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In our last post, we discussed (mainly) non-surgical types of large intestinal colic.  However, as we all know, sometimes colic goes beyond what we can treat in the field and referral for surgery is necessary.  Typically, these result from the colon moving (or displacing) into a place that it shouldn't be.   That being said, some of these can be treated medically, however not always successfully.  Since we've already gone over the anatomy of the large colon, (See Large Intestinal Colic: Part One) let's jump right into what might have happened if your horse's bowel becomes blocked.
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Right Dorsal Displacement: The left colon is quite mobile and likes to get stuck in places.  In a right dorsal displacement (RDD), the left colon slides around to the right side of the abdomen and gets stuck between the cecum and the body wall.  The pelvic flexure (the U-shaped area at the top of the picture) moves from the back end of the abdomen (near the rectum) to end up near the diaphragm.  This is all kinds of crazy!  The large intestine becomes partially occluded and gas distended.  In practice, we can see this occur in conjunction with a pelvic flexure impaction.  Generally speaking, the blood supply remains intact so the bowel remains healthy.  We can sometimes treat these with fluids and withholding feed, but often times surgery is required.  At surgery, the colon just needs to be decompressed and repositioned into the appropriate anatomic location.  As long as nothing more serious is going on, these horses recover quite well. 

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Left Dorsal Displacement:  Again, the left half of the colon goes for a walk-about.  This time, it slides up along the left body wall and gets hung up between the spleen and the kidney.  Why?  Well, there's structure there called the nephrosplenic ligament - merely a tissue attachment between the spleen and the kidney.  (That's also why the other name for this type of displacement is a "nephrosplenic entrapment".)   The problem is that this ligament can act like a hammock for the large colon.  And we all know how hard it is to get out of a hammock!  Feed material may still be able to pass through initially, but gas buildup and the excess weight on the spleen pushes that organ out of position as well.  This can be quite uncomfortable, as you can imagine.  Medical therapy with phenylephrine (given slowly intravenously) can sometimes to shrink the spleen allowing the colon to "fall" off the nephrosplenic ligament (usually assisted with trotting or trailering the horse), however is not usually successful.  Attempts are sometimes made to anesthetize and "roll" a horse to try to dislodge the spleen as well, but this is difficult for many reasons.  Surgery is sometimes required (we estimate 50% of these colics require surgery), and again aims at merely emptying the colon and putting it back where it belongs. 

Colon Torsion or Volvulus: (Above) This is one of the scariest types of large intestinal colic.  Imagine a line drawn along the length of a horse through the chest and out the back end.  Then we take the large colon and twist it around this line, spinning it on its axis.  That is a volvulus, and while they commonly rotate clockwise, it can go in either direction.  If the colon rotates >360 degrees, blood supply will be cut off and significant injury to the bowel occurs.  This generally results in a poor prognosis and requires euthanasia.  However, if it is less than 270 degrees rotated, the colon is usually ok and just needs to be twisted back around that rod.  This is more common in broodmares post-foaling as there is a large amount of space left in the abdominal cavity after the foal is born.  Surgery is required to correct a volvulus. 
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Cecal Impaction:  In the previous post, we mentioned pelvic flexure impaction.  While this is probably the most common area for an impaction, it is not the only area where an impaction can occur.  The cecum is another structure that can become impacted, and medical treatment can be difficult.  Initially, horses with cecal impactions have intermittent colic which can become more severe if it is prolonged in course.  Surgery is often recommended to removed the impaction, especially if medical therapy is not successful.  Prognosis if surgery is performed is fair, as success rates are about 70%.  The success rate rises to 80% if these cases are able to be treated medically.    

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Enteroliths:  An enterolith is a concretion that forms in the GI tract.  The term broken down is entero (GI tract) and -lith (stone).  It is very uncommon to see this in the Northeast where we are, but can be seen in areas such as the southwest and Florida.  It's unclear what causes these to form, it often occurs in horses with higher mineral concentrations.  Feeding of alfalfa hay has been attributed to this higher mineral concentration. 

The problem with enteroliths is that they can grow large enough to plug up the GI tract.  Not only that, but they can abrade the lining of the intestine.  Imagine if you had a boulder rolling around in your gut!  Horses will typically show recurring colic signs, but can become extremely painful when the lumen of the intestine becomes blocked.  Surgery is required to remove these, but prognosis tends to be quite good.

The colon is a complex structure in horses and as such causes many problems.  Some of these can be treated easily on the farm, but sometimes they require referral for further care or surgery.  The choice on whether or not to do surgery should be made prior to any problems occurring, as it can be an emotionally and financially draining endeavor.  That being said, depending on the issue, large intestinal colic surgery does usually carry a good prognosis. 
 
 
Previously, we have discussed small intestinal colic and gastric ulcers.  However, when discussing colic, we have to determine if it is small intestinal in origin or large intestinal. 
Below is a brief list of problems associated with the large colon.  Typically, these are non-surgical and can be resolved with some medical management.  That's not ALWAYS the case, but for the most part it is.  (Part 2 will focus on more severe types of large intestinal colic.)


