How do I know if I have a malabsorption issue?

How to Identify Malabsorption Issues

The most effective way to identify malabsorption is through a systematic diagnostic approach that includes screening blood tests, specific antibody testing, and targeted endoscopic evaluation with biopsies when indicated. 1, 2

Initial Screening Tests

• Full blood count, erythrocyte sedimentation rate, C-reactive protein, electrolytes, liver function tests, calcium, vitamin B12, folate, iron studies, and thyroid function tests should be performed as first-line screening - these have high specificity but low sensitivity for organic disease 1, 2
• Stool cultures and microscopy should be performed to rule out infectious causes, even though these are uncommon in immunocompetent patients with chronic symptoms 1
• Confirmation of true diarrhea through stool inspection and measurement is recommended before pursuing extensive malabsorption workup 2

Specific Testing for Common Causes

Celiac Disease

• Antiendomysium antibody testing is the preferred first-line test for celiac disease, which is the most common small bowel enteropathy in Western populations 1, 3, 2
• If serological tests are negative but small bowel malabsorption is still suspected, upper gastrointestinal endoscopy with distal duodenal biopsies should be performed 1, 3

Pancreatic Insufficiency

• Newer specific tests such as stool elastase are preferred over older methods like quantification of three-day fecal fat 1, 2
• Pancreatic enzyme treatment should not be used as a diagnostic trial due to expense and variable efficacy without proper dose adjustment 1

Fat Malabsorption

• Traditional three-day fecal fat quantification is poorly reproducible, unpleasant, and non-diagnostic - its use is discouraged 1, 2
• Breath tests for fat malabsorption (using 14C-triolein or 13C-labeled mixed triglyceride) may serve as alternatives to fecal fat collection but have low sensitivity for mild/moderate fat malabsorption 1

Carbohydrate Malabsorption

• Carbohydrate malabsorption is predominantly associated with mucosal disease or dysfunction 1
• Hydrogen breath tests offer better diagnostic value for specific carbohydrate intolerances than stool pH or reducing substances 2

Specialized Testing Based on Clinical Suspicion

Bile Acid Malabsorption

• Consider bile acid malabsorption in patients with IBS-D who have atypical features such as nocturnal diarrhea or prior cholecystectomy 1, 4
• SeHCAT nuclear medicine test is the de facto gold standard for diagnosing bile acid malabsorption but is not available in all countries 1
• Blood tests measuring C4 and FGF19 can be used where available 1

Small Bowel Imaging

• Small bowel imaging (barium follow-through or enteroclysis) should be reserved for cases where small bowel malabsorption is suspected and distal duodenal histology is normal 1
• Technetium HMPAO-labeled white cell scanning can be used to examine for intestinal inflammation 1

Important Clinical Pitfalls

• Factitious diarrhea becomes increasingly common in specialist referral practice - screening for laxative abuse should be performed early in the investigation 1
• Patients should not restrict their diets before testing for malabsorption syndromes as this may affect diagnostic accuracy 5
• Malabsorption may present with subtle extraintestinal manifestations (anemia, osteoporosis, neurological symptoms) without obvious gastrointestinal symptoms 6, 7
• In patients under 45 years with typical symptoms of functional bowel disorder and negative initial investigations, a diagnosis of IBS may be made without further investigations 1

When to Refer to Gastroenterology

• Referral is warranted when there is diagnostic doubt, symptoms are severe or refractory to first-line treatments, or the patient requests specialist opinion 4
• Patients with documented diarrhea who are under 45 years with atypical and/or severe symptoms should have further evaluation beyond initial screening 1

Remember that malabsorption can be caused by numerous disorders affecting the small intestine, pancreas, liver, biliary tract, and stomach, requiring a targeted diagnostic approach based on clinical presentation and initial test results 6.