My 15 Year Old Son, Sudden Onset Of Severe Pain

My 15 year old son, sudden onset of severe pain near umbilicus radiating to genitals. Occurs only with sit/stand, twisting, flexing of abdominal muscles ie..urinating, bowel movements. Occurred 1 yr. Ago & resolved on own. He's a competitive weight lifter, track, bball, & fball. Dr. Visit today. No fever or other symptoms. Said umbilical hernia although no bulge present now or previous. Is this possible? If not, other diagnoses to consider?