 
 
Colic is a scary word to horse owners and veterinarians.  However, some types of colic are much worse than other types.  While 90% of colic cases resolve with minimal treatment on the farm, some require more intensive care.  One such type of more serious colic  is small intestinal strangulation, which is an obstruction of the blood supply and the lumen (the inside of the tube, where food passes through) of the small intestine. 
GI Anatomy1. Stomach 2. Small intestine 3. Cecum
The horse's gastrointestinal system is quite lengthy - it spans approximately 120 feet, and the majority (70-80 feet) of that is small intestine.  Furthermore, it's mostly floating freely in the abdomen, with minimal attachments to the body wall and surrounding organs.  This conformation gives lots of opportunities for something to go wrong, whether that's a twist, or some other way that the intestine ends up in the wrong spot. 
 
The small intestine (or SI, for short)  is the same in horses as it is in dogs, cats or humans.  It's made up of 3 segments - the duodenum, the jejunum and the ileum.  The duodenum is the first section, just after it leaves the stomach and for about the next 12-16 inches (that's it - so, not much goes wrong with the duodenum!)  The jejunum makes up the bulk of the small intestine, and the ileum comprises the last foot or so before it enters the cecum.  There are minor variations in these structures, but we don't have to worry about them here.  All this SI is suspended within the abdomen by a sheet of connective tissue called "mesentery".  (If you laid a garden hose straight across a towel, then picked the towel up at all 4 corners it would create the same effect.)  The mesentery brings blood supply to the intestines. 


 
 
The equine digestive tract is always a concern for horse owners - and veterinarians!  Colic can be caused by many different things, and one possibility is EGUS - Equine Gastric Ulcer Syndrome.  Gastric ulcers are actually quite common in horses.  There are a variety of reasons for this, but have no fear!  While they are common, they are rarely life-threatening and can be cured with appropriate treatment.
Picturewww.egus.org
First, let's start with an anatomy overview.  The equine stomach is divided into two sections - the non-glandular (or squamous) section, and the glandular area.  The line dividing these areas is known as the "margo plicatus".  Stomach acid is secreted by the glandular area.  We typically see ulcers along the margo plicatus on the squamous side of the stomach, but we can also see ulcers throughout the non-glandular and glandular regions.  Oh yeah, and just to be clear, gastric ulcers are erosions in the normal lining of the stomach.  Pretty simple so far, right?


 
 
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The eye is a very delicate organ, and horses specifically have eyes which are in a very precarious position.  In order to allow for a nearly 360 degree view around them, horse eyes are placed well on the outsides of their heads.  This anatomic location combined with a horse's normal "flight" response makes eye injuries quite common.  One of the most common things we see are corneal ulcers. 


 
 
Every so often it happens – your horse just doesn’t seem right and you need to call the vet.  When you do, it’s important to have as much information as possible so your vet can get a good picture of what’s going on.  Here are five of the most common questions we ask horse owners – know these, and you’re one step ahead of the game!


 
 
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With the warm fall we've been enjoying, it may be hard to remember that winter is just around the corner.  Soon enough, however, we'll be battling snow and frozen ground as we take care of our equine companions.  It's important to put some thought and time into preparing your horse and your property before winter sneaks up on us completely.  We've outlined a few things to keep in mind to help this transition time be as seamless as possible. 


 
 
Recently, mosquitoes infected with EEE (Eastern Equine Encephalomyelitis virus) were found in Voluntown, CT.  Not only that, but there have been 2 confirmed cases of EEE positive horses in Massachusetts.  While it would be nice to hide from it, the fact is that it is in our backyard.  But what do we really know about it? 
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USDA map Oct. 2012
EEE is mainly found in the US east of the Mississippi river, and throughout areas of Central and South America.  The virus persists in “reservoirs” – wild animals that carry the disease such as bats, rodents, and birds.  A vector (such as a mosquito) becomes infected when it feeds on one of these animals.  Most often, EEE is maintained through a transmission cycle between birds and mosquitoes.  The mosquito then carries the virus for life and can transmit it through its saliva.  If a horse happens to be the source of the next blood meal, then they can become infected and quickly begin to show signs. 

Once infected, it takes approximately 5-15 days for signs to show up.  These signs can be very mild such as a fever and depression; or severe including blindness, stumbling, seizures or death.  Any neurologic signs could be indicative of EEE, however other diseases such as rabies must be considered as well, and a diagnosis should be confirmed via testing.  Unfortunately, a diagnosis is often obtained post-mortem.  If EEE is suspected, the state veterinarian must be contacted and the disease needs to be reported.


 
 
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When it comes to the equine eye, we often discuss common diseases such as corneal ulcers, conjunctivitis or uveitis.  We do treat these conditions quite a bit, however there are some  serious uncommon diseases that we do have to think about when considering an inflamed eye.  One of these diseases is glaucoma, which can be set off by any of the above listed issues, or by another underlying problem.


 
 
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This time of year, it's good to be a horse vet.  The weather is delightful, and we get to see lots of healthy patients for routine things - vaccines, dentistry, reproductive work.  Foals have been arriving for a few months now, and you have to admit, there is not much cuter than a newborn foal.  Cuteness aside, however, deciding to breed horses is a big decision, and not one to be taken lightly.  If this is something you have been considering for your mare or stallion, read on.


 

Twin Pines Equine Veterinary Services, LLP. All rights reserved.
Twin Pines Equine Veterinary Services, LLP