I found those causes of iron deficiency from many websites and put them together (okay rheumatoid arthritis should not be listed twice lol).
The iron deficiency due to a hiatus hernia is from a cameron lesion located at the neck of a large hiatal hernia. Cameron lesions are seen in 5.2% with a hiatal hernia so it's not common but it is a noted cause of iron anaemia. Cameron lesions may be missed during a endoscopy though.
I'm not sure of what tests you have had so far but non invasive tests include a fecal occult blood test (checking for bleeding in the GI tract) and testing the urine for blood or haemoglobin. An easy baking soda test to check for stomach acidity is something you can try out as well. The info for that test is on another answer of mine....
"Is IBS Real?
In a study recently published in Medical Hypotheses (2011 76(1):97-99), Dr. Habba analyzed 575 patients presenting with previously diagnosed diarrhea predominant IBS (IBS-D). 303 patients completed all the testing and follow up necessary to be included in the results. The study concluded that 98% of these patients had conditions other than the previous diagnosis of IBS.
When these conditions were identified and appropriately treated, 98% of them improved as assessed by fewer than three bowel movements per day. Habba Syndrome constituted 41% of the patients studied, post-cholecystectomy diarrhea 23%, lactose intolerance 8%, microscopic/lymphocytic colitis 7%, celiac disease 4% and several other specific conditions comprised the balance.
This result is very encouraging and is in contrast with the results presently achieved by treating “IBS”. Physicians frequently fall short of “getting to the bottom” of the problem by tagging patients with “IBS”, a vague entity that merely describes their symptoms and usually results in a poor therapeutic outcome.
These findings lead to the theory concluding that there is no IBS-D. Patients need to be evaluated thoroughly until a true clinical entity is found and treated."
"The Cedars-Sinai researchers found that 78% of the IBS patients they tested had what they called small intestinal bacterial overgrowth (SIBO), a condition in which excessive amounts of bacteria are present in the small intestine.
The researchers treated the patients who tested positive for SIBO with a 10-day course of antibiotics. Tests at the end of that time found that 25 of 47 patients had no bacterial overgrowth present, and that 12 of them had no IBS symptoms, while the symptoms were "significantly reduced" in the other 13."