Metabolic Bone Disease

Metabolic bone diseases are characterized by a thinning and loss of bony mass, predisposing the bone to fractures and growth deformities. The most common metabolic bone disease seen in dogs and cats is hyperparathyroidism. This condition is characterized by a calcium deficiency within the body that leads to abnormal bone growth and bone resorption as the body tries to correct the low calcium levels in the bloodstream. Hyperparathyroidism can result from feeding pets all-meat diets (which are naturally low in calcium), or it can result secondary to kidney disease.

Dogs and cats afflicted with metabolic bone diseases exhibit lameness, weakness, bone and joint deformities, and spontaneous fractures. Diagnosis is based on radiographic X-ray findings and on blood calcium measurements. Treatment for nutritionally related bone disease obviously involves changes in the diet and calcium supplementation. Treatment for kidney-related hyperparathyroidism is geared toward counteracting the kidney disease itself.

Another type of metabolic bone disease that can affect cats is called hypervitaminosis A. This condition is seen in those cats fed an exclusive diet of liver, which contain high levels of vitamin A. Musculoskeletal changes seen in cats experiencing chronic vitamin A toxicity include bony deformities, outgrowths, and fusion involving the vertebral column, especially in the region of the neck, and bony fusion of the joints of the limbs, resulting in pain and immobility.

A history of an all-liver diet, combined with clinical signs and radiographic analysis of the spine and limbs, can reveal conclusive evidence of hypervitaminosis A. If detected early in its development, this condition can often be reversed by switching the cat to a balanced diet. However, in advanced cases, the bony changes that occur are usually permanent, and anti-inflammatory medications are usually required for the remaining life of the cat to help ease the pain associated with the disease.

Mucopolysaccharidosis (Cats)

Mucopolysaccharidosis is an inherited disorder that has been documented in Siamese cats. It results from an enzyme deficiency that allows polysaccharide carbohydrates to accumulate within the cells of the body.

The skeletal system is particularly affected, with stricken cats suffering from bony spurs on the vertebrae, arthritis and abnormal formation of the joints, and a generalized osteoporosis, or thinning of the bones themselves. These cats also have a characteristic “flattening” of the face, resulting from a widening of the facial structure, and, at an early age, can suffer from opacities or cloudiness involving the corneas of both eyes.

Diagnosis of mucopolysaccharidosis is made by physical examination, blood tests, and radiographic X rays of the skeletal system. A special test that detects mucopolysaccharides in the urine can also be employed in diagnosing this disorder. Unfortunately, because of the inherited nature of this disease, there is no known treatment. Future generations should be protected by neutering those pets affected to prevent passage of the trait.

Myositis and Myopathies

Myositis is inflammation of muscle tissue that results in pain, weakness, and muscle atrophy (shrinking). Dogs and cats suffering from severe bouts of myositis are reluctant to move and can actually appear as if they are paralyzed as a result of the inflammatory effects on the muscles. Myositis can be caused by a number of different disease entities, including toxoplasmosis, leptospirosis, bacterial infections (abscesses), low blood potassium (see text below), and autoimmune disease. One special type of myositis, called masticatory myositis, affects the facial muscles of affected dogs, causing atrophy and the inability to chew normally. This autoimmune disease is seen most frequently in German shepherds.

Myositis is diagnosed using clinical signs and blood tests designed to detect increased levels in muscle enzymes within the blood. In especially elusive cases, biopsy samples taken from suspected muscle tissue can help veterinarians obtain a definitive diagnosis.

Treatment for myositis is aimed at the underlying cause. If infections are to blame, appropriate antimicrobial or antiparasitic therapy will help relieve the myositis. Anti-inflammatory medications can also be used to relieve the pain and discomfort associated with the inflammation until the underlying cause is treated.

Autoimmune myositis, such as masticatory myositis, is treated with high levels of glucocorticosteroids (such as prednisolone) in an effort to suppress the immune response causing the inflammation in the first place. The prognosis for complete recovery with autoimmune myositis is poor, yet with medications, the signs associated with the disorder can be kept under control.

The term myopathy refers to abnormal anatomy and/or function of skeletal muscle tissue within the body. Most myopathies in dogs are inherited. Chow chows, golden retrievers, and Irish terriers are examples of breeds that can suffer from inherited myopathies. Dogs suffering from myopathies exhibit abnormal postures, stiff gaits, and generalized shrinking or atrophy of the muscles. Because of the inherited nature of these diseases, the onset of clinical signs usually occurs within a year of age. Unfortunately, there is no effective treatment to stop the progression of these myopathies.

