Diseases of the small bowel. Malabsorption.

• Coeliac disease

  Also known as gluten-sensitive enteropathy, an autoimmune condition triggered by the ingestion of gluten found in wheat, barley, and rye, involving immune-mediated damage to the intestinal mucosa
• Genetic predisposition to coeliac disease

  • HLA-DQ2 and HLA-DQ8 play a significant role in susceptibility
• Timing of gluten introduction into the diet

  Considered a risk factor for coeliac disease
• Pathogenesis of coeliac disease

  Gluten-derived peptides, particularly gliadin, resist digestion and cross the epithelial barrier, interact with antigen-presenting cells, activate T cells in the lamina propria, leading to the production of pro-inflammatory cytokines, tissue damage, and antibody formation
• Clinical signs of coeliac disease

  • Villous atrophy, crypt hyperplasia in the small intestine, affecting the proximal small bowel, inflammation of the mucosa of the upper small bowel, malabsorption, symptoms like fatigue, anaemia, abdominal pain, weight loss, diarrhoea, bloating, steatorrhea, mouth ulcers, dermatitis herpetiformis, infertility
• Tropical sprue


  Characterized by chronic diarrhoea, anorexia, abdominal distension, weight loss, and vitamin B12 deficiency, believed to have infective origins and more prevalent in tropical regions
• Pathology of tropical sprue

  • Abnormal jejunal mucosa, partial villous atrophy
• Bacterial overgrowth

  Excessive proliferation of bacteria in the small intestine, commonly Escherichia coli and Bacteroides species, often due to structural abnormalities and altered intestinal motility
• Clinical presentation of bacterial overgrowth

  • Diarrhoea, steatorrhea due to deconjugation and dehydroxylation of bile salts by excess bacteria, complications may include nutritional deficiencies and malabsorption syndromes
• Bile acid malabsorption


  Resulting from various conditions affecting the small intestine, leading to disruption of normal water and electrolyte absorption due to higher concentrations of bile acids reaching the colon
• Causes of chronic diarrhoea

  • Infection
  • Idiopathic causes
  • Post-infective gastroenteritis
  • Post-cholecystectomy syndrome
• Pathogenically, interruption of bile acid reabsorption in the small intestine

  Leads to higher concentrations of bile acids reaching the colon, causing disruption of normal water and electrolyte absorption
• Complications of bile acid malabsorption may include dehydration, electrolyte imbalances, and malnutrition
• Diagnosis of bile acid malabsorption

  Typically involves a SeHCAT scan to assess bile acid absorption
• Management strategies for bile acid malabsorption

  • Medications such as bile acid sequestrants like cholestyramine or colesevelam
• Ileal resection refers to the surgical removal of a portion of the ileum, often associated with conditions such as Crohn’s disease or traumatic injury
• Clinically, bile salt-induced diarrhoea, steatorrhea, gallstone formation, oxaluria, and B12 deficiency may occur following ileal resection
• Diagnosis of complications post-ileal resection

  Can involve a SeHCAT scan
• Management strategies post-ileal resection

  • B12 supplementation and a low-fat diet
• Jejunal resection may lead to gastric hypersecretion with high gastrin levels
• Massive intestinal resection, also known as short bowel syndrome, occurs when a significant portion of the small intestine is surgically removed, leading to malabsorption and diarrhoea
• Shortened small intestine ending at a terminal small bowel stoma presents with sodium and fluid depletion, while shortened small intestine in continuity with colon manifests as diarrhoea and colonic oxalate absorption
• Management strategies for massive intestinal resection

  • Increasing salt intake, restricting hypotonic fluids, administering oral glucose-electrolyte mixtures, a low-fat diet, high carbohydrate intake, and cholestyramine
• Whipple's disease is a rare infectious condition caused by the bacterium Tropheryma whipplei
• Whipple's disease primarily affects middle-aged white males
• Pathogenesis of Whipple's disease

  Involves the invasion and proliferation of Tropheryma whipplei bacteria within the body, leading to chronic infection
• Clinical manifestations of Whipple's disease

  • Joint pain and swelling
  • Unintentional weight loss
  • Gastrointestinal symptoms like diarrhoea or fatty stools
  • Abdominal discomfort
  • Fever
  • Systemic symptoms such as fatigue and malaise
• Diagnosis of Whipple's disease

  Requires a comprehensive approach, including clinical evaluation, imaging studies, endoscopy with biopsy of affected tissues, laboratory tests, and histopathology, particularly identifying foamy macrophages containing PAS-positive material
• Mainstay of treatment for Whipple's disease

  • Long-term antibiotic therapy with trimethoprim-sulfamethoxazole
• Radiation enteritis occurs as a consequence of exposure to ionizing radiation, typically at doses exceeding 40Gy
• Radiation enteritis presents in both acute and chronic forms
• Pathogenesis of radiation enteritis

  Involves muscle fibre atrophy, ulcerative changes due to ischemia, and fibrotic strictures, leading to chronic inflammation and scarring
• Symptoms of radiation enteritis

  • Nausea
  • Vomiting
  • Diarrhoea
  • Abdominal pain
  • Malabsorption
• Complications of radiation enteritis may include bowel obstruction, malabsorption, bacterial overgrowth, and persistent bleeding due to mucosal damage and telangiectases formation
• Diagnosis of radiation enteritis

  Based on the presence of symptoms persisting for 3 months or more following radiation therapy, particularly for the chronic form
• Differential diagnosis for radiation enteritis

  • Inflammatory bowel disease
  • Infectious gastroenteritis
  • Malignancies
• Management strategies for radiation enteritis

  • Hyperbaric oxygen therapy
  • Surgical intervention in cases of obstruction or perforation
• What is the primary trigger for coeliac disease?

  The ingestion of gluten, a protein found in wheat, barley, and rye.
• What are the genetic risk factors associated with coeliac disease?

  Genetic predisposition includes HLA-DQ2 and HLA-DQ8.
• How does gluten contribute to the pathogenesis of coeliac disease?

  Gluten-derived peptides, particularly gliadin, resist digestion and cross the epithelial barrier, leading to immune-mediated damage to the intestinal mucosa.