Equine Colic

Gas and impaction colics

The majority (80%) of colics are gas or impaction colics. They look very similar. They are treated very similarly and respond well to field treatment. Both have a good prognosis as long as the causative factors are managed.

Impaction colics

Impactions may develop for 3 main reasons:

  • Foodstuffs are not easily digestible. Ex: Poor mastication due to speedy eating, poor dentition, or poor quality feeds
  • The gut isn’t able to digest things well due to a change in motility or change in flora activity. Ex: atropine treatment for eye issues, pain or illness, exercise changes, feed changes
  • The ingesta doesn’t slide well due anatomical and physiological challenges (there are lots of these) or because the ingesta is dry, hard or sticky. Ex: dehydration, enterolith formation

Anatomical and physiological challenges

  • Friesians have abnormal gastric motility
  • Ileal break reflex slows emptying
  • Pelvic flexure creates a hairpin turn with narrowing
  • Cecum is blind-ended
  • Small colon is narrowed
  • Absorption of water from the small colon

 

Gas colics

Gas or tympanic colics develop when:

  • Diet changes result increased gas production by the microbial flora. Ex: diets high in corn (fermentable), sudden feed changes
  • Motility changes prevent farting and/or prevent more fermentation due to delayed transit times. Ex: pain, atropine, electrolyte abnormalities (endurance racing, hot weather).

Diagnostics

  • Both gas and impaction colics lead to mild to moderate colic signs and decreased manure production. Heart rate is generally only mildly elevated (40-60bpm). Horses can become mildly dehydrated. Horses may look bloated with gas colics. Reflux is not generally seen.
  • Differentiating between gas and impaction colics requires rectal palpation and even that may be inconclusive. However, both can be managed similarly so the challenge is only in differentiating field vs referral colics.

Treatment
1. Rehydrate/overhydrate

  • Give fluids orally via nasogastric tube and/or iv. Oral is more effective! Generally give 4-8L (or 1 to 2 gal) total to 1000# horse.
  • Gastric distension stimulates colonic activity through the gastrocolic reflex
  • If you have difficulty passing the nasogastric tube into stomach due to esophageal sphincter tone, add 25-30 ml lidocaine

2. Provide pain relief

  • Pain stimulates the flight response and shuts down motility
  • NSAIDs such as flunixin meglumine are commonly used (remember – don’t give banamine im due to the risk of clostridial myositis)
  • Buscopan can be given once to help with intestinal spasms. This helps gas colics more than it helps impaction colics. Note : it will cause an elevated heart rate for 30 minutes!

3. Stimulate motility

  • Walk horses to stimulate GI motility
  • Grazing may also help (grass, not hay)

4. Prevent worsening

  • Remove hay and grain (grazing, grass okay) until the horse poops

5. Consider laxatives –

  • Magnesium sulfate (Epsom salts) are the primary laxative used to treat feed impactions.  Horses should not be given more then 1g/kg/day (about 1 pound per day in 1000lb horse).  This is administered orally via the NG tube in 4-6L of water.  CAUTION: Horses with gastric ulcers can become very colicky after administration (as you can imagine, OUCH!) and indicates referral for gastroscopy.
  • Dioctyl Sodium Sulfosuccinate (DSS) is a laxative but rarely used in the USA due to the potential of inducing a severe colitis.
  • For a feed impaction, mineral oil can be used to help determine transit time but is really ineffective at breaking up the impaction. Mineral oil can help with gas colics.
  • If sand : psyllium 0.5 g/kg PO BID or 1g/kg PO SID combined with 2L mineral oil
    Psyllium and/or mineral oil can be given in place of oral water via nasogastric tube
    Or could give ½ gallon water and ½ gallon oil

6. Monitor response to treatment

  • Signs of pain, defection, rectal palpation if indicated and safe
  • Most impaction and gas colic will resolve with just one visit. Refer if severe, not manageable, or not responding within 12-24h! That typically means they are in the other 20% of colic types

Resources

 

License

Icon for the Creative Commons Attribution-NonCommercial 4.0 International License

Large Animal Surgery - Supplemental Notes by Erin Malone, DVM, PhD; Elaine Norton, DVM PhD; Erica Dobbs, DVM; and Ashley Ezzo, DVM is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.