Oily stool (steatorrhea) may be a sign your body is not properly digesting the fat you consume. There are many reasons this could happen.
Causes of oily stools include:
- Conditions leading to exocrine pancreatic insufficiency (EPI)
- Chronic pancreatitis
- Cystic fibrosis (CF)
- Conditions resulting in pancreatic duct obstruction or resection of the pancreas such as pancreatic tumors
- Bile acid deficiency states
- Cholestasis e.g., primary biliary cholangitis (PBC)
- Primary sclerosing cholangitis
- Inability to absorb bile acids in the distal ileum resulting in diminished bile acid pool
- Ileal resection
- Crohn’s disease of the ileum
- Small intestinal bacterial overgrowth (SIBO)
- Diseases affecting the small intestine
- Celiac disease
- Tropical sprue
- Giardiasis
- Whipple disease
- Lymphoma
- Amyloidosis
- SIBO
- HIV enteropathy
- Uncommon causes
- Use of lipase inhibitors such as orlistat (Xenical, Alli)
- Zollinger-Ellison syndrome
- Graft-versus-host disease
What Are Symptoms of Oily Stools?
Symptoms of oily stools (steatorrhea) may include stool that is:
- A greasy or oily consistency
- Difficult to flush/tends to float
- Bulky
- Pale
- Foul-smelling
Other symptoms that may accompany oily stools depend on the cause and can include:
- Chronic diarrhea
- Abdominal discomfort or pain
- Bloating
- Weight loss
- Growth failure and delayed puberty in children
- Loss of subcutaneous fat and muscle wasting in severe cases
- Fat-soluble vitamin (A, D, E, and K) deficiencies
- Anemia
- Oral ulcers
- Dermatitis herpetiformis rash
- Yellowing skin and eyes (jaundice)
- Fatigue
- Itching
How Are Oily Stools Diagnosed?
Oily stools (steatorrhea) are diagnosed with a patient history and physical examination. Tests used to help determine the cause of oily stools may include
- Fecal testing for fat content in stool
- Abdominal X-ray
- Computerized tomography (CT) scan of the abdomen
- Magnetic resonance imaging (MRI) scan of the abdomen
- Magnetic resonance cholangiopancreatography (MRCP)
- Endoscopic retrograde cholangiopancreatography (ERCP)
- Endoscopic ultrasound (EUS)
- Blood tests
- Serum tissue transglutaminase IgA antibodies (TTG-IgA)
- Liver tests
- Biopsy
- Endoscopy with small intestinal biopsy
- Liver biopsy
What Is the Treatment for Oily Stools?
Treatment for oily stools (steatorrhea) depends on the underlying cause.
Treatment for exocrine pancreatic insufficiency (EPI) may include:
- Pancreatic enzyme replacement therapy (PERT)
- Normal to a high-fat diet
- Fat-soluble vitamin supplementation
Treatment for small intestinal bacterial overgrowth (SIBO) may include:
Treatment for celiac disease may include:
- Diet-centered recommendations including a strict life-long gluten-free diet
- Education about the disease
- Management of nutritional deficiencies
- Consultation with a dietitian knowledgeable in celiac disease
Treatment for primary biliary cholangitis (PBC) may include:
- Ursodeoxycholic acid
- Liver transplant
From 
Image source: iStock Images
https://www.ncbi.nlm.nih.gov/books/NBK541055/