Not sure if this test is done in the US, but you might ask your gastro about it - calprotectin stool assay test.
Non invasive and cheap. If the calprotectin level is out of range (norm is 20, mine has been as high as 80), this shows inflammation somewhere in the GI tract. If high, the gastro can then go ahead with other invasive testing to rule out Crohn's, ulcerative colitis and coeliac. I have Crohn's and have this test done regularly.