Hypokalemic Myopathy (Potassium Depletion) in Cats

As an electrolyte, potassium serves a variety of functions within the body, including maintaining proper fluid volume and pH. Potassium is also necessary for normal muscle contraction. Many illnesses in cats can also produce deficiencies in this electrolyte, or hypokalemia, within their bodies. This is especially true for those cats suffering from kidney disease, liver disease, or diabetes mellitus. Actual signs of hypokalemia can include weight loss, loss of appetite, constipation (due to poor motility of the muscles lining the gastrointestinal tract), muscle weakness, muscle pain, and incoordination. As the condition progresses and respiratory muscles become affected, breathing difficulties might be noted. In severe cases, death from respiratory paralysis could result.

Diagnosis of hypokalemia in a sick cat is based on a history, clinical signs, and measurements of blood potassium levels. If hypokalemia is diagnosed, treatment consists of intravenous injections of a potassium supplement to correct the immediate deficit, followed by oral supplementation as long as deemed necessary.

Prognosis for recovery is good if treatment begins early on.

Hernias

A hernia results from a tear or defect in a muscular wall, allowing the contents contained behind the wall to protrude through the opening in the muscle. In dogs, the four most prevalent types of hernias include umbilical hernias, inguinal hernias, perineal hernias, and diaphragmatic hernias. In cats, diaphragmatic hernias are the types most commonly seen.

Umbilical hernias occur on the midline of the dog’s stomach at the location of the umbilicus, or the belly button. These usually result from trauma to the muscle wall in this area that occurs when the bitch severs the umbilical cord after birth. Umbilical hernias pose no real health problems, since fatty tissue is usually the only item that ever protrudes through the opening. These hernias can be sutured and repaired at the time of other elective surgeries.

Inguinal hernias occur in the inguinal region of the abdomen, or that region where the abdominal musculature meets that of the hind legs. They are seen as birth defects or secondary to trauma. These hernias are more serious than umbilical hernias, since the herniated material often includes intestines. As a result, normal digestive processes can be disrupted. Treatment involves surgical replacement of the herniated material back inside the abdomen and suturing the defective muscle.

Perineal hernias result from a weakening of the musculature in the region located beneath the tail on either side of the anus. Seen primarily in older male dogs that have not been neutered, perineal hernias can involve portions of the colon and cause impactions and elimination problems if not surgically corrected. Because the hormone testosterone seems to play a role in the development of these hernias, neutering these dogs is also recommended to prevent a recurrence.

By far the most serious type of hernia is the diaphragmatic hernia. The diaphragm is the thick wall of muscle that separates the thorax or chest cavity from the abdominal contents. Tears or ruptures occurring in this band of muscle, resulting either from inherited defects or from traumatic incidents, can allow liver, intestines, and/or other abdominal contents to herniate into the chest cavity. When this happens, the pressure applied to the crowded lungs and heart results in, among other things, breathing difficulties, weakness, and/or gastrointestinal disturbances.

Definitive diagnosis of a diaphragmatic hernia can be made by coupling history, clinical signs, and a physical examination with radiographic X-ray findings. Surgical repair of the torn diaphragm will alleviate the signs and usually result in a complete recovery.

Vestibular Disease

The vestibular system is a specialized portion of the nervous system found within the inner ear, brain, and spinal cord. Its duty is to maintain a state of equilibrium and balance. By communicating with the nerves supplying the eyes, limbs, and trunk, the body is able to coordinate the position and activity of these regions with movements of the head.

Peripheral vestibular dysfunction (PVD) is a disease that affects the nerves of the vestibular apparatus in the ears. PVD is characterized by a sudden onset of incoordination and loss of balance, which is often accompanied by a head tilt, involuntary twitching of the eyeballs, and in many cases, vomiting. The causes of this disorder can include trauma to the ears, skull infections, and tumors involving the middle or inner ear. Diagnosis of PVD is achieved using clinical signs and various laboratory tests to rule out other potential causes of the symptoms. Radiographs of the skull may be helpful in the detection of any masses or infections that may involve the inner portions of the ears. Treatment, of course, depends on the underlying cause and usually includes high doses of corticosteroid medications designed to reduce inflammation involving the vestibular apparatus.

Vestibular ataxia syndrome is seen in kittens born of queens stricken with feline parvovirus during pregnancy. Owners often are alerted to a problem when these kittens seem to have trouble in attempting to walk. The condition will not improve as these kittens mature, nor will it usually worsen.

Congenital vestibular syndrome is seen in Siamese and Burmese cats, with signs appearing anywhere from 2 to 4 weeks of age. Many of the Siamese cats affected are deaf as well. The prognosis for Siamese

cats with congenital vestibular syndrome is good, with clinical signs usually abating by the time the cat is 6 months of age. In Burmese cats, however, the prognosis is not as good, and the poor quality of life for most of these individuals will usually warrant euthanasia.

Date: 2015-12-11; view: 915