Pathophysiology of Intestinal Obstruction in the Horse (Mudge) Flashcards
(38 cards)
Take me from the esophagus to anus – what is the order of the equine digestive tract?
- Esophagus
- Stomach (cranial left side)
- Duodenum (right -> left)
- Jejunum (70ft long)
- Ileum
- Cecum (right side)
- Right ventral colon
- Sternal flexure
- Left ventral colon
- Pelvic flexure
- Left dorsal colon
- Diaphragmatic flexure
- Right dorsal colon
- Transverse colon
- Descending (small) colon
- Rectum
- Anus
What is colic?
- Refers to abdominal pain
- Usually involves the disorders of the gastrointestinal system
How many feet of small intestine does the average adult horse have?
70ft
Classification of Obstruction:
Includes simple and strangulating
- Luminal obstruction causes accumulation of solid, liquid, and gas
- Acute onset of clinical signs
Complete
Classification of Obstruction:
Usually simple obstruction
- Luminal obstruction causes accumulation of solid +/- liquid
- Often liquids and gas ‘squeak’ past the obstruction
- Slower onset of signs of an obstruction than complete
Incomplete
Simple Obstructions:
- Stricture
- Intraluminal
- Intraluminal Obstruction
- Impaction (feed or sand)
- Enterolith
- Mass (neoplasia or FB)
- Extraluminal
Mechanical
Simple Obstructions:
- Visceral displacements
Malposition
- “large colon”
Simple Obstructions:
- Ileus
- Inflammation (enteritis)
Functional
- not a true obstruction
Simple intestinal obstruction can lead to increased intraluminal pressure. What are 3 secondary intestinal effects that can occur after simple obstruction?
- Decreased perfusion to seromuscular and mucosal layers
- Increased microvascular permeability
- Mesothelial cell loss, neutrophil infiltration, edema – can lead to adhesion formation
- Can also lead to pressure necrosis, especially with a solid obstruction (enterolith)
Definition:
an abnormal union of membranous surfaces due to inflammation or injury.
Adhesion
List simple obstructions in the small intestine:
- Impaction
- Ileal impaction
- Ascarids
- Foreign body (rare)
- Mass/ neoplasia (not very common)
- Adhesions
- Intussusception
- initially non-strangulating
- Functional
- ileus
- enteritis
List simple obstructions – Large Intestinal Impaction/Obstruction:
- Feed impaction
- Pelvic Flexure
- Right dorsal colon/ Transverse colon
- Cecum (less common)
- Type I = feed
- Type II = functional/fluid
- Small colon
- Often inflammatory
- Narrowing of the intestinal lumen
List other simple obstructions – Large Intestinal Impaction/Obstruction:
- Sand Impaction
- RDC
- Enterolith
- RDC
- Transverse & Small Colon
- Fecalith
- Small Colon - Minis and foals
- Phytotrichobezoars (eating hair)
List the Risk Factors for simple Obstructions:
- Ileal Impaction
- Jejunal Impaction
- Ileocecal, cecoceal, cecocolic intussusception
- Large colon impactions (stress, diet, dentition, dehydration)
- Large colon displacement (recent dietary changes, recent parturition, large breed)
- Enterolithiasis (alfalfa hay, breed (Arabian, Miniature), lack of pasture access, geography)
What are enteroliths made of?
(enteroliths are made of magnesium, ammonium, phosphate)
Struvite
Which of the following is a simple obstruction?
a. Transverse colon impaction
b. Peritonitis
c. Inguinal hernia
d. Large colon volvulus
a. Transverse colon impaction
What are 4 common causes of non-strangulating (simple) obstruction of the large colon in the horse?
- Large colon Impaction
- Small colon Impaction
- Enterolithiasis
- Large colon Displacement
- Right dorsal and left dorsal displacement could be counted separately
Definition:
are intestinal stones that form within the colon and can obstruct the intestine, resulting in colic
Enteroliths
List Strangulating obstructions in the Small Intestine:
- Mesenteric Volvulus
- Constricting bands
- Pedunculated lipoma
- Herniation
- Entrapment
- Intussusception = can become strangulated
List Stangulating Obstruction in Large Intestine:
- Large Colon Volvulus
- Small Colon Constriction
- Pedunculated lipoma
Definition:
occurs when a loop of intestine twists around itself and the mesentery that supports it, causing bowel obstruction
Volvulus
From the time of twisting, how long does it take for it to become chronic?
6 hours
List the Secondary Effects of Strangulating Obstruction:
- Hypovolemic Shock
- SIRS/Endotoxemia (Septic Shock)
- Obstructive Shock
- Pain
What contributes to shock?
- Third spacing of fluids within the obstructed lumen
- Sweating and increased insensible losses
- Reduced/absent volume intake
- Endotoxemia can develop with intestinal stasis
