Equine Science Update
Reports from the world of  equine research.
Effect of fasting on gut sounds.
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Listening to the sounds of the gastrointestinal tract is a valuable diagnostic aid in horses with  colic. It is  used by clinicians to assess gut motility.

Two types of sound can be heard. Localised contractions of the bowel produce sounds associated with mixing of the gut contents. These are relatively quiet sounds, lasting 2-5 seconds, which occur 2-5 times a minute. More prolonged sounds occur less frequently. These represent propulsive movements of the gut as the contents are moved along.

For descriptive purpose the horse’s belly can be divided into four areas, called quadrants. As different parts of the bowel lie underneath each quadrant the sounds heard at each may differ. The best example is the rushing noise of fluid passing from the small intestine through the ileo-caecal  valve, into the caecum. This is loudest in the right upper quadrant.

Increased movement can be heard in some forms of colic. Indeed,  the prospects of recovery are generally better if there is an increase in gut sounds. In spasmodic colic the sounds are often continuous and increased in intensity.

Most other causes of colic result in reduced gut sounds.

Given the importance of gut sounds in assessing gut function, there has been surprisingly little research into the normal variations that occur.

A study carried out at the University of Saskatchewan in Canada looked at the effect of fasting on gastrointestinal sounds. Dr Jonathon M Naylor (now based at the Ross University School of Veterinary Medicine on St Kitts, in the West Indies)  and his colleagues have published a full report of the research in the Journal of Veterinary Internal Medicine.

Using an electronic stethoscope, they recorded samples of gut sounds from each quadrant and the right mid flank, each lasting one minute. Sounds were recorded twice at twelve-hour intervals. The horses were then fasted for 24 or 48 hours. Sound recordings continued at twelve-hour intervals. A further two recordings were made once the horses were allowed access to hay again.

To get an objective assessment they measured the sound intensities.  They found a wide variation in intensity of gut sounds between different horses. This makes it  difficult to assess the significance of gastro-intestinal sounds - especially on a single examination. Serial examinations showed a marked reduction in sound intensity in fasted horses.

The left upper quadrant was the quietest, probably because it lies over the small colon. The right lower quadrant, which lies over the tip of the caecum was least affected by fasting. This may be because it retained some food, which continued to be digested during the period of fasting. There was a rapid increase in sounds during the 12 hours after horses started eating again.

To see if different examiners perceived the sounds differently the researchers  had two clinicians assess the recordings. Neither knew whether the horse was being fed or fasted at the time the recordings were made.

Interestingly, there appeared to be a wide variation in the number of  sounds identified by the two examiners. There was also little agreement between their findings and the objective measurement of sounds. This was despite them having been given example recordings to listen to before assessing the experimental recordings.

For more details see:
The effects of feeding and fasting on gastrointestinal sounds in adult horses.
JM Naylor, KL Poirier, DL Hamilton, PM Dowling.
J Vet Intern Med (2006) 20, 1408 - 1413
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