What is the approach to assessing steatorrhea?

Assessment of Steatorrhea

Faecal elastase-1 is the preferred first-line test for assessing steatorrhea in clinical practice, requiring only a single 100 mg stool sample with normal values >200 μg/g, mild-moderate insufficiency 100-200 μg/g, and severe insufficiency <100 μg/g. 1

Initial Clinical Evaluation

Key Historical Features to Identify

• Stool characteristics: Bulky, pale/light-colored, malodorous, floating stools that are difficult to flush 2
• Associated symptoms: Flatulence, bloating, dyspepsia, urgency, cramping abdominal pain, and unintentional weight loss 2
• Risk factors: History of chronic pancreatitis, pancreatic surgery, extensive small bowel resection, celiac disease, or cystic fibrosis 3, 2
• Medication review: Magnesium-containing products, NSAIDs, antibiotics, and antiarrhythmics can cause diarrhea mimicking steatorrhea 3

Important caveat: Clinical assessment by stool inspection alone is unreliable—milder forms of malabsorption may not produce visibly abnormal stools 1, 2

Diagnostic Testing Algorithm

First-Line Laboratory Tests

Perform these initial blood tests before invasive procedures 1:

• Complete blood count, C-reactive protein, electrolytes, liver function tests 4
• Iron studies, vitamin B12, folate, thyroid function 1
• Serum anti-tissue transglutaminase IgA with total IgA to screen for celiac disease (the most common small bowel enteropathy) 3, 4
• Consider fat-soluble vitamin levels (A, D, E, K) if malabsorption suspected 2

Stool Testing

Faecal elastase-1 is the preferred pancreatic function test because it is stable in stool for up to a week at room temperature, unaffected by enzyme therapy or diet, and requires only a single sample 1. The test has:

• Sensitivity of 73-100% and specificity of 80-100% for moderate to severe pancreatic insufficiency 1
• Poor sensitivity (<60%) for mild pancreatic insufficiency 1
• Cannot reliably distinguish pancreatic from non-pancreatic malabsorption 1

Interpretation 1:

• Normal: 200-500 μg/g
• Mild-moderate insufficiency: 100-200 μg/g
• Severe insufficiency: <100 μg/g

Important pitfall: Faecal elastase can be falsely low in watery diarrhea from any cause due to dilution, so interpret cautiously in non-formed stools 1

When Three-Day Faecal Fat Is Considered

The quantitative 72-hour faecal fat collection is no longer routinely performed in UK laboratories because it is laborious and unpleasant 1. However, when available:

• Requires diet of known fat content (typically 100 g/day) for 5 days with stool collection during final 3 days 2
• Steatorrhea defined as >7% of ingested fat in stool or coefficient of fat absorption <93% 2
• Severe steatorrhea: >13 g/day (47 mmol/day), most frequently from pancreatic exocrine insufficiency 1, 3

This test has been largely replaced by faecal elastase and imaging in routine practice 1.

Alternative Stool Tests (Limited Use)

• Acid steatocrit: Can be performed on random spot stools with 100% sensitivity and 95% specificity compared to 72-hour quantitative fat, but requires specialized equipment 5
• Stool chymotrypsin: Replaced by faecal elastase due to greater stability 1
• Microscopy (Sudan stain): Qualitative only, with sensitivity of 78% and specificity of 70% 5

Distinguishing Pancreatic from Small Bowel Causes

Clinical Clues

Pancreatic insufficiency typically presents with 3, 2:

• Severe steatorrhea (>13 g/day fecal fat) 1, 3
• History of chronic pancreatitis (symptoms develop 10-15 years after onset), pancreatic carcinoma, or cystic fibrosis 1, 3
• Requires ~90% destruction of pancreatic acinar tissue before symptoms evident 3

Small bowel disease typically presents with 3:

• Milder steatorrhea (<13 g/day) 1
• Positive celiac serology 3
• Evidence of mucosal inflammation on endoscopy/biopsy 3

Important limitation: Fecal fat concentration does not reliably differentiate pancreatic from intestinal steatorrhea despite earlier suggestions—there is significant overlap 6

Imaging and Endoscopic Evaluation

When to Pursue Imaging

If faecal elastase suggests pancreatic insufficiency or clinical suspicion is high 1:

• CT or MRI to evaluate for chronic pancreatitis or pancreatic carcinoma 1
• Endoscopic ultrasound (EUS) for early/mild disease when other imaging is negative 1
• MRCP for ductal evaluation 1

When to Pursue Endoscopy

If celiac serology is positive or faecal elastase is normal but steatorrhea persists 1:

• Upper endoscopy with distal duodenal biopsies to diagnose celiac disease or other small bowel enteropathies 1
• Colonoscopy (age-stratified: full colonoscopy if >45 years, flexible sigmoidoscopy if younger without alarm features) to exclude inflammatory bowel disease 1, 4

Additional Tests for Specific Scenarios

Bile acid malabsorption (terminal ileal disease/resection) 1:

• SeHCAT testing (where available) is sensitive for bile acid malabsorption 1
• Serum 7α-hydroxy-4-cholesten-3-one (rarely performed) 1
• Therapeutic trial of cholestyramine if testing unavailable 1, 2

Small bowel bacterial overgrowth 1, 4:

• Glucose hydrogen breath test (preferred) or lactulose breath test 1, 4
• Consider in patients with risk factors: diabetes, scleroderma, prior surgery, or motility disorders 3, 4

Practical Clinical Approach

1. Start with history and basic labs including celiac serology 1, 4
2. Order faecal elastase-1 as first-line stool test for suspected steatorrhea 1
3. If faecal elastase <100 μg/g: Pursue pancreatic imaging (CT/MRI/EUS) 1
4. If faecal elastase normal but symptoms persist: Consider upper endoscopy with duodenal biopsies to exclude celiac disease or other enteropathies 1
5. If both negative: Consider bile acid malabsorption testing or empirical trial of cholestyramine, and evaluate for small bowel bacterial overgrowth 1, 4

Critical pitfall to avoid: Do not initiate pancreatic enzyme replacement therapy without appropriate testing, as this may mask other treatable disorders such as celiac disease 2