Your spleen is an organ above your stomach and under your ribs on your left side and helps control the amount of blood in your body. If it's enlarged ... and bursts, you could potentially die from blood loss.
Certain diseases might cause your spleen to swell. You need a diagnosis, so yes...it's an emergency. Go see a doc.
P.S. Doctors only answer if you click on the "ask a Doctor" button to the right of the screen.