What causes steatorrhea?

Causes of Steatorrhea

Steatorrhea results from either pancreatic exocrine insufficiency (most common cause of severe steatorrhea) or small bowel malabsorption disorders, with pancreatic causes typically producing the highest fecal fat content. 1, 2

Pancreatic Causes

Pancreatic exocrine insufficiency is the leading cause of severe steatorrhea (>13 g/day fecal fat) and requires approximately 90% destruction of pancreatic acinar tissue before symptoms become evident. 1, 2

Primary Pancreatic Disorders

• Chronic pancreatitis is the most common pancreatic cause in adults, with progressive destruction of both islet cells and acinar tissue leading to maldigestion of fats. 1
• Pancreatic carcinoma causes steatorrhea through obstruction and destruction of pancreatic tissue. 1
• Cystic fibrosis results in pancreatic insufficiency in >80% of patients at diagnosis, increasing to >90% with age, due to CFTR gene mutations affecting chloride transport and causing thick mucus that obstructs pancreatic ducts. 1

Key Clinical Pearl

Patients with pancreatic insufficiency have deficient chloride transport and virtually absent pancreatic enzyme activity, leading to fat and protein malabsorption with characteristic loose, foul-smelling fatty stools and abdominal pain. 1

Small Bowel Causes

Mucosal Disorders

• Celiac disease is the most common small bowel enteropathy in the Western world (prevalence 1:200-1:559), presenting with steatorrhea due to villous atrophy and decreased absorptive surface. 1, 2
• Crohn's disease causes steatorrhea through mucosal inflammation, reduced absorptive surface, and potential bacterial overgrowth. 1, 2
• Other enteropathies including Whipple's disease, tropical sprue, amyloid, and intestinal lymphangiectasia can produce malabsorption and steatorrhea. 1

Bile Acid-Related Causes

• Bile acid malabsorption occurs with terminal ileum disease or resection, leading to insufficient bile acids for fat emulsification and micelle formation. 1, 2
• Post-cholecystectomy diarrhea develops in up to 10% of patients through increased gut transit, bile acid malabsorption, and increased enterohepatic cycling. 1

Bacterial and Infectious Causes

• Small bowel bacterial overgrowth causes steatorrhea through bile acid deconjugation and direct mucosal damage, commonly occurring after gastric surgery or in conditions with intestinal stasis. 1, 2
• Giardiasis and other chronic infections can produce persistent steatorrhea through mucosal inflammation and malabsorption. 1

Surgical Causes

• Extensive small bowel resections (particularly ileum and right colon) lead to steatorrhea due to lack of absorptive surface, decreased transit time, and bile acid malabsorption. 1, 2
• Bariatric surgery can result in steatorrhea with subsequent deficiencies in fat-soluble vitamins, zinc, copper, and magnesium. 2
• Gastric surgery including bypass procedures predisposes to bacterial overgrowth and rapid transit, both contributing to fat malabsorption. 1

Endocrine and Systemic Causes

• Hyperthyroidism causes diarrhea and potential steatorrhea through endocrine effects on gut motility and rapid transit. 1
• Diabetes mellitus produces steatorrhea via multiple mechanisms: autonomic neuropathy affecting gut motility, small bowel bacterial overgrowth, bile acid malabsorption, and decreased pancreatic function. 1

Other Important Causes

Medications and Substances

• Alcohol abuse causes steatorrhea through rapid gut transit, decreased intestinal disaccharidase activity, and direct pancreatic damage. 1
• Medications account for up to 4% of chronic diarrhea cases, particularly magnesium-containing products, NSAIDs, antibiotics, and antiarrhythmics. 1

Miscellaneous

• Disaccharidase deficiency (particularly lactase deficiency) can contribute to malabsorption symptoms. 1
• Radiation enteritis causes chronic mucosal damage with subsequent malabsorption. 1
• Mesenteric ischemia reduces absorptive capacity through chronic mucosal hypoperfusion. 1

Critical Diagnostic Distinction

Fecal fat concentration averages 15.0 g% in pancreatic steatorrhea versus 8.9 g% in intestinal causes, though significant overlap exists (42% of pancreatic patients have <10 g%), making this measurement insufficient for definitive differentiation. 3 Fecal elastase-1 testing (<100 mg/g consistent with exocrine pancreatic insufficiency) is the preferred non-invasive diagnostic approach. 2