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Thank you, Susan, that makes absolute sense!  And something to pay close attention to with horses that have rancid smells coming out of their nostrils.  Seems that would be a tell tale sign that fungus / bacteria could be at hand.  I usually check for lots of other things like, bad teeth; sinus infections, and all that stuff!  I have to eat dinner soon so I think I am going to end there!  LOL!  Again, thank you, GREAT information.

On Feb 17, 2008 5:54 PM, Susan E. Garlinghouse, DVM <suendavid@xxxxxxx> wrote:

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.

Heidi>

-- 
D'Arcy L. Demianoff-Thompson
cest.mon.virage@xxxxxxxxx

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