Any problem that interferes with the passage of intestinal contents through
the GI tract results in a blocked bowel. The most common cause is a
gastrointestinal foreign body. The second most common cause is
intussusception-a situation in which the bowel telescopes in upon itself, like
a sock pulled inside out. Most cases of intussusception occur at the cecum,
where the small bowel joins the colon. As the small bowel inverts into the
cecum and colon, the lead point travels a considerable distance, dragging the
small intestine after it. Intussusceptions generally
occur in puppies and young dogs.
Other causes of intestinal obstruction are tumors and strictures, adhesions
following abdominal surgery, and navel and groin hernias that trap loops of
bowel in the hernia sac. In young puppies, heavy infestations of roundworms may obstruct the bowel.
Inflammatory bowel disease (IBD) occurs when a dog’s stomach and/or intestine becomes home to an unusually high number of inflammatory cells. These cells cause changes in the lining of the digestive tract, which inhibit the normal absorption and passage of food.
It is important to note that although some of the symptoms may be similar, IBD is not the same as irritable bowel syndrome, which is caused by psychological stress rather than a physiological abnormality.
An intestinal obstruction can be partial or complete. Partial obstructions
cause intermittent vomiting and/or diarrhea, which tend to occur
over several weeks. Complete obstructions produce sudden abdominal pain and
vomiting that continues without relief. When the blockage is in the upper small
bowel, the vomiting may be projectile. Blockages in the lower GI tract cause
abdominal distension and the vomiting of brown, fecal-smelling material. Dogs
with complete obstruction pass no stool or gas.
Intestinal strangulation occurs when the obstruction interferes with the
blood supply to the bowel. Within hours the bowel becomes gangrenous. The dog’s
condition deteriorates rapidly (see Peritonitis).
The diagnosis of intestinal obstruction is made by abdominal X-rays or
ultrasound showing distended, gas-filled loops of bowel.
Treatment: Obstructions require immediate veterinary attention. Surgical
exploration and relief of the blockage is necessary. Gangrenous bowel is
resected back to viable bowel, and intestinal continuity is restored with
end-to-end suturing of the bowel.
Gastrointestinal Foreign Bodies
Dogs have been known to swallow bones, toys, sticks, stones, pins, needles,
wood splinters, cloth, rubber balls, rawhide, leather, string, peach pits, and
other objects. With string, one end often knots up while the other gets caught
in food. Tension on the string then causes it to cut through the wall of the
bowel. Swallowing pennies will not usually cause an obstruction, but can lead
to zinc toxicity as the metal leaches out of the coins. Batteries can also
cause toxicity when swallowed.