[RC] hydration via rectum - Susan E. Garlinghouse, DVM
Hi all,
A few people emailed me privately and asked about this, so
thought I’d jump in briefly to comment on it. Sorry if it’s
already been adequately explained elsewhere.
Yes, it is physiologically possible for horses (and other
species) to absorb water through the rectal/colon wall that has been introduced
retrograde up the rectum (read “up the horse’s arse”).
A large part of the function of the large bowel is to absorb water, and the
bowel doesn’t care whether the water is originating from upstream or downstream.
HOWEVER, it is a damned dangerous thing to try to do this,
and even very experienced vets don’t do it lightheartedly. Even in
a fully hydrated horse, the equine rectal wall is a lot easier to perforate
than are other species (like a cow). Punch through all the layers of the
bowel wall, and you’ve got fecal material spilling into an open abdomen,
pending septic shock and Dead Horse Walking. The more dehydrated a
horse gets, the more friable those tissues become, and the easier it is to tear
rectal walls. In a very dehydrated horse, those walls are like tissue
paper. Thus if you’re trying to rehydrate a horse in real trouble
(or even one that is only minimally dehydrated), this is a very risky way to
introduce fluid back into the system, and a distant third choice from fluids
via IV catheter or via nasogastric tube (the latter also has its drawbacks, but
less so than rectal administration). The tricky part of
administering fluids via rectum is that you have so many fun ways of damaging
the horse---either the hand/arm introducing the hose, the hose itself (even a
small, soft one), or even the weight of the water being introduced is enough to
perforate compromised rectal tissue. It can be done, but in a compromised
horse, you have to do it so slowly and carefully, that your time is better
spent administering fluids by other routes.
I was once called to a barn to treat a horse that had been
acting colicky, but wasn’t critical---from the symptoms, it had sounded
pretty routine, and no, it wasn’t an endurance horse, just a horse whose
water had accidentally been turned off about twelve hours previously in fairly
cool weather. When I got there, the owner said someone else at the barn
had told them “let me show you how to save a $300 vet bill”.
They put a hose up the horse’s arse and turned on the water—not even
full blast, just a trickle. The rectal walls ruptured, and the horse
ended up being euthanized for an abdomen full of horsesh*t and septic shock.
Yes, they did indeed save a considerable vet bill, but got to write the check
to the deadstock haulers instead.
I appreciate riders attempting to find extra ways to keep
their horses hydrated at a ride, but this is NOT the way to do it.
Hope this clarifies the issue. Sorry if it’s
redundant.
