@michelle- doesn't it depend on whether it's grumbling or acute? I had grumbling appendicitis for years in my teens before the doctors realised what it was. Admittedly I don't think I could have contemplated playing tennis during an attack but they didn't always last that long. If it's acute, yes he should be in hospital now!
I agree. I had a grumbling appendix for a while when i was young before it was taken out. There's no way I could have done anything strenuous. Acute appendicitis is a medical emergency.