[RC] guttural pouch erosion - Susan E. Garlinghouse, DVM
No, this is an entirely different thing, it has nothing to do
with the GI tract. The guttural pouches are an outpouching of the
auditory Eustachian tubes leading to the tympanic membranes (ear drums), so
they’re located behind the nasal sinuses and a bit above and forward of where
the oral and nasal cavities intersect at the larynx. The eustachian tubes
are what you blow air through when you ‘pop’ your ears at changing
altitudes, they’re what allow you to equalize air pressure and avoid
damage to the membranes. The enlargement in horses was kind of a mystery
for a long time, it only occurs in a couple of species to any significant
extent, including horses, rhinos, tapirs and hyrax. How’s that for
an eclectic mix? They thought the guttural pouches were related to
communication, hearing, things like that, but didn’t really know for sure.
A few years ago, they figured out that they’re an evolutionary mechanism
for heat loss during exercise. Horses generate a phenomenal amount of
heat during exercise and too much heat to the brain will obviously cause
significant problems. So by circulating arterial blood past the air
moving through the guttural pouches, the horse can drop the blood temp about
2-3 degrees by the time it leaves the guttural pouches, and thus protect the
brain from reaching a critical hyperthermia. It’s a good trick.
So it’s a pretty slick mechanism for regulating
temperature (and obviously, the horse has lots of other thermoregulatory
mechanisms as well), but it’s kind of a double-edged sword. The
blood traveling at such a shallow depth past the guttural pouches also makes
that blood supply susceptible to damage. It’s not uncommon for a
fungal infection to set up housekeeping in the guttural pouches (it’s
called guttural pouch mycosis), and the fungus causes erosion and damage to the
walls of the pouches, including the carotid artery. If the fungal erosion
causes enough damage to the arterial wall, it can give way entirely and because
the carotid is at such high pressure and receives such a large amount of the
cardiac output from the heart, it can cause catastrophic bleeding.
Does that make sense?
Susan Garlinghouse, DVM
From: D'Arcy
Demianoff-Thompson [mailto:cest.mon.virage@xxxxxxxxx] Sent: Sunday, February 17, 2008 5:29 PM To: heidi@xxxxxxxxxxxxxxx Cc: suendavid@xxxxxxx; Linda Winkel; ridecamp@xxxxxxxxxxxxx Subject: Re: [RC] EIPH bleeder???
Oh, Heidi, I am soo sorry to hear about your mare.
Maybe Sue can answer this question about the erosion of the gutteral
pouch. Is this caused by stomach ulcers. Or are we talking the same
thing with a scientific name?
<, and otherwise the picture of health. Came out one morning and found
her dead, bled out through the nose, and it was an erosion in a gutteral
pouch... So yes, ditto what Susan said--get the horse scoped, and see if
you can find out where the blood is coming from.
