Meadow ~ What I take away from reading the two articles below is that the entire mechanism of Bloat is still not fully understood. One author states that the overwhelming majority of cases are caused by an unusual felt-like mat of hair (very different from the normal hair in the system from grooming), another also presents evidence of carpet fibers, gastric ulcers, and scar tissue being factors. Our extremely rabbit-savvy vet is of the opinion that there is at least some gut slowdown (GI Stasis) prior to complete obstruction.
From ~ http://www.ohare.org/images/harelines/v13n2.pdf ~ “Harelines” ~ the newsletter of the Buckeye HRS ~ Spring/Summer 2009 ~ Volume 13 Number 2 ~ by Dr Barbara Oglesbee, DVM ~ Capital Veterinary Referral & Emergency Center ~ Columbus, OH
WHAT IS THE MOST COMMON CAUSE OF OBSTRUCTION? The answer may surprise you and causes a lot of confusion over the term “hairball.”
More than 90% of intestinal obstructions are caused by a mat of hair.
It is important to realize that this mat of hair is NOT the normal hair that is swallowed by the rabbit every day when he grooms himself.
The mat of hair causing the obstruction is very, very dense and resembles a little block of felt.
It is usually no bigger than a large almond.
It is not really known exactly where these mats of hair come from. Some believe that they are swallowed whole, as hair mats off the rabbit during grooming. Most likely, however, they are formed in the cecum.
Hair that is swallowed in the normal process of grooming goes into the cecum, where it gets compacted into a small, dense mat.
Occasionally this mat of hair gets passed with the rest of the cecotropes and is eaten by the rabbit. As you know, cecotropes are swallowed whole without chewing.
This almond-sized mat now goes into the stomach where it causes no problem, but when it gets passed into the intestine it gets stuck.
The usual spot is 2-3 inches from the stomach, where the small intestine naturally gets narrower.
Other, less common causes of obstruction include cloth, plastic or tumors.
From ~ L. Seeman, MSN (January 2004) at http://www.bunnylu.org/bloat.html ~
Current literature from the UK reveals bloat is caused by a blockage or obstruction in the GI tract that may be due to a foreign body (carpet) or tricobezoar (hairball).
During postmortem exams on rabbits whose cause of death was GI Stasis or bloat, Dr. Paul Flecknell found an obstruction at the exit to the stomach (pylorus or duodenal flexure).
The tissue at this site was often dead (necrotic).
He also found instances in which the lining of the stomach had eroded with bleeding present. While not specifically documented, this creates the possibility that ulcers and/or scar tissue could be precursors to bloat.
A study by Hinton (1980) showed 7% of all rabbits necropsied had gastric ulcers.
Considering the nature of rabbits as prey animals, it makes sense that rabbits could and do develop stress ulcers.
It is known that gastric ulceration in rabbits can develop from pain and fear due to catecholamine (epinephrine) release, and also with reduced gut motility, such as repeated episodes of stasis.