Chihuahua Health

LIVER SHUNTS

This much-discussed disorder is most commonly the result of improper fetal development of the circulatory system. To thoroughly understand liver shunts, it is important to have an understanding of the development of blood vessels in the fetus. The fetus, through the placenta, umbilical vein and artery, is connected to the mother's circulatory system (bloodstream). Therefore, the liquid portion of the blood of the fetus can move into the mother's bloodstream, but the cells cannot. The mother's liver then performs the important liver functions, such as eliminating wastes, for the fetus. The mother's liver is necessary for this, since the fetal liver is just developing and is not yet capable of many functions including removing metabolic wastes from the fetal bloodstream, storing minerals, and enzyme production. Because the fetal liver is underdeveloped, the fetus possesses blood vessels which transport blood around the developing liver rather than to and through it. This is necessary, since the small developing fetal liver cannot filter or handle the full quantity of blood that needs to be filtered. When the fetus is born, the placenta, umbilical vein and artery (jointly referred to as the umbilical cord) are severed and are no longer functional. Once the umbilical cord is cut at birth, there is no longer this connection between the mother and the just-born puppy. At this point, the puppy must rely on his own liver functions and not that of his mother.

At or about the time of birthing (whelping), the blood vessels within the fetus, which allowed blood to bypass the developing fetal liver, must close. Once these vessels close, the puppy's blood is forced to pass through the puppy's now developed liver. If these fetal vessels fail to close, then blood is allowed to abnormally be shunted around the liver, hence the name liver shunt. When blood is shunted around the liver rather than to and through it, the liver is not able to filter all of the blood, and therefore, toxic metabolic wastes such as ammonia are not adequately removed from the bloodstream. The degree to which blood is shunted around the liver is dependent on the extent to which shunting vessels persist. Liver shunts may be large allowing much blood to bypass the liver, or they may be partially closed allowing only small amounts of blood to shunt around the liver. The extent of blood shunting varies with every dog.

SYMPTOMS

The symptoms of liver shunts vary and are directly related to the extent of blood shunting. If the liver is receiving and processing 95 percent of the puppy's blood, the symptoms may be few, if any. More severe shunts are life threatening with many symptoms. Symptoms may be evident in these puppies at only a few weeks of age and may include low growth rates, vomiting, diarrhea, constipation, salivation, increased urination, seizures, and death. Dogs with less severe liver shunts may not exhibit any clinical signs until the puppy is much older, even up to a year.

RISKS

All liver shunts, whether mild or severe, are considered serious and life threatening. Even mild liver shunts generally exhibit greater symptoms as the puppy increases in body size. The larger the puppy the more metabolic wastes produced, and therefore, the more the liver is needed. Most affected dogs will not live a normal life expectancy unless the abnormality is correct.

MANAGEMENT
Management techniques for liver shunts have improved. The best and preferred treatment is to identify the abnormal blood vessels and surgically close them, eliminating the shunt. This will require sophisticated testing and may include radiographs (x-rays), laboratory blood analysis, ultrasound, and intravenous dye studies. The expense and results are variable depending on the degree of shunting, age, and symptoms. In addition to surgery, alterations in diet, and administration of medications are often beneficial. Restricted protein diets help reduce the production of the toxic waste, ammonia, and will therefore help lessen the need for liver detoxification. Owners and veterinarians should thoroughly discuss the seriousness, expense, and expected outcome associated with the management of all individuals suspected of having a liver shunt.

Hypoglycemia

Hypoglycemia simply means a low blood sugar. Glucose is the form of sugar found within the bloodstream. Glucose is formed during the digestion of foods and it can be stored within the liver in a storage form called glycogen. Most instances of low blood sugar (hypoglycemia) in the puppy are the result of inadequate nutrition; either not enough or poor quality (undigestible) food. Excessive exercise may also cause the body to use up more sugar than is available.

Symptoms

A puppy with hypoglycemia will lack energy. Glucose (sugar) is the fuel the body burns for energy; without it the puppy is listless. In severe instances, the puppy may even seizure, since glucose is necessary for the brain tissue and muscles to function. These hypoglycemic episodes will cause the puppy to fall over and appear weak or comatose.

Risks

The risks depend on the severity or extent of the lack of blood sugar. If it is due to lack of food or excessive exercise it can be easily corrected. If however, the underlying cause is more serious, such as liver disease preventing the storage of glucose as glycogen, or intestinal disease preventing the proper digestion and/or absorption of food, then hypoglycemia may be chronic and life threatening.

Management

If a puppy is listless due to low blood sugar, it is imperative to immediately provide sugar. Karo syrup and honey are excellent sugar sources and should be fed to the puppy. If the puppy fails to respond to sugar, or the hypoglycemic episodes are frequent, then a thorough exam by a veterinarian is in order. It must be determined if the low blood sugar is simply the result of inadequate nutrition or a more severe underlying disease.

LUXATING PATELLAS

A dog from one of the smaller breeds runs across the yard chasing a tossed ball. In mid-stride, he yelps in pain and pulls his left hind leg off of the ground. After a second, he continues limping on in a three-legged fashion. After ten minutes, the rear leg drops back down to the ground and he uses it normally. This episode occurs maybe once a week. It never really seems to bother him that much – a yelp of pain, a short period of lameness, and in a few minutes he is back to his old self. Typically, he is a small or toy breed such as a Chihuahua, Lhasa Apso, Pekingese, Pomeranian, Poodle.

