Intestinal obstruction, especially duodenal obstruction, can cause sudden complete anorexia and death within 12-24 hours i.e. the rabbit was eating at tea-time but dead the following morning. The cause of obstruction is usually a pellet of compressed fur that has the appearance of a hard faecal pellet. Some rabbits will eat their hard faeces or those of their companion. If the pellet was from a moulting rabbit, it will be composed of compressed fur. Large pellets can lodge in the small intestine.A video of the typical post-mortem findings in a rabbit that died from intestinal obstruction can be seen here.
The cardiac sphincter of rabbits is strong so they cannot vomit or burp and if the small intestine is obstructed, there is no exit for fluid and gas so the stomach rapidly distends.It can rupture to release gastric contents into the abdomen. In other cases, it is the small intestine that ruptures because the small intestine proximal to the site of the obstruction can also become tympanitic. Occasionally it will burst.
In rabbits that have been dead for more than an hour, it can be difficult to be certain that a perforation of the stomach or gut was ante-mortem change. The presence of a pellet of hair confirms the diagnosis. If the stomach has ruptured, the pellet of hair may still be in the intestine. If the intestine has ruptured, the pellet may be found in the abdominal cavity.
Not all rabbits with an intestinal obstruction will have died from a perforated stomach or small intestine. They may die from shock, acute renal failure or from toxaemia from an area of devitalised necrotic intestine. In rabbits, stress readily causes temporary vasoconstriction of the renal arterioles and reduces blood flow to the kidneys. Rabbits that were in shock when they died may have obviously pale kidneys.