The spleen is a fist-sized organ tucked behind the rib cage on the left side of the body. When it enlarges (medically known as splenomegaly), it can cause a dull, aching pain under the left rib cage.

There are 24 ribs in total, 12 on each side of the body. The following are emergency causes of pain under the left rib cage: Heart Attack A heart attack occurs when blood flow to the heart is ...