Checking the Vitals: Abdominal Sounds


Anatomy of the Gut

Veterinarians often joke that the abdomen of the horse was designed by a committee: it is complex and the obvious source of our leading killer, colic, which literally means pain with an abdominal origin. The horse has a unique abdominal anatomy, with the gut being within a space also shared by the liver, kidneys, and spleen. The reproductive organs also are present in females, with pregnancy being almost like the ever-enlarging living tumor. In males, the reproductive organs originate within the abdomen, then descend.

If we follow an oat kernel from the time of ingestion to digestion, it is quite a trip with strategic digestive processes. Anatomically, after the esophagus empties into the stomach, food and water begin transport through the abdominal viscera. The stomach is relatively small (2-4 gallons) and empties into the small intestine. Compare that to the 40-50-gallon vat called the rumen in the cow. If that oat kernel runs into a problem in the stomach of a cow it can be churned, fermented, and regurgitated for more chewing (cud). The horse is a species that does not regurgitate or vomit, thus the kernel is either trapped there or slowly exits into the duodenum, travels on to the jejunum and then the ileum, a trip of about 70 feet in length for the cumulative small intestine.

The small intestine ends with the muscular ileum that empties into the large colon and cecum, collectively called the "hindgut." Foals become hindgut fermenters at about three to four months of age. The cecum in the horse serves as a blind but large fermentation sac located on the right side of the abdomen. The large colon also originates there at the junction of the ileo-cecal-colic valve, a favorite site for tapeworms. The cecum and colon are significant fermentation processing plants, with the large colon starting on the right, circling forward toward the diaphragm then going along on the left, folding upward and back on itself, before again going forward then passing back over to the right side to end with the junction to the small colon.

The large colon is a major fluid resorption area and the small colon is where the fecal balls are formed. The large colon is about 35 feet long with a large diameter, and it is followed by the small colon and rectum, which make up about 12 feet in length. Obviously, the journey for that oat kernel was significant--it traveled more than 150 feet in a few hours or less--and is completed out the rectum and anus usually as a digested hull of the original oat kernel.

Listening to Your Horse's Abdominal Sounds

Having an appreciation for the anatomy of the bowels gives the veterinarian an approach to detecting the location of a problem during the physical examination. Listening to both sides of the abdomen both high and low can be done by placing your ear against the abdomen, but this is not nearly as precise or safe as using a stethoscope. The sounds to be heard are a mixture of gurgling, gaslike growls, fluid as tinkling sounds, and occasionally "roars" as grumbles in the normal horse (similar to us apologizing to our companions for that occasional loud abdominal sonic storm). These would be normal sounds that the veterinarian refers to as either peristaltic or "borborigmus," and they reflect normal bowel activity.

In most cases silence is the signal of something abnormal. Since no special time clock is within the abdomen for sounds, it means listening to both sides of the abdomen for at least a minute each. Hearing the presence of bowel sounds should reassure you that things are still moving along as expected. Silence might sometimes be a sign of excessive gas or an impending diarrhea. Faint tinkling sounds might signify infection or a significant colic lesion. Searching for sounds or the lack thereof is important and your veterinarian will appreciate as much information as you can obtain from observing your horse and listening to his abdomen whenever the clinical signs are subtle.

When indicators of abdominal discomfort are not subtle or they are obvious: sweating, rolling horse that you can't keep up ... call the veterinarian immediately. You don't need to concern yourself with listening for bowel sounds when the horse is reacting so violently. Sick horses with intestinal compromise should always be examined by a veterinarian, since even subtle problems can become life-threatening. The veterinarian can provide a more complete examination process, including passing a stomach tube and/or performing a rectal exam. The veterinarian might also use ancillary diagnostics such as ultrasound evaluation, and he or she might obtain laboratory samples, usually consisting of blood work and rarely an abdominal fluid tap.

Owners become guardians of their horses by paying attention to problems their horses might present. Not eating, slow eating, excessive gas production, changes in the character of the feces, weight loss, or chronic colic are signs needing interpretation. The stethoscope allows the listener a cursory appreciation of abdominal abnormalities, as he or she notes changes that can be heard, or not heard. The additional "vitals" information relayed to your veterinarian will be the temperature and the heart and respiratory rates, along with an evaluation of the mucous membranes. A quick appreciation of the vital signs with abdominal sounds is usually a window providing effective communications for both you and your veterinarian regarding a horse's immediate health status.

Reprinted with the permission of the Kentucky Horse Council.

About the Author

Doug Byars, DVM, Dipl. ACVIM



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