Intestinal Pathology Flashcards
Structure of the small and large intestines
Long coiled tube with large surface area
Folded mucosa
Enterocytes tall and columnar (villi and microvilli)
Functions of the intestine
Digestion, absorption, excretion
Fermentation vat (cecum)
Defense mechanisms of the intestines
GALT
IEL (intestinal enterocytes length)
Microfold cells
IgA
Microbiota
Cecum and colon function
Microbial carb fermentation
Production of volatile fatty acids (horses)
Movement of water and electrolytes across colonic wall (dogs and cats)
Absorption and conservation of electrolytes and water
Atresia
Complete occlusion of the intestinal lumen from anomalous development of the intestinal wall
Lesions from atresia
Mechanical lesions to fetal BVs in gut
Malpositioning: compromised circulation results in vascular accidents and ischemia
Atresia ani
Most common overall defect of the lower GIT
Failure of perforation of the membrane separating the endodermal guts
Anus and rectum affected
What is atresia ani more common in?
Most common calves and pigs
Happens bitches more than males
What is atresia ani associated with?
Congenital anomalies (umbilical hernias, cleft palate, open fontanels, hypospadias, etc)
Atresia coli
Spiral colon and large and small colon
Hereditary
2 blind ends separating GIT
Atresia Intestinalis (ILEI)
Less common (calves)
Prevents normal movement of the gut content and meconium
Causes dilation of prox segment, progressive abdominal distention, dystocia
Persistant Meckel’s diverticulum
Derived from vitelline duct (yolk sac)
Persist in all mammalian species
Near the termination of the ileum
Which structure can Meckel’s diverticulum be confused with?
The cecum
Diverticulum
Blind outpouching of the intestine that communicates with the lumen (all layers of the bowel)
Megacolon
Large fecal filled colon
Congenital (pigs, dogs, cats, overo foals and humans) or acquired
What causes megacolon
Absense of ganglion cells of myenteric or Meissners plexus (anglionosis)
Damage to colonic innervation
What is megacolon secondary to?
Failure of migration of neuroblasts from the neural crest to the colorectal myenteric plexuses
Atresia ani
Megacolon in cats
In manx cats
From broken pelvic bone, abnormal development of the terminal SC, spina bifida, atresia ani
Lethal White foal syndrome (congenital colonic anglionosis)
Affected foals are white and offspring of frame overo
Appear normal @ birth then they don’t pass meconium → develop colic → die in 72 hrs
Nonperistaltic
Intestinal obstructions
Prox. to the obstruction → accum of gas and fluid
Luminal sequestration of water and electrolytes and mucosal edema
Upper bowel obstruction
Vomiting, dehydration, hypokalemia, hypochloremia, metabolic alkalosis
Lower small intestine/ colon obstructions
Less pronounced electrolytes and acid/ base imbalances
Vomiting less severe
Metabolic acidosis
Dehydration/ catabolism of fat
Intestinal obstruction in horses
Ischemia and rupture in the cecum and colon
Distention ↑→ ↓ venous return, mucosa and submucosa congested and distended, pressure necrosis
Linear foreign body
Dogs and cats (cloth and string)
One portion fixed on base of the tongue or impaction @ pylorus
Free end stretched distally because of peristalsis
Chronic linear foreign body
Pleating of the distal gut
Malnutrition, dehydration, peritonitis
Enteroliths
Common in horses (arabian breed)
Ammonium magnesium phosphate (struvite): Collect around a small central nidus (foreign)
In pelvic flexure or transverse colon
What causes enteroliths
Diets high in magnesium and phosphorus
Impaction of cecum and colon (horse)
Occurs mostly where lumen narrows
Pelvic flexure, transverse, small colon
What causes impaction in horses?
Water deprivation, rough hay, poor dentition, sand and cecal rupture
What can cause cecal rupture
Impaction with firm, dehydrated feed or fluid filled
NSAID, anesthesia
Intussusception
Intussusceptum: entrapped
Intussescipiens: segment
In DSH, siamses and burmese less than a year
Idiopathic most common
Irritability/ hypermotililty
What can cause Intussusception
Parasitic infestation, foreign bodies, viral infections, abdominal sx, IBD, alimentary lymphoma
Intussusception pathogenesis
Vascular strangulation → congestion/ edema → ischemia → infarction → gangrene
