Splenomegaly

What it means

The spleen sits high in the left upper belly, just under the ribcage. It helps filter old red blood cells out of the bloodstream and plays a role in fighting infection. A normal adult spleen measures up to about 12 cm in length. When it stretches past that, radiologists call it enlarged. On a CT or MRI, the spleen simply looks bigger than it should — sometimes nudging neighbouring organs out of the way.

Why it appears on a CT or MRI report

Reports usually give a measurement in centimetres and sometimes a volume. They may describe the enlargement as mild, moderate, or massive, and note whether the organ has a normal smooth shape or shows nodules, scars, or unusual density. The radiologist often pairs this finding with other clues on the same scan: signs of liver disease, dilated veins around the stomach (varices), enlarged lymph nodes, or changes in the bone marrow. Those neighbours often explain the spleen.

What it usually means

An enlarged spleen has many possible causes, broadly falling into a few groups. Liver-related causes are the most common in adults — when the liver scars, blood backs up through the spleen and stretches it. Infections like glandular fever (mononucleosis), malaria, or hepatitis can swell it temporarily. Blood disorders, including some leukaemias and lymphomas, can enlarge it more persistently. Less commonly, storage diseases and autoimmune conditions are responsible. Mild, isolated enlargement in someone who feels well is often followed up with simple blood tests; marked or rapidly growing enlargement triggers a more thorough work-up. Because the enlarged spleen is fragile, doctors may also advise avoiding contact sports while it is bigger than usual to reduce the risk of injury.

When to follow up

Talk to your doctor about the finding so they can investigate the cause — usually a focused history and some blood tests are the first step. Mention any night sweats, unexplained weight loss, fevers, easy bruising, persistent fullness after small meals, or pain in the left upper belly or left shoulder. Sudden severe left-sided belly pain or signs of internal bleeding (lightheadedness, fast pulse) after even minor trauma deserve emergency attention, because the swollen organ can rupture more easily.

A plain-language way to picture it

Think of the spleen as a sponge that filters the bloodstream. If too much traffic comes through, or if it has to work overtime cleaning up after an infection, it soaks up more material and physically swells. A mildly damp sponge stays soft and harmless; a fully saturated one is heavier, more fragile, and squeezes against everything around it. The size on the scan tells you how saturated the sponge has become.