lower abdominal pain

My 14 year old son started complaining  of lower abdominal pain 6 days ago. The pain comes and goes but is worse after eating. He describes the pain as stabbing. It is across the whole lower abdomen but the lower right is tender when pushed on. He also has tenderness on his right lower back.
He has no fever, no vomitting, no constipation and a normal appetite. His bowel movements are normal and regular.
His pediatrician checked for hernia and sent him to all childrens hospital emergency for a CT scan, unrialysis, and blood work. The CT scan showed no stones, normal appendix, no blockages, his hemaglobin was high and white cells low. The urine was neg for blood but did have some protein.
They said he was a little dehydrated and gave him IV fluid. They said he may have already passed a small kidney stone which seemed believable until we left the hospital and got something to eat on the way home. Within 30 minutes of eating he began to have the same pain in his abdomen and it has lasted all evening. It doesn't seem to matter what he eats- the pain comes in response to solid food in his digestive tract.
I am wondering about the posibility of a parasite but the research I've done on the internet doesn't discuss lower abdominal pain as the only symptom.
I am hoping someone out there can help me!!!!!!!

[Kevin Pho, MD]

I agree with the CT scan, which can exclude a blockage or colitis.  

If negative, as it appears to be the case, the next steps to consider would be to send the stool off for culture and analysis, as well as an evaluation for malabsorption.

I would also consider a colonoscopy, which can comprehensively look at the lower bowel, as well as blood tests to look for celiac disease.

These options can be discussed with your personal physician, or in conjunction with a pediatric gastroenterologist.

This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.

Kevin Pho, M.D.
www.kevinmd.com
www.twitter.com/kevinmd

[kim944]

Thank you. The pediatric gastroenterologist has ordered all the tests you mentioned.

Is it possible that this could be a virus? The reason I ask is that the symptoms seem to have disappeared as quickly as they started. Yesterday afternoon he ate, had no pain or cramping the again last night- ate with no pain or cramping afterward.
The symptoms started one week ago and seem to have now stopped abruptly.