Synopsis
Localise malabsorption to luminal digestion, intestinal mucosa, bile acid handling, lymphatic transport or reduced absorptive surface; test for coeliac disease and pancreatic insufficiency correctly; and replace deficits without obscuring the cause.
- Steatorrhoea, chronic diarrhoea, weight loss, bloating, anaemia, oedema, bruising, neuropathy or bone disease may be the presenting phenotype; absence of obvious stool fat does not exclude malabsorption.
- Classify mechanisms: impaired intraluminal digestion, mucosal disease, reduced small-bowel surface, bile acid diarrhoea, lymphatic obstruction or mixed postoperative causes.
- For coeliac testing, the patient must be eating gluten; check total IgA with IgA tissue transglutaminase and use appropriate IgG-based testing in IgA deficiency.
Key red flags
Steatorrhoea, weight loss, diabetes, recurrent pancreatitis, pancreatic surgery or chronic epigastric pain suggests inadequate enzyme delivery; pancreatic cancer must be considered with new symptoms or jaundice.
Investigation priorities
Measure total IgA and IgA tTG, with EMA for weakly positive results and IgG-based testing when IgA deficient according to the current pathway.
Management branches
Chronic diarrhoea, steatorrhoea, weight loss or unexplained nutrient deficiency suggests impaired absorption.
- Confirm stool and weight phenotype, review diet, surgery, pancreas, ileum, medicines, travel and immune state, and assess dehydration or severe deficiency.
- Screen for coeliac disease while gluten is still consumed, inflammation and common deficiencies; add faecal elastase and bile acid testing according to phenotype.
Key medicines
PancreatinDose by lipase units with all meals and snacks, titrating to meal fat content, symptoms and weight under the current BNF and pancreatic specialist pathway; higher requirements may need acid suppression review.
Vitamin B12 replacementUse current BNF cause-specific oral or intramuscular hydroxocobalamin regimens; neurological involvement requires an urgent loading schedule and specialist follow-up.