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.
There are three species of hookworms that afflict dogs. These parasites are most prevalent in areas of high temperature and humidity (such as the southern United States), where conditions are favorable for the rapid development and spread of larvae.
Hookworms are small, thin worms about one-quarter to one-half inch (.6 to 1.3 cm) long. They fasten their mouth parts onto the mucosa of the small intestines and suck blood and tissue fluids from the host. This can result in severe blood loss and malnutrition...
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.