I have a bump under my left rib cage where spleen is. it's pretty large. the doctor thinks i have mono. is it normal to see the swollen spleen?

No : Not common to see swollen spleen, except when massively enlarged.

Confusing question: If you can feel a bulge under your left rib cage it could be a swollen spleen.You would usually never feel one as it is usually tucked down close to the kidney and deep in the abdomen. Mono has many symptoms and a swollen spleen is one of them.You should avoid any physical activity that could increase the risk of trauma to the spleen (horseriding, bicycle riding etc.).