My 16 Yo Daughter Was Running On The Treadmill Last

My 16 yo daughter was running on the treadmill last evening and suddenly felt a "pop" and then severe abdominal pain in her right upper quadrant. I initially thought that she pulled a muscle which i thought was odd as she is an athlete. Tonight the pain continues and she states she had diarrhea this morning associated with foul gas. I am a little more concerned now. Any ideas?