Intestinal Pathology

Question 1

Structure of the small and large intestines

Answer 1

Long coiled tube with large surface area
Folded mucosa
Enterocytes tall and columnar (villi and microvilli)

Question 2

Functions of the intestine

Answer 2

Digestion, absorption, excretion
Fermentation vat (cecum)

Question 3

Defense mechanisms of the intestines

Answer 3

GALT
IEL (intestinal enterocytes length)
Microfold cells
IgA
Microbiota

Question 4

Cecum and colon function

Answer 4

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

Question 5

Atresia

Answer 5

Complete occlusion of the intestinal lumen from anomalous development of the intestinal wall

Question 6

Lesions from atresia

Answer 6

Mechanical lesions to fetal BVs in gut
Malpositioning: compromised circulation results in vascular accidents and ischemia

Question 7

Atresia ani

Answer 7

Most common overall defect of the lower GIT
Failure of perforation of the membrane separating the endodermal guts
Anus and rectum affected

Question 8

What is atresia ani more common in?

Answer 8

Most common calves and pigs
Happens bitches more than males

Question 9

What is atresia ani associated with?

Answer 9

Congenital anomalies (umbilical hernias, cleft palate, open fontanels, hypospadias, etc)

Question 10

Atresia coli

Answer 10

Spiral colon and large and small colon
Hereditary
2 blind ends separating GIT

Question 11

Atresia Intestinalis (ILEI)

Answer 11

Less common (calves)
Prevents normal movement of the gut content and meconium
Causes dilation of prox segment, progressive abdominal distention, dystocia

Question 12

Persistant Meckel’s diverticulum

Answer 12

Derived from vitelline duct (yolk sac)
Persist in all mammalian species
Near the termination of the ileum

Question 13

Which structure can Meckel’s diverticulum be confused with?

Answer 13

The cecum

Question 14

Diverticulum

Answer 14

Blind outpouching of the intestine that communicates with the lumen (all layers of the bowel)

Question 15

Megacolon

Answer 15

Large fecal filled colon
Congenital (pigs, dogs, cats, overo foals and humans) or acquired

Question 16

What causes megacolon

Answer 16

Absense of ganglion cells of myenteric or Meissners plexus (anglionosis)
Damage to colonic innervation

Question 17

What is megacolon secondary to?

Answer 17

Failure of migration of neuroblasts from the neural crest to the colorectal myenteric plexuses
Atresia ani

Question 18

Megacolon in cats

Answer 18

In manx cats
From broken pelvic bone, abnormal development of the terminal SC, spina bifida, atresia ani

Question 19

Lethal White foal syndrome (congenital colonic anglionosis)

Answer 19

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

Question 20

Intestinal obstructions

Answer 20

Prox. to the obstruction → accum of gas and fluid
Luminal sequestration of water and electrolytes and mucosal edema

Question 21

Upper bowel obstruction

Answer 21

Vomiting, dehydration, hypokalemia, hypochloremia, metabolic alkalosis

Question 22

Lower small intestine/ colon obstructions

Answer 22

Less pronounced electrolytes and acid/ base imbalances
Vomiting less severe
Metabolic acidosis
Dehydration/ catabolism of fat

Question 23

Intestinal obstruction in horses

Answer 23

Ischemia and rupture in the cecum and colon
Distention ↑→ ↓ venous return, mucosa and submucosa congested and distended, pressure necrosis

Question 24

Linear foreign body

Answer 24

Dogs and cats (cloth and string)
One portion fixed on base of the tongue or impaction @ pylorus
Free end stretched distally because of peristalsis

Question 25

Chronic linear foreign body

Answer 25

Pleating of the distal gut
Malnutrition, dehydration, peritonitis

Question 26

Enteroliths

Answer 26

Common in horses (arabian breed)
Ammonium magnesium phosphate (struvite): Collect around a small central nidus (foreign)
In pelvic flexure or transverse colon

Question 27

What causes enteroliths

Answer 27

Diets high in magnesium and phosphorus

Question 28

Impaction of cecum and colon (horse)

Answer 28

Occurs mostly where lumen narrows
Pelvic flexure, transverse, small colon

Question 29

What causes impaction in horses?

Answer 29

Water deprivation, rough hay, poor dentition, sand and cecal rupture

Question 30

What can cause cecal rupture

Answer 30

Impaction with firm, dehydrated feed or fluid filled
NSAID, anesthesia

Question 31

Intussusception

Answer 31

Intussusceptum: entrapped
Intussescipiens: segment
In DSH, siamses and burmese less than a year
Idiopathic most common
Irritability/ hypermotililty

Question 32

What can cause Intussusception

Answer 32

Parasitic infestation, foreign bodies, viral infections, abdominal sx, IBD, alimentary lymphoma

Question 33

Intussusception pathogenesis

Answer 33

Vascular strangulation → congestion/ edema → ischemia → infarction → gangrene