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EXECUTIVE SUMMARY

Background

● Colonic cancer, gastric cancer and coeliac disease are the most important gastrointestinal causes of iron deficiency anaemia.

Definitions

● The lower limit of the normal range should be used to define anaemia (B).
● Iron deficiency should be confirmed by a low serum ferritin, red cell microcytosis or hypochromia in the absence of chronic disease or haemoglobinopathies (A).
● Any level of iron deficiency anaemia should be investigated (B).

Investigations

● Rectal examination and urine testing should be performed (B).
● All patients should be screened for coeliac disease (B).
● Upper and lower GI investigations should be considered in all male patients unless there is a history of significant overt nonGI blood loss (A).
● Upper and lower GI investigation should be considered for female patients who are post-menopausal, aged over 50 years or older, or have a strong family history of colorectal cancer (B).
● Colonoscopy has advantages over barium enema for investigation of the lower GI tract in IDA, but either is acceptable (B).
● Further direct visualisation of the small bowel is probably not necessary unless the IDA is transfusion dependent (B).
● Faecal occult blood testing is of no benefit in the investigation of IDA (B).
● Only post-menopausal women and men aged over 50 years should have GI investigation of iron deficiency without anaemia (C).

Management

● All patients should have iron supplementation both to correct anaemia and replenish body stores (B).
● Parenteral iron can be used when oral preparations are not tolerated (C).

SCOPE

These guidelines are primarily intended for gastroenterologists and GI surgeons but are applicable for other doctors seeing patients with IDA. The investigation of overt blood loss is not considered in these guidelines.

INTRODUCTION

Iron deficiency anaemia (IDA) has a prevalence of 2–5% among adult men and post-menopausal women in the developed world and is a common cause of referral to gastroenterologists (4–13% of referrals). While menstrual blood loss is the commonest cause of IDA in pre-menopausal women, blood loss from the gastrointestinal (GI) tract is the commonest cause in adult men and post-menopausal women. Asymptomatic colonic and gastric carcinoma may present with IDA and seeking these conditions is a priority in patients with IDA. Malabsorption (most frequently from coeliac disease in the UK), poor dietary intake, blood donation, gastrectomy and NSAID use are not uncommon causes of IDA and there are many other possible causes (Table 1). IDA is often multifactorial. The management of IDA is often suboptimal with most patients being incompletely investigated if not at all. Dual pathology, i.e. the presence of significant GI bleeding in upper and lower GI tracts, is uncommon but does occur in 1–10% of patients.

TABLE 1. Causes of iron deficiency anaemia with prevalence as percentage of total4–9

DEFINITIONS

Anaemia

The WHO defines anaemia as a haemoglobin below 13 g/dL in men over 15 years, below 12 g/dL in non-pregnant women over 15 years, and below 11 g/dL in pregnant women. The diagnositic criteria for anaemia in IDA vary between published studies. The normal range for haemoglobin also varies between different populations in the UK. Therefore, it is reasonable to use the lower limit of the normal range for the laboratory performing the test to define anaemia (B).

There is little consensus as to the level of anaemia that requires investigation. The Department of Health referral guidelines for suspected lower GI cancer suggest that only patients with Hb less than 11 g/dl in men or less than 10 g/dl in postmenopausal women be referred, despite there being no supporting evidence.

A cut-off value of 8 g/dL has been shown to be the most discriminatory for detecting patients with and without cancer (regardless of gender), but this value lacks sensitivity9. It is recommended that any level of anaemia should be investigated in the presence of iron deficiency (B).