Equine Colic

Question 1

Know the anatomy of the equine intestinal tract, including names of the sections of the small and large intestine and the flexure between each section of the large colon.

Answer 1

Stomach
Pyloris
Duodenum
Jejunum (& mesentery)
Ileum

ILEOCECAL JX
Cecum
Right ventral colon (sacculated) - sternal flexure
Left ventral colon (sacculated)
PELVIC FLEXURE
Left dorsal colon - diaphragmatic flexure
Right dorsal colon

Transverse colon
Small colon
Rectum

Question 2

List the sites in the equine GIT where impactions are most likely to occur, and explain why this occurs.

Answer 2

Tend to occur in sacks, bends or bottlenecks of GIT.

Cecum - only two small openings
Ileum - associated with muscular hypertrophy or Bermuda grass hay (?)
Pelvic flexure - tight bend with decrease in size of lumen
Transverse colon - decrease in lumen size
Small colon - does not stretch a lot

Question 3

Define colic, and explain the general pathophysiologic mechanisms that cause colic in horses.

Answer 3

Colic is the manifestation of visceral abdominal pain.

Gas
Impaction/obstruction
Strangulating obstruction
Non-strangulating infarction
Inflammatory disease (ulcers, peritonitis, colitis, etc.)

Question 4

Describe the clinical signs that a horse is experiencing mild, moderate, or severe abdominal pain.

Answer 4

Mild: stretching, pawing, looking at flanks, get up/down or lie in sternal recumbency; normal HR, easy to control with or without meds

Moderate: + intermittent tachycardia; repeated medication often required to control pain

Severe: self-trauma (shoulder, tuber coxae, zygomatic arches) due to severe abdominal pain, persistent tachycardia, pain may be uncontrollable with meds

Question 5

What factors are important to keep track of when working up a colic?

Answer 5

Pain - severity, duration, response to analgesics
Pulse - strength, rate, rhythm (>60 immediately pass stomach tube)
Perfusion - membrane color and refill time, temperature of extremities
Peristalsis - 30-60 seconds in all four quadrants
Palpation per rectum - findings can support decision to pursue medical or surgical tx
Passage of NG tube - presence of reflux usually indicates obstruction or anterior enteritis
Paracentesis - normal lactate <2, TP <2.5, WBC<5000 - CBC check evidence of endotoxemia
PCV, TPP, Lactate - hydration, protein loss, perfusion (high abdominal vs peripheral lactate - likely strangulating lesion)

Question 6

Explain to a client the clinical signs or other indicators that a horse with colic needs to undergo exploratory laparotomy.

Answer 6

Persistent and uncontrollable pain
Positive rectal findings of a potential surgical lesion
Large volumes of nasogastric reflux / distended with gas/fluid
Deterioration of clinical or metabolic parameters
Failure to pass manure for a long period of time

Question 7

Understand the risk factors for colic management - habits, age, feed

Answer 7

Factors that increase risk:
- Arabians
- breeding animals (mares)
- cared for by trainers/managers
- daily turnout w/o water
- high grain content of diet (esp. corn)
- history of previous abdominal surgery
- history of previous colic
- orthopedic/musculoskeletal issues (stall bound)

Factors that may decrease risk:
- regular access to green pasture
- regular anthelmentic treatment
- consistent feed and exercise schedule
- regular dental care
- consistent access to water at an appropriate tempurature

Question 8

List the drugs most commonly used to manage pain in horses, their mechanism of action, possible adverse effects, time to onset, and duration of effect.

Answer 8

Alpha-2 Agonist:
xylazine - rapid relief of severe pain; short duration of effect (20-45 min); bradycardia/bradyarrhythmia, ataxia, decreased GI motility, increased urination
detomidine - rapid onset; long duration of action; same side effects - may mask signs of serious surgical problem for hours

NSAID:
flunixin meglumine - 15-20 minutes to work; GI ulceration, renal papillary necrosis
phenylbutazone - less potent in blocking hemodynamic effects of endotoxin; more potential for GI ulceration and renal papillary necrosis
ketoprofen - least toxic to GIT and kidneys

Selective COX2 inhibitor:
ferocoxib - less toxic to GIT, no difference in renal toxicity

Opioid:
butorphanol - minimal sedation, minimal cardiovascular depression; for rapid sedation and analgesia, administer lower doses in combination with xylazine; high doses can cause ataxia and excitatory effects

Anticholinergic:
Buscopan - several minutes after IV admin, HR elevated for 30 min and not reliable indicator of pain