Use of whole gut perfusion to investigate gastrointestinal blood loss in patients with iron deficiency anaemia

Iron deficiency anaemia may be due to occult bleeding into the gut. However, although clinical investigations may show a high frequency of gastrointestinal tract disease in these patients, the cause-effect relationship between the lesions detected and anaemia remain uncertain. This study aimed to establish whether lesions detected by endoscopy or imaging of the gastrointestinal tract in patients with unexplained iron deficiency anaemia are bleeding continuously. Routine clinical tests were performed in 42 patients with unexplained iron deficiency anaemia referred to this unit. Whole gut lavage and assay of haemoglobin in the gut perfusate were also performed. The main outcome measures were clinical diagnoses (by imaging and endoscopy of the upper gastrointestinal tract and colon); the concentration of haemoglobin in whole gut lavage fluid; and the calculated gastrointestinal blood loss per day. There were 73 clinical, dietary, or iatrogenic factors of possible aetiological importance in the 42 patients - poor diet (10), gross gastrointestinal abnormality (34 in 28 patients), malabsorption (14), coagulation problems (6), and NSAID use (9). The gut lavage test showed, however, that at the time the test was performed, only eight patients were losing more than 2 ml blood daily into the gut, including all four with colonic cancer, one with diffuse gastric vascular ectasia, and one with severe ulcerative oesophagitis. It is concluded that occult gastrointestinal bleeding sufficient to cause anaemia was evident in only 19% of 42 patients. There was a high frequency of other potential causes of iron deficiency in the remainder, suggesting that most of the gastrointestinal diseases and lesions detected in them were probably coincidental. Factors other than blood loss should be considered and treated in patients referred for anaemia assessment.