Rectal tears are unfortunately an inherent risk associated
with rectal examination of horses. While rectal tears can be a
complication, the amount of knowledge gained by performing
a rectal exam outweighs the risk when proper precautions are
taken. Lots of information can be gained by examining a colicky
horse by rectal palpation. For example—assessing prognosis and
determining if surgery is necessary or not—these are major decisions for the horse. Also with breeding soundness examinations,
rectal examination can provide accurate information on where a
mare is in her estrous cycle and when is the best time to breed.
The risk of causing a rectal tear should not be the reason to skip
performing a rectal examination as these risks can be minimized
for the examination.
How rectal tears occur:
There are a variety of causes with the most common being
iatrogenic trauma to the rectum. This means during a rectal examination, as the rectum contracts around the vet’s hand or arm
or rectal probe, the rectum tears. It can also, although much less
commonly, be caused by penetration of the rectal wall by fingertips.
Other causes include parturition (delivering a foal) or dystocia (malpositioning of the foal during birth) leading to tears,
breeding mishaps (such as a stallion accidentally penetrating the
mare’s rectum during breeding) and trauma.
Which horses are more at risk:
Some risk factors have been identified with rectal tears.
Breeds such as Arabian horses and miniature horses have been
shown at higher risk due to restless behavior and small rectum size.
Colicky horses are also at a greater risk of tearing due to repeated
rectal exams. Colicky horses are also typically dehydrated which
can lead to a dry and fragile rectal lining (mucosa). You may hear
of age and sex predilection being risk factors however they vary in
the literature and are not consistent between studies as to whether
younger or older horses are more “at risk”.
Types of rectal tears:
You may hear rectal tears being classified on a 1-4 grade
scale. This grading is based on which layer of the rectum is torn.
It is important to classify a rectal tear to determine what course
of treatment is best for the horse. The grades are broken down by
which layer (or layers) of the rectum is (are) torn (see figure 1).
Measures your veterinarian takes to minimize risk:
For horses that are straining around the vet’s arm, drugs
such as Buscopan® or xylazine can be administered to reduce
the straining and thereby reduce the risk for tearing. Buscopan is
an antispasmodic that relaxes the smooth muscle in the rectum
therefore relaxing the rectum of a straining horse. A caudal epidural (similar to epidurals women can have during childbirth)
can also be used to decrease straining. Using ample lubrication
and adequate restraint (sedation or a twitch) while performing
a rectal exam also decreases the chances of causing a rectal tear.
How your vet will manage a rectal tear if it happens:
A rectal tear is usually detected when blood is present on
the arm or sleeve of the examiner. This is a serious incident and
should be dealt with promptly. With adequate initial management
and prompt referral to a surgical clinic, horses have a 79% survival
rate. The rectum should be evacuated of feces and the tear will
be classified based on the grade it is (what layers of the rectum
are torn) by palpation. Then the rectum should be packed with
a moistened cotton roll covered by a stockinette and sprayed in
Iodine to reduce the fecal contamination into the tear. Packing
the rectum is intended to deliver a better surgical candidate to a
referral center for further treatment. Starting the horse on broad
spectrum antibiotics to combat any fecal contamination as well
as an anti-inflammatory is also beneficial. Mineral oil can also be
administered through a nasogastric tube to soften and lubricate
the feces for a laxative effect. Horses will then need to be referred
for further evaluation and surgical correction of the tear.
Prognosis for horses with rectal tears depends on the size,
grade of the tear, time between occurrence and treatment, as well
as prompt initial first aid by your veterinarian. In various studies
looking at the outcome for horses with rectal tears, the prognosis
for each grade varies however it is fairly unanimous that grade 4
tears (which go through all layers of the rectum) typically have a
poor prognosis and can be rapidly fatal.
Rectal tears can happen, but that should not deter a rectal
exam from being performed when it is a valuable diagnostic tool.
There is so much information your vet can gain by rectal palpa-tionwhich can sway decisions one way or another when deciding
the best course of action for a horse. With proper and adequate
restraint, the risk of tearing is very low.
Rectal Tears in Horses Happen
What You Need to Know About Them
By Ava Nowak, DVM Student (Class of 2015)
Edited by Dr. Tim Lescun, BVSc, MS, Dipl. ACVS,
Purdue Large Animal Surgery
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