Sand Accumulation in the Colon: A Common Cause of Equine Colic

Lately we have seen a number of colic cases caused by sand accumulation in the horse’s intestine.  These cases can show a wide range of symptoms, from mild pain treated easily in the field to severe cases requiring colic surgery or euthanasia.  Many horses live long and healthy lives with some sand in their system.  They move it through appropriately.  However, if sand intake becomes greater than outflow, net sand accumulation occurs and a problem develops.  In rare cases, a horse can accumulate hundreds of pounds of sand in the large colon.  Major sand accumulation leads to a life threatening intestinal crisis.

Horses accumulate sand in their intestine by eating off of sandy ground, or grazing short stubble on sandy soil.  The most important factor is the particular soil particle size at a location.  Fine clay and loam usually do not pose a problem.  It is the larger soil particles and small gravel in sandy soils which are accumulated in the gut.  By eating off of this type of soil over time, small amounts of sand settle and gradually accumulate in the large colon.

Sand causes intestinal pain and damage by a variety of effects.  It likely causes abrasion to the inside lining of the colon, and the sheer weight of it pressing on the gut wall probably causes decreased blood flow to the colon wall.  A large amount of sand may combine with feed in the colon to create an obstruction that blocks movement of feed material in the colon, effectively plugging the horse up.  Blockage and gas distension of the gut causes gut damage in itself, which further reduces function and leads to more distension.  A cycle of damage and dysfunction develops.  Toxins (endotoxins) are taken in from the damaged gut into the circulation, causing body-wide problems like laminitis.  The compromised gut cannot reabsorb water, causing diarrhea.  The colon can further displace or twist, resulting in an immediate life-threatening crisis only solved by rapid surgical intervention.  In the worst case scenario, the colon wall may become so damaged that it ruptures, spilling manure into the abdomen and causing the rapid demise of the horse.  The goals of veterinary treatment of horses with sand accumulation revolve around pain relief and nursing care to support the body systems, and attempts to remove the sand.  Unresponsive or fully obstructed cases may require surgery, which can be very difficult.

Signs

What signs should horse owners look for?  Diarrhea and/or colic are the most common signs.  Horses with sand accumulation can also experience weight loss and fever.  Colic (abdominal pain) can be demonstrated by generalized restlessness and discomfort, lying down, kicking at the belly, pawing, sweating, looking at the side, rolling or any combination of these signs and many others. Diarrhea, the most common and “classic” sign of sand accumulation in the horse, should be considered a medical emergency. Diarrhea resulting from sand accumulation must be differentiated from other causes by a thorough veterinary workup.

Diagnosis

Veterinarians diagnose sand accumulation in a few ways.  A familiar method is listening for sand in the colon with a stethoscope.  Fluid and feed washing over sand sounds like waves washing over sand at the beach.  A helpful diagnostic tool is radiographs (x-ray).  The minerals in sand show up on an x-ray image as characteristically bright.  Unfortunately, for an animal as large as a horse, sufficient penetration of the abdomen requires a very powerful x-ray generator not available in most equine hospitals.

A simple and effective diagnostic tool is the “glove test.”  A handful of fresh manure is collected and placed in a clear plastic glove, plastic bag or jar.  Water is added and thoroughly mixed with the manure and the contents allowed to settle.  If a significant amount of sand settles to the bottom, it is reasonable to assume that there is significant sand in the colon.  As part of any colic work-up a veterinarian should also perform a rectal examination.  He or she might feel a feed impaction in the colon which accompanies sand accumulation.

Prevention

The key to prevention of sand accumulation is not allowing its intake.  Know your soil type.  If your horses live or eat around sandy soils, they are at risk for sand accumulation.  In that case, you should consider purchasing mats or feeders, or constructing a special feeding area to reduce sand ingestion.  It often is not enough to simply feed in a hay bunk because horses pitch much of their hay onto the ground.  Horses known to be exposed to sand should be fed a psyllium product routinely.  Psyllium is thought to bind sand and help transport it out of the colon.  Feeding psyllium is not a substitute for reducing intake.  Prevention of a problem requires a combined approach of both methods.  Likewise, you should always have your veterinarian look at your feeding area, and discuss possible improvements that may decrease sand ingestion.  When it comes to sand, there is no doubt that an ounce of prevention is worth a pound of cure.