Veterinary Medicine

Diseases of the Digestive System

General principles of digestive tract dysfunction Manifestation of digestive tract dysfunction Principles of treatment Diseases of the buccal cavity, pharynx, esophagus, stomach and intestines Diseases of the digestive system in ruminants

General principles of digestive tract dysfunction

Overview

The digestive tract is responsible for ingestion, digestion, absorption, and elimination.

Dysfunction can occur at any point → clinical signs vary depending on location and severity.

Common Causes of Dysfunction
  • Obstruction (foreign bodies, strictures, volvulus).
  • Infection/inflammation (bacterial, viral, parasitic, fungal).
  • Motility disorders (ileus, vagal indigestion).
  • Nutritional/metabolic disorders (ruminal acidosis, vitamin/mineral deficiencies).
  • Toxins (plants, mycotoxins, chemicals).
Pathophysiology
  • Disruption in digestion/absorption → diarrhea, malnutrition, weight loss.
  • Disruption in motility → colic, bloating, constipation.
  • Disruption in barrier function → systemic illness (e.g., septicemia from enteritis).
Discussion Questions
  • How do motility disorders differ from obstructive disorders in their pathogenesis?
  • Why is the digestive tract particularly vulnerable to toxins and infections?


Manifestation of digestive tract dysfunction

Key Clinical Signs
  • Vomiting: mainly associated with stomach/small intestine diseases, systemic toxins.
  • Diarrhea: small bowel vs. large bowel (different patterns).
  • Constipation/obstipation: megacolon, obstruction, dehydration.
  • Bloat (tympany): ruminants, dogs (GDV).
  • Colic/abdominal pain: equine medicine hallmark.
  • Dysphagia (difficulty swallowing): oral/pharyngeal/esophageal disorders.
  • Weight loss: chronic malabsorption or maldigestion.
  • Systemic Manifestations
    • Dehydration: diarrhea, vomiting.
    • Electrolyte imbalances (hypokalemia, acidosis).
    • Septicemia: bacterial translocation across damaged gut.


Principles of treatment

Core Treatment Strategies:

1. Stabilize the patient first

  • Fluid therapy: replace electrolytes, correct acidosis/alkalosis.
  • Pain management: essential in colic, bloat.

2. Identify and remove cause

  • Surgery: obstruction, foreign body, displacement.
  • Antimicrobials: bacterial infections, septicemia.
  • Anthelmintics: parasitic infestations.
  • Diet modification: nutritional causes.

3. Supportive therapy

  • Antiemetics (dogs/cats), anti-diarrheal measures (rare in food animals).
  • Gastroprotectants (omeprazole, sucralfate in small animals/horses).
  • Probiotics, prebiotics.

4. Prevent recurrence

  • Improve nutrition, management, hygiene.
  • Vaccination (e.g., against rotavirus, coronavirus, E. coli in calves).


Diseases of the buccal cavity, pharynx, esophagus, stomach and intestines

1. Buccal Cavity
  • Stomatitis: inflammation from trauma, viruses (FMD, Calicivirus), toxins.
  • Dental disease: malocclusion in rabbits/horses; periodontal disease in dogs.
2. Pharynx & Esophagus
  • Pharyngitis: abscesses, foreign bodies.
  • Megaesophagus: congenital/acquired > regurgitation.
  • Esophageal obstruction (“choke” in horses, cattle).
3. Stomach
  • Gastric dilatation-volvulus (GDV) in dogs: acute, life-threatening.
  • Gastric ulcers: common in pigs, horses (EGUS), dogs.
  • Parasitic gastritis: Ostertagia in cattle, Haemonchus in small ruminants.
4. Intestines
  • Enteritis: viral (parvovirus, rotavirus), bacterial (Salmonella, E. coli).
  • Parasitism: coccidiosis, strongyles.
  • Intestinal obstruction: intussusception, volvulus, foreign bodies.
  • Inflammatory bowel disease (IBD): in dogs/cats.


Diseases of the digestive system in ruminants

Unique Features of Ruminants
  • Complex stomach: rumen, reticulum, omasum, abomasum.
  • Dependence on microbial fermentation.
  • Prone to metabolic and fermentative disorders.
Common Diseases:
  • Bloat (ruminal tympany):
    • Frothy bloat (legume pasture).
    • Free-gas bloat (obstruction, vagal indigestion).
  • Rumen acidosis: from high-grain diets > lactic acid accumulation.
  • Hardware disease (traumatic reticuloperitonitis): ingestion of foreign objects.
  • Displaced abomasum (DA): left or right displacement, often post-calving dairy cows.
  • Parasitic gastroenteritis: Haemonchus, Ostertagia, Trichostrongylus.
  • Johne’s disease (Paratuberculosis): chronic wasting, diarrhea.