An enlarged spleen is usually detected during a physical exam. Your doctor can often feel it by gently examining your left upper abdomen. However, in some people — especially those who are slender — a healthy, normal-sized spleen can sometimes be felt during an exam.

Your doctor may confirm the diagnosis of an enlarged spleen with one or more of these tests:

  • Blood tests, such as a complete blood count to check the number of red blood cells, white blood cells and platelets in your system
  • Ultrasound or computerized tomography (CT) scan to help determine the size of your spleen and whether it's crowding other organs
  • Magnetic resonance imagining (MRI) to trace blood flow through the spleen

Imaging tests aren't always needed to diagnose an enlarged spleen. But if your doctor recommends imaging, you generally don't need any special preparation for an ultrasound or MRI.

If you're having a CT scan, however, you may need to refrain from eating before the test. If you need to prepare, your doctor will let you know well in advance.

Finding the cause

Sometimes you may need more testing to find the cause of an enlarged spleen, including liver function tests and a bone marrow exam. These tests can provide more-detailed information about your blood cells than can blood drawn from a vein.

A sample of solid bone marrow is sometimes removed in a procedure called a bone marrow biopsy. Or you may have a bone marrow aspiration, which removes the liquid portion of your marrow. In many cases, both procedures are performed at the same time (bone marrow exam).

Both the liquid and solid bone marrow samples are usually taken from the pelvis. A needle is inserted into the bone through an incision. You'll receive either general or local anesthesia before the test to ease discomfort.

A needle biopsy of the spleen is very rare because of the risk of bleeding.

Occasionally, your doctor may recommend surgery to remove your spleen when there's no identifiable cause for the enlargement. After surgical removal, the spleen is examined under a microscope to check for possible lymphoma of the spleen.