The International Intestinal Failure Registry (IFR) is an initiative of the Intestinal Rehabilitation and Transplant Association (IRTA) and The Transplantation Society (TTS) and will be managed by these organizations. The primary objective of this project is to create a large international database of children with intestinal failure to characterize their management and outcome and guide the development of best practices and evidence-based management.

The primary objective of this project is to create a large international database of children with intestinal failure to characterize their management and outcome and guide the development of best practices and evidence-based management.

Iron deficiency is the most common type of nutritional deficiency in the world and is unique in that it affects both developing and developed countries. The most common complication of iron deficiency is anemia (a low level of iron in the red blood cells). Although patients with anemia may not have any symptoms, many patients with anemia do have problems such as fatigue, tiredness, shortness of breath and/or pale skin.

Study participants will undergo some evaluations in addition to their regular anemia work up. These include the following:
1) Questionnaires;
2)Iron absorption test consisting of 3 blood samples over the span of 3 hours after having drank a liquid iron solution.
3) stool and urine sample collection.
4) food diary to monitor iron dietary intake.
5)If an upper endoscopy is also part of the participant's standard of care workup, the study team will ask the endoscopist to take an additional biopsy sample to test for one of the proteins that is responsible for taking up iron from your food into the intestine.

Participation in this study will last over 2 visits lasting 1 to 4 hours each. The two visits should fall within the span of 1 month of each other.

Risks associated with this study include side effects of oral iron supplement ingestion. This oral iron may have a metallic taste. In some patients, it could even cause nausea or vomit, abdominal gas or abdominal discomfort. We also ask to draw blood and blood withdrawal may have side effects including bruising, pain, bleeding or rarely infection at the puncture site. Confidentiality breach is also a risk.

There are no direct benefits to the participant. However, this study will help advance diagnosis and clinical assessments of iron deficiency anemia.

The alternative is to not participate in the study and continue regular iron deficiency anemia work up exclusively with the treating physician and medical team.