I suggest that you schedule an appointment with you primary care physician
. Generally speaking, there are a few reasons why do not think that this is a spleen rupture. First, let's say that you did catch mononucleosis from your friend that you shared a drink with. It takes a few days for the infection is set in and much longer for you to develop splenomegaly. Splenomegaly is the term we use to describe an enlarged spleen. In addition, people that have mononucleosis generally do not develop splenic rupture unless they also suffer from trauma to the abdomen. This is why we recommend people that get mononucleosis avoid contact sports. Another reason why I do not think that this is spleen rupture is that rupture of the spleen generally causes massive abdominal bleeding
and is often life-threatening and deadly. A small amount of pain over the left rib cage is usually not what people complain of when the complain that their spleen ruptured. They often become unconscious quickly from loss of blood. Certainly I think that your left-sided abdominal or left-sided rib cage pain should be worked up. I suggest that you schedule an appointment with you primary care physician. He or she can perform a physical exam and potentially determine why you are having this pain. Good luck.