Gastrointestinal diseases

• Anatomy of GI Tract

  • Upper GI
  • Mouth, esophagus, stomach, duodenum
  • Lower GI
  • Jejunum, ileum, cecum, colon
• Parts and Lining of Stomach

  • Sections of stomach
  • ○ Lower esophageal sphincter, cardia, fundus, pylorus, pyloric sphincter
• Parts and Lining of Stomach

  • 4 layers
  • Lining- mucosa
  • Submucosa
  • Muscularis externa
  • Serosa
• Parts of Small Intestine

  • Duodenum
  • 1st section of small intestine- attached to stomach
  • Proximal duodenum entrance point for pancreatic and common bile ducts
  • Neutralizes stomach acid, mixes enzymes to help break down chyme, absorbs nutrients
• Parts of Small Intestine

  • Jejunum
  • 2nd section of small intestine
  • Absorbs sugars, fatty acids, and amino acids
• Parts of Small Intestine

  • Ileum
  • 3rd section of small intestine
  • absorbs bile acids, fluid, and vitamin B-12
• Parts of Small Intestine

  • Cecum
  • Small pouch extrusion between ileum and colon (ileocecal junction)
  • Stores food material where bacteria are able to break down the cellulose
• Lining of Small Intestine

  • Villi: folds of intestinal mucosa and submucosa
  • Microvilli: finger-like projections on villi and source of nutrient absorption
• Lining of Small Intestine

  • Crypts: a gland found in between villi in the intestinal epithelium
  • Produces stem cells to help repair damage epithelium
• Lining of Small Intestine

  • Contains B and T lymphocytes and glands that produce alkaline secretions
  • Cells produce mucus and antimicrobial lysozymes
• Parts of Colon

  • Ascending, transverse, and descending
  • removes water and some nutrients and electrolytes from partially digested food
  • Excretes feces out of body
• Bacterial Diarrhea

  • E. coli
  • Gram-negative, facultative anaerobic, rod-shaped, coliform bacteria
  • Found as normal flora of GI, but not all types
• Bacterial Diarrhea

  • Salmonella
  • facultative anaerobic, Gram-negative, rod-shaped, flagellated bacteria
• Bacterial Diarrhea

  • Clostridium
  • Gram-positive, most of them are strictly anaerobic, non-sulfate reducing, rod shaped bacteria able to form endospores
• Bacterial Diarrhea

  • Camplyobacter
  • Gram-negative, microaerophilic, spiral-shaped, “S”-shaped, or curved, rod-shaped bacteria
  • Can be found as normal flora
• E. coli 0157:H7

  • Binds to intestinal lining → begins producing Shiga toxin → disrupts protein synthesis in epithelial cells → cell death → sloughing of lining
• Salmonella

  • Adheres and invades epithelial cells in mucosa and submucosa→ attach specifically to endocytic cells in Peyer’s patches to create inflammation → secretes endotoxin & exotoxin → forces cells to create ethanolamine (“food” source) → replicates in macrophages → inflammation impairs absorption
• Clostridium

  • Produces a spore once reaches small or large intestine → spore produces enterotoxin (& others) → damages intestinal lining cells → causes inflammation and sloughing of tissue
• Campylobacter

  • Attaches to enterocytes on mucosal lining → releases enterotoxin & cytotoxin → causes IgA production → increases inflammation and permeability of interstitial fluids into lumen
• Bacterial Diarrhea- Clinical Signs

  • Acute diarrhea
  • Some cases will be persistent over extended period of time
  • May or may not have blood
  • Blood most common with salmonella
• Bacterial Diarrhea- Clinical Signs

  • Mild-severe lethargy
  • Anorexia (not eating)
  • Painful abdomen
  • +/- fever (hyperthermia)
  • +/- vomiting
• Bacterial Diarrhea- Physical exam

  • BAR-QAR
  • Lethargic
  • Painful on abdominal palpation
  • vomiting/retching in the exam room
  • Defecation in the exam room
  • +/- delayed capillary refill time and exaggerated skin turgor
• How do we Diagnose (Bacterial Diarrhea)?

  • Rule out other causes of diarrhea
  • Fecal float to rule out parasites
  • Rads to rule out foreign body or abdominal mass
  • CBC/chem to rule out hepatic, renal, metabolic, and endocrine diseases
• How do we Diagnose (Bacterial Diarrhea)?

  • Rule out other causes of diarrhea
  • Fecal float to rule out parasites
  • Rads to rule out foreign body or abdominal mass
  • CBC/chem to rule out hepatic, renal, metabolic, and endocrine diseases
• How do we Diagnose (Bacterial Diarrhea)?

  • Fecal smear
  • Smear small amount on a slide, heat fix, and stain with crystal violet or methylene blue
  • Examine under microscope
• How do we Diagnose (Bacterial Diarrhea)?

  • GI profile
  • PCR panel of most common bacteria
  • Bacterial cultures (rarely used)
• Bacterial Diarrhea- Treatment

  • Antibiotics +/- SQ fluids depending on dehydration
  • Hospitalization very rare unless significant damage
• Bacterial Diarrhea- Treatment

  • Types:
  • Erythromycin: macrolide antibiotic, bacteriostatic
  • Good against aerobic and anaerobic bacteria
  • Give BID-TID
• Bacterial Diarrhea- Treatment

  • Sulfa-/Trimethoprim: potentiated sulfonamide antimicrobial/antiparasitic, bactericidal if combined
  • Good against aerobic and anaerobic bacteria
  • Given SID
• Bacterial Diarrhea- Treatment

  • Enrofloxacin: fluoroquinolone, bactericidal
  • Not good against anaerobic bacteria
  • Give SID
• Bacterial Diarrhea- Treatment

  • Metronidazole: bactericidal, antibiotic/antiparasitic
  • Works against anaerobic bacteria
  • Generally given BID
• Irritable Bowel Syndrome/Disease (IBS/IBD)

  • Severe inflammatory response of the submucosal lining in small and large intestine
  • Idiopathic, chronic food allergies / Intolerance, bacterial or parasitic infection
  • Causes loss of ability for absorption
• Irritable Bowel Syndrome/Disease (IBS/IBD)

  • Lymphocytic- plasmacytic enteritis most common
  • Lymphocytes infiltrate into submucosa → damages mucosa → increases permeability of loss of interstitial fluid
• Irritable Bowel Syndrome/Disease (IBS/IBD)

  • More common in cats than dogs
• Irritable bowel syndrome - Clinical signs

  • Chronic intermittent vomiting +/- diarrhea
  • Lethargy
  • Weight loss, especially if chronic issue
• Irritable Bowel Syndrome/Disease (IBS/IBD)-Clinical signs

  • Polyuria/Polydipsia (PU/PD)
  • Stomach noises (borborygmus)
  • Halitosis and flatulence
  • Older animals are more prone
• Irritable Bowel Syndrome/Disease (IBS/IBD)- Physical Exam

  • BAR-QAR
  • +/- lethargy in the room
  • bloating/ mild ascites build-up palpable
  • +/- “ropey” intestines on palpation
  • Poor haircoat
• Irritable Bowel Syndrome/Disease (IBS/IBD)- Diagnostics

  • CBC/chem
  • Often will see hypoproteinemia (low protein), hypocalcemia (low Ca2+), neutrophilia
• IBS - Diagnostics

  • Fecal float/smear and rads to rule out other diseases
• Irritable Bowel Syndrome/Disease (IBS/IBD)- Diagnostics

  • Ultrasound
  • If owner is against invasive tests, sometimes can see thickening of intestinal wall on ultrasound - not conclusive