The medical term for this condition is “splenomegaly.” It’s a condition where a patient has a larger-than-normal spleen, as the name implies. The spleen is a vital organ located under the left ribcage and is crucial in filtering blood and fighting infection.  Around 3% of the general population are living with an enlarged spleen. However, an enlarged spleen can also be a symptom of the infectious viral disease, mononucleosis (mono). While it is not permanent, people with mono may experience an enlarged spleen for up to four to six weeks. Around 50% of persons with mono suffer from an enlarged spleen. While there are no typical telltale symptoms, splenomegaly can cause pain in the left upper belly, lower your red blood count, and increase vulnerability to rapid infections. As the spleen gets bigger, it can press against your stomach, making you feel full even without eating.