Can riding on a commerical lawnmower for a long period of timecause stomach intestine problems

My son has a severe problem in the intestinal area.  He has had a Ct scan which shows the small intestine thicken and inflammation.  He has a CBCc's upper Gi and lower Gi series.  He has had an Colonoscopy and Endoscopy.  All test are negative except for the abnormal CT Scan.  Is it possible that his job; he is a foreman for a landscaping company.  Is it possible that standing on a commerical lawn mower or handling a commerical blower can cause damage to his intestines?  He has lost 15 lbs. in one month because he dosen't eat to avoid the pain.  The pain feels like someone is twisting or squeezing his intestine.  Are you or anyone you know familiar with this problem? Please advise Tu Mary