Introduction

• Poor absorption of nutrients from small intestine.
• Cause: altered intestinal mucosal or lymphatic function.
• Signs: chronic diarrhea, weight loss, vomiting, polyphagia or anorexia.
• Diagnosis: history, physical examination, laboratory tests, abdominal ultrasound, intestinal histopathology.
• Treatment: dependent on underlying cause.
• Prognosis: can be guarded.

Pathogenesis

Etiology

• Mucosal damage often due to inflammatory or neoplastic response.
• Multiple causes of inflammation including:
  • Parasitic.
  • Bacterial.
  • Dietary.
  • Hypersensitivity
  • Infectious agents.
  • Most cases idiopathic.
• Intestinal lymphangiectasia (IL), resulting in dilated and ruptured lacteals and loss of protein rich lymph into the intestinal lumen.
• Multiple cases of IL including:
  • Primary or idiopathic.
  • Inflammatory bowel disease Inflammatory bowel disease: overview.
  • Intestinal neoplasia Small intestine: neoplasia Large intestine: neoplasia.
  • Right-sided heart failure.
  • Obstruction in lymphatic circulation arising from a mass, granuloma, etc.

Specific

• Inflammatory bowel disease Inflammatory bowel disease: overview :
  • Lymphocytic/plasmacytic enteritis Enteritis: lymphocytic plasmacytic.
  • Eosinophilic enteritis Enteritis: eosinophilic.

• Villus atrophy:
  • Gluten-sensitive enteropathy Gluten-sensitive enteropathy.
  • Idiopathic.
  • Severe acute infectious enteropathies, eg Parvovirus Canine parvovirus Parvovirus disease associated with CPV-1.

• Antibiotic-responsive diarrhea (ARD) Antibiotic-responsive diarrhea (ARD) :
  • Exocrine pancreatic insufficiency Exocrine pancreatic insufficiency.
  • Idiopathic.
  • Secondary to inflammatory bowel disease (IBD).
• Neoplasia:
  • Lymphosarcoma Lymphoma.
  • Adenocarcinoma Adenoma / adenocarcinoma.

• Chronic infectious enteropathies:
  • Giardiasis Giardiasis.
  • Salmonellosis Salmonellosis.
  • Campylobacter spp Campylobacter jejuni.
  • Cryptosporidia spp Cryptosporidium spp.
• Lymphangiectasia Diseases of the lymphatic vessels:
  • See above for various causes.

Pathophysiology

• Reduced nutrient absorption due to:
  • Villous atrophy Intestine: villus atrophy → decreased surface area → decreased absorptive capacity.
  • Mucosal damage → loss of mucosal integrity → increased intestinal permeability.
  • Mucosal damage → loss of brush border enzymes → decreased digestion and absorption. 
  • Infiltration of lamina propria with inflammatory or neoplastic cells → reduced absorption and altered motility.
  • Lymphangiectasia → malabsorption of lipoproteins and fats due to defective lacteal function.

Timecourse

• Weeks to months.

Diagnosis

Treatment

Outcomes