<s>[INST] my son has been having severe ab pain while running. He runs cross country and two miles into the race he develops a horrible pain in his side, right below the rib cage and a little lower down. We thought he was getting side stitches but I think its more than that. [/INST] Hi.Thanks for your query. Getting severe pain in abdomen on running and particularly below the rib cage and a little lower down is indicative of a certain inflammatory process going on in the abdomen which needs proper evaluation:I would advise the following:CT scan of the abdomen and relevant tests of blood, urine and stool should help you to get the diagnosis and a plan for further treatment... </s>