so it catches whatever the blood is carrying. One quiet lesion in a well patient is almost always benign — a cyst, a hemangioma, an old infarct. Many lesions in a sick patient, or any lacerated bleeding spleen after trauma, is where you lean forward and start making phone calls.