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Related Subjects: |Ulcerative Colitis |Microscopic colitis |Irritable bowel syndrome |Lower Gastrointestinal (Rectal) Bleeding

Malabsorption in the small intestine is a complex condition requiring a comprehensive diagnostic approach and tailored management strategies.

Small Bowel disease

• Coeliac disease: Autoimmune destruction of the small bowel mucosa in response to gluten, leading to villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis.
• Tropical sprue: Chronic diarrhoeal condition, likely of infectious etiology, leading to villous flattening and malabsorption in the small intestine.
• Giardiasis: Infection with Giardia lamblia that adheres to the small intestine, disrupting nutrient absorption.
• Whipple's disease: A rare bacterial infection (Tropheryma whipplei) that affects the intestinal mucosa, causing villous atrophy and malabsorption.
• Radiation enteritis:Damage to the intestinal mucosa following radiation therapy, causing fibrosis, ischaemia, and resultant malabsorption.
• Short Bowel Syndrome: Resulting from surgical resection of significant portions of the small intestine, reducing absorptive surface area.
• Small Intestinal Bacterial Overgrowth (SIBO): Excessive bacteria in the small intestine that disrupt normal digestion and nutrient absorption.
• Crohn’s Disease: Chronic inflammatory condition that can cause segmental involvement of the small intestine, leading to malabsorption through strictures, fistulae, and mucosal damage.
• Pancreatic Insufficiency: Seen in chronic pancreatitis, cystic fibrosis, or pancreatic carcinoma, leading to inadequate production of digestive enzymes, particularly lipase, amylase, and proteases.
• HIV-related Enteropathy: Direct infection of the gastrointestinal tract or opportunistic infections leading to malabsorption.

Terminal Ileal disease

• Impaired B12 uptake receptors:
• Bile salts uptake receptors

Clinical

• Chronic diarrhea, often steatorrhea in fat malabsorption.
• Abdominal bloating, cramping, and excessive gas.
• Weight loss despite adequate caloric intake.
• Calcium and Vitamin D loss: Osteoporosis, tetany
• B12 loss Macrocytic anaemia, glossitis, neuropathy.
• Iron loss: Microcytic anaemia, fatigue.

Investigations

• Microcytic anaemia - Iron deficiency and Macrocytic anaemia - Folate and Iron deficient. Dimorphic is both
• Low albumin, low calcium and phosphate, macrocytic hypochromic anaemia, Low ferritin (iron deficiency)
• Low folate and B12 due to malabsorption
• Low calcium and raised alkaline phosphatase (Vitamin D and Calcium malabsorption)
• Prolonged PT due to Vitamin K deficiency
• Stool Analysis: Qualitative fecal fat (Sudan stain), quantitative fecal fat (72-hour collection), stool elastase (for pancreatic insufficiency), stool pH, and reducing substances.
• Blood Tests: FBC, serum electrolytes, albumin, prealbumin, iron studies, vitamin levels (B12, D, E), prothrombin time (PT), and thyroid function tests.
• Serologic Tests: Tissue transglutaminase (tTG) antibodies for coeliac disease, antigliadin antibodies, anti-Saccharomyces cerevisiae antibodies (ASCA) for Crohn’s disease.
• Breath Tests: Lactose intolerance (hydrogen breath test), SIBO (glucose or lactulose breath test).

Imaging

• Upper Endoscopy with Biopsy: mucosal causes such as coeliac disease, Whipple’s disease, and tropical sprue.
• Small Bowel Follow-Through or MR Enterography: Useful for structural abnormalities, strictures, or Crohn’s disease.
• CT or MRI: pancreatic pathology, lymphatic abnormalities, and abdominal masses.

Specific Managment

• Coeliac Disease: Lifelong gluten-free diet.
• Crohn’s Disease: Immunosuppressants, biologics, and possibly surgery.
• Pancreatic Insufficiency: Pancreatic enzyme replacement therapy (PERT).
• SIBO: Antibiotics (e.g., rifaximin), prokinetics.
• Lactose Intolerance: Lactose-free diet or enzyme replacement.

General Managment

• Dietary Modification: Tailored to specific deficiencies; low-fat diet in fat malabsorption, lactose-free diet, gluten-free diet.
• Supplementation: Oral or parenteral vitamins and minerals based on specific deficiencies (e.g., B12, iron, calcium, fat-soluble vitamins).
• Caloric Support: In severe cases, enteral nutrition (e.g., elemental diets) or parenteral nutrition may be necessary.