What is bowel cancer?

Jonny had always been fit and healthy. He ate well, exercises, and looks after himself. Jonny then got stomach cramps. A mate at work had just had stomach cramps and been to the doctor, they lasted a couple of weeks and he had the all clear so Jonny assumed that he was experiencing the same bug etc. The cramps fluctuated in intensity over a period. After realising that he had been having the cramps for 3 months he went to the doctor.