Is there any relation between ibd and celiac disease? how is celiac diagnosed? ( since i think colonoscopy is for large intestine only? )

Yes: There is a relation, one autoimmune disease can cause another to occur. To be tested for celiac, there are blood tests and a upper intestinal biopsy of the small intestines performed by a gastroenterologist.

Similar symptoms: Ibd and celiac disease have been reported together in some patients. Some patients with ibd have also reported a relapse in symptoms on gluten free diet, but a direct relationship has not been definitively established. Celiac disease is diagnosed with the combination of upper endoscopy, duodenum (small intestine) biopsy, and blood test for celiac antibodies.