A luxating patella may affect some animals much more severely. They may hold the leg up for several days and show considerable discomfort. Dogs who have a luxating patella on both hind legs may change their entire posture, by dropping their hindquarters and holding the rear legs farther out from the body as they walk. Those most severely affected may not even use their rear legs, walking by balancing themselves on their front legs like a circus act, or holding their hindquarters completely off the ground.

Normal knee anatomy

The patella is the bone we know as the knee cap. A groove in the end of the femur allows the patella to glide up and down when the knee joint is bent back and forth. In doing so, the patella guides the action of the quadriceps muscle in the lower leg. The patella also protects the knee joint.

Looking at the lower front portion of the femur (the thigh bone) in a normal dog, you will notice two bony ridges that form a fairly deep groove in which the patella is supposed to slide up and down. These structures limit the patella’s movement to one restricted place, and in doing so, control the activity of the quadriceps muscle.

The entire system is constantly lubricated by joint fluid. It works so that there is total freedom of motion between the structures.

What occurs when the patella is luxating

some dogs, because of malformation or trauma, the ridges forming the patellar groove are not prominent, and a too-shallow groove is created. In a dog with shallow grooves, the patella will luxate (jump out of the groove) sideways, especially toward the inside. This causes the leg to 'lock up' with the foot held off the ground.

When the patella luxates from the groove of the femur, it usually cannot return to its normal position until the quadriceps muscle relaxes and increases in length. This explains why the affected dog may be forced to hold his leg up for a few minutes or so after the initial incident. While the muscles are contracted and the patella is luxated from its correct position, the joint is held in the flexed or bent position. The yelp is from the pain caused by the knee cap sliding across the bony ridges of the femur. Once out of position, the animal feels no discomfort and continues his activity.

Symptoms

Most dogs are middle-aged, with a history of intermittent (on-again-off-again) lameness in the affected rear leg(s). An affected dog commonly stops and cries out in pain as he is running. The affected leg will be extended rearward, and for a while, the dog is unable to flex it back into the normal position.

Risks

Uncorrected, the patellar ridges will wear, the groove will become even shallower and the dog will become progressively more lame. Arthritis will prematurely affect the joint, causing a permanently swollen knee with poor mobility. Therefore, a good evaluation needs to be done by your veterinarian early in the condition to prevent long-term arthritic crippling.

Treatment

As would be expected, medical therapy has little corrective ability in this disorder and surgery is therefore required and is the treatment of choice. A surgical treatment is not necessary in every individual with this condition.

Surgery can alter both the affected structures and the movement of the patella. The groove at the base of the femur may be surgically deepened to better contain the knee cap. The knee cap itself may be 'tied down' laterally (on the outside) to prevent it from deviating medially (toward the inside). The bony protuberance at the site of the attachment of the quadriceps tendon on the tibia, may be cut off and then re-attached in a more lateral position. All of these procedures work well and the type performed depends on the individual case and the clinician. The animal should respond quickly after surgery and is usually completely recovered within thirty days, using his legs in normal fashion.

LEGG-PERTHES

Legg-Perthes disease is a disorder of small breeds of dogs, especially Yorkshire Terriers and West Highland White Terriers. With this condition, the puppy will grow normally until about three months of age. At this time, the ball (femoral head) of the hip joint begins to degenerate. It is believed that the blood supply to the femoral head decreases causing the bone to deteriorate and actually die. Similar conditions occur in humans. The end result is a malformed hip joint and secondary arthritis.

Symptoms

Even though the hip joint deterioration begins around three months of age, it is not until the puppy is six to ten months of age that it becomes lame. One or both hip joints may be involved. The dog will limp on the affected side(s).

Risks

The hip joint will never be normal and some lameness will always be present. Arthritis will be the result in the affected joint.

Management

Surgery to remove the diseased bone, i.e., the femoral head, is successful. The hip joint will not return to normal function, however, the destructive arthritic process will be greatly slowed. The secondary arthritis should be managed similarly to other forms of arthritis.

Collapsed trachea

The trachea is supported by tough rings made of cartilage. Occasionally, the trachea will lose its rigidity and collapse while the dog is breathing. For unknown reasons, the cartilage rings weaken and the trachea no longer has proper support. The collapsing trachea syndrome is most often seen in toy breeds, especially Toy Poodles over the age of five.

Symptoms

The symptoms of this syndrome depend on the severity of the deterioration. Usually, the dog will have difficulty breathing, especially during exercise. The deeper the pet tries to inhale, the more the trachea collapses, further restricting air flow (similar to sucking on a straw too hard). The pet appears to tire easily as it becomes short of breath. Dogs with a collapsing trachea will generally cough as if trying to clear the airways, and occasionally this cough will sound like a goose honk. In very severe cases, the tongue and gums will appear blue as breathing becomes restricted.

Risks

Most dogs suffering with the collapsed trachea syndrome live normal - but restricted - lives. Activity is generally limited because the ability to breathe deeply when exercising is hindered. Left untreated, the restricted air flow can put undue stress on the heart and lungs as they try to compensate for the inability to breathe properly. Obese dogs are at greater risk than others.

Management

Examination with the fingers and radiographs (x-rays) will generally confirm the diagnosis. Depending upon the severity of the condition, medications will help. Veterinarians usually prescribe drugs to help dilate the airways. The coughing is controlled by cough suppressants such as Torbutrol. If the pet is obese, we suggest a stricter diet. Finally, activity should be restricted and not encouraged. Dogs with collapsing tracheas should wear harnesses instead of collars in order to take any pressure off of the trachea. With the help of medication and modification of lifestyle, the collapsing trachea can be controlled but seldom cured. In severe cases, surgery to help open the airways may be beneficial, but most cases are managed medically not surgically.

Del-Rae Chihuahuas

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