Digestive, Hormone, and Autoimmune Ills; Poisonings

By Dennis Blodgett.

There are many causes of digestive problems, and in general the causes are similar for dogs and cats. However, prevalence of the various digestive problems differs for each species.

The most common signs of digestive problems are vomiting and diarrhea. Other less common clinical signs of digestive problems include constipation, bloat, abdominal pain, excessive salivation, difficult swallowing, and lack of appetite. Some of the most common causes of vomiting and diarrhea in dogs and cats will be discussed.

Vomiting is produced by stimulation of the vomiting center in the brain stem. Vomiting is not always due to irritation of the gastrointestinal tract, however. Heart, liver, and genitourinary tract irritations, motion sickness, kidney failure, various infections, and particular drugs or toxins may also produce vomiting.

One of the more common causes of vomiting from gastrointestinal irritation is a dietary problem. This may result from a sudden change in diet or from ingesting foreign materials. Foreign materials (such as dirt, plants, garbage, and poisons) are more commonly ingested by dogs, especially puppies, than by cats.

Internal parasites also may induce vomiting but mainly produce diarrhea. Some internal parasites found in dogs and cats are roundworms, hookworms, tapeworms, whipworms, flagellates, and coccidia. Roundworms and tapeworms are the most likely of these parasites to produce vomiting.

Both bacterial and viral infections of the gastrointestinal tract may induce vomiting. Some of the most common viral infections which cause vomiting and diarrhea in the dog and cat are canine distemper, panleukopenia (feline distemper), and canine parvovirus. Canine parvovirus has been especially devastating in the last few years.

Digestive tract obstructions are another common source of vomiting. Foreign bodies are one of the most common obstructions. They may be either in the stomach or intestines. Dogs tend to swallow bones, toys, cloth, metallic objects, or stones. Cats are more likely to ingest hair, thread, string, or cloth.

Intussusceptions, when one part of the intestinal tract collapses or telescopes into an adjoining part of the tract, are another common obstruction. They often are associated with vomiting over an extended period of time.

An additional cause of vomiting in dogs and cats is inflammation of the pancreas. This condition usually occurs in obese, middle-aged dogs. Exact cause of the pancreatic inflammation varies, but often an unbalanced diet is involved. Diarrhea also is present in about half the cases.

Diarrhea. Causes of diarrhea in dogs and cats are as extensive as those of vomiting. Although diarrhea often accompanies vomiting, diarrhea may be present by itself.

Diarrhea results from problems in the small or large intestines. Vomiting or weight loss in conjunction with diarrhea is more likely due to a problem in the small intestine than in the large intestine.

Small intestine diarrhea often has markedly increased volume, undigested food, and color variations. Large intestine diarrhea has normal to increased volume, mucus commonly, and usually no undigested food or color variations.

An addition to the causes of diarrhea mentioned under vomiting is pancreatic exocrine insufficiency. The pancreas is unable to produce adequate amounts of the enzymes, lipase and amylase, for the small intestine. This results in an inability to digest fats and starches, which produces a voluminous fatty diarrhea.

Pancreatic exocrine insufficiency affects dogs more commonly than cats. The condition can be inherited or the result of a long-term pancreatic inflammation.

Other causes of diarrhea include overeating, bile deficiency, intestinal tract tumors, lymphatic disorders, and various drugs.

Hormone Disorders

Hypothyroidism is a condition in which inadequate amounts of circulating thyroid hormone are produced. The condition may occur with or without goiter (enlarged visible gland in the neck).

The most frequent hypothyroidism in small animals is without a goiter. The thyroid glands shrink in size. Although the syndrome affects both dogs and cats, it most often is diagnosed in larger breeds of dogs 2 to 5 years old.

Decreased thyroid hormone output results in a decreased metabolic rate. Often the animal has a cold body temperature and seeks out warm places to lie down. The hair frequently is coarse and thinning and the skin may be thickened and pigmented.

Increased body weight often is seen due to the decreased metabolic rate. Mental activity may be decreased or more sluggish. Once a diagnosis of acquired primary hypothyroidism has been made, the animal is given thyroid hormone medication for the rest of its life.

Excessive parathyroid hormone (PTH) occurs in primary disease of the parathyroid glands, accompanying longstanding kidney failure, and due to nutritional imbalances of calcium and phosphorus or not enough vitamin D3.

Excessive PTH can be found in both dogs and cats. When due to kidney failure there is decreased blood calcium and decreased intestinal absorption of calcium. When due to nutrition it often is the result of feeding all meat diets high in phosphorus and low in calcium. Clinical signs with both forms of excess PTH are related to excessive loss of calcium from the bones. Animals may be lame, paralyzed, or have rubbery jaws. Calcium is supplemented in the diet for both forms.

Eclampsia (Puerperal Tetany) is due to reduced calcium in the blood of dogs or cats which recently have had litters. It results from an inability of the body to immediately compensate for the loss of calcium in the milk.

Most frequently eclampsia is seen in small breeds of dogs and only occasionally in the cat. Usually the syndrome appears 1 to 3 weeks after birth of the litter when milk production is at its peak.

Clinical signs associated with eclampsia include nervousness, trembling, staggering, muscle tremors, and seizures. Intravenous injection of a calcium solution results in rapid improvement of the animal.

Diabetes mellitus is most often due to decreased insulin output by the pancreas. Insulin is the hormone responsible for the utilization of sugar in the body. A deficiency of insulin results in increased blood glucose concentrations.

This endocrine disorder affects both dogs and cats. Affected animals lose high amounts of sugar in the urine, which carries excessive amounts of water with it. An increase in the loss of water is accompanied by increased water consumption. Because of the high loss of sugar calories in the urine, animals often eat more but nevertheless lose weight. Further complications may result in vomiting, dehydration, and coma.

Insulin is injected daily to treat animals, just as it is for human diabetics.

Autoimmune Ills

The body has an immune system which defends it against foreign substances such as bacteria and viruses. An important factor in the immune response is the production of antibodies against these foreign substances.

Usually antibodies are formed only against foreign substances and not against cells normally found in body tissues. However, on rare occasions an individual produces antibodies against cells in its own body (that is, autoantibodies). This is an immune response against oneself or an autoimmune response.

Autoimmune responses occur in various species of animals and in humans for a variety of reasons which are not totally understood. A few of the most common autoimmune diseases in the dog and cat will be discussed.