Feeds:
Posts
Comments

Posts Tagged ‘veterinary’

First let’s talk about the thyroid gland. Dogs and cats have a divided thyroid gland located on either side of the trachea just below the larynx. Humans usually have just one gland more or less the shape of a butterfly. Some individual humans, dogs and cats can have ancillary thyroid tissue, usually small amounts, located along the trachea and airways. These are termed ectopic thyroid tissue and in some cases can maintain thyroid function if it is necessary to remove the thyroid gland surgically.

 

The thyroid gland is responsible for, or plays an important role in, many normal body functions. These include the regulation of body temperature, metabolism of fats and carbohydrates, weight control (both loss and gain), heart rate and cardiac output, normal function of the nervous system, growth and brain development in young animals, reproduction, muscle tone, and the condition of the skin and hair. So if the thyroid gland is not functioning normally we can expect changes in these functions and those changes result in symptoms or signs of the disease.

 

Thyroid disease is manifest as either low or absent thyroid activity (hypothyroidism) or excess thyroid activity (hyperthyroidism).

 

Signs of hypothyroidism include; weight gain, lethargy, generalized weakness, mental dullness, alopecia (loss of hair that can be generalized or in spots), excessive shedding, poor new hair growth, dry and/or dull hair coat, excessive scaling of the skin, recurring skin infections, and the inability to tolerate cold. In rare cases the animal may have seizures, a head tilt and infertility.

 

Signs of hyperthyroidism are, as one might expect, the opposite. There is a generalized increase in metabolism resulting in loss of weight despite an increased appetite. There is a general unkempt appearance and poor body condition. The animal may vomit and have diarrhea and frequently will be seen drinking water. This results in increased urine production. Some animals will have difficulty breathing and compensate with rapid shallow breathing. There is usually a rapid heart rate sometimes accompanied by so-called “gallop rhythm” a type of abnormal beat. The animals are usually hyperactive, and often the thyroid gland is enlarged.

 

Hypothyroidism is most common in middle-aged medium to large breeds of dogs. The condition is rare in cats. It is more commonly found in middle-aged dogs four to ten years of age. Anecdotal evidence seems to indicate that neutered males and females are at higher risk than intact animals. This condition is most commonly the result of inflammation of the thyroid gland or a decrease in active thyroid tissue from unknown cause(s). The condition can also occur as a result of treatment with the sulfa drug trimethoprim-sulfamethoxazole. In very rare cases iodine deficiency in dogs can result in hypothyroidism but commercially prepared dog and cat foods all contain adequate levels of iodine. The treatment for this condition is replacement therapy with levothyroxine or another type of thyroid replacement.

 

The diagnosis of hypothyroidism usually requires laboratory testing that includes a complete blood count, biochemistry profile, and urinalysis. Your veterinarian may be able to make an initial diagnosis based on the results of these tests, but it might be necessary to measure the levels of T3 and T4 and other endocrine lab tests. Your veterinarian may also recommend X-ray studies to check for other associated abnormalities.

 

Hyperthyroidism is the result of overproduction of thyroxin by the thyroid gland usually the result of a thyroid gland tumor. It can also be an aftermath of inappropriate overmedication for hypothyroidism. It is rare in dogs but can occur. It is most commonly diagnosed in older cats usually about thirteen years old or older. Less than five percent of cats with hyperthyroidism are under ten years of age. In addition to a thyroid tumor hyperthyroidism can also be the result of congenital disease, iodine deficiency or the result of inappropriate therapy. Sometimes it is impossible to identify the cause.

 

The diagnosis of hyperthyroidism is often initiated by palpation of an enlarge thyroid gland during a physical exam and documentation of clinical signs suggesting this disease. This will usually lead your veterinarian to measure a thyroid profile that includes T3, T4, Free T4 and TSH in the blood. If the T4 is higher than normal the diagnosis is confirmed however some early cases demonstrate T4 and the other hormone levels in the normal range. The performance of a T3 suppression test might be indicated and can produce a diagnosis. If the T3 suppression test results are still equivocal and if hyperthyroidism is still suspected further tests including nuclear isotope imaging may be necessary to arrive at a diagnosis.

 

There are three types of treatment for hyperthyroidism; life long oral anti-thyroid medications, surgical removal of affected thyroid glands and treatment with radioactive iodine. Tapazole (methimazole) is a specific anti-thyroid medication. This is a treatment that must be continued for the rest of the life of the animal unless surgical removal or radioactive iodine removal are indicated. Sometimes Tapazole treatment is used prior to surgery or radioactive iodine therapy to reduce thyroid hormone levels into the normal range to reduce the risk of surgery or radioactive isotope therapy. It is also indicated when the animal has congestive heart failure resulting from the hyperactive thyroid. Side effects from Tapazole include depression, vomiting, appetite loss and more seriously blood abnormalities. If surgical removal is the choice of therapy the surgeon must be very careful to avoid damage to the parathyroid glands. Removal or injury to these glands will result in significant problems.

 

As always if you suspect your animal has thyroid disease consult your veterinarian.

Read Full Post »

Dogs have been in close contact with humans for thousands of years. Estimates range from 9,000 to 30,000. Due to this long association dogs are thought to have the ability to not only understand but to communicate with humans. Many researchers in this field attribute these communication skills to the manifestation of unique traits that enables dogs to be acutely sensitive to cues supplied by their humans.

 

Recent research in canine cognition has shown considerable variability, depending upon the design of the experiment(s) and probably the agenda of the person(s) doing the research but it seems clear that at least some dogs can and do follow pointing and gaze cues, can fast map novel words and according to some studies have emotions. Since they cannot communicate with us with spoken language researchers have mostly had to closely observe behavior in a wide variety of experimental designs and infer how the canine brain functions by speculation.

 

Now we can use functional magnetic resonance imaging (fMRI) to study brain function. Gregory S. Berns, MD, PhD is a neuroscientist and director of the Center for Neuropolicy at Emory University. He recently published a book entitled: HOW DOGS LOVE US: A neuroscientist and his adopted dog decode the canine brain. He describes in this book and in articles published in scientific journals how his group trained dogs to lie still in the MRI machine while fully awake and found that the reward-prediction error hypothesis of the dopamine system provided a concrete prediction of activity in the ventral caudate of the dogs studied, i.e. the dogs were able to respond to specific hand signals associated with either giving a food reward or withholding it. During the experiment the dogs were not given the reward, just the hand signals they had been conditioned to. The results demonstrated the specific areas of the brain that anticipated the pleasurable reward. These same brain locations have been associated with dopamine release in many studies conducted in awake humans and primates. There was significantly less dopamine sensitive response when the withholding reward signal was given. The interpretation of these results indicates the dogs brains responded THINKING they were going to receive the treat.

 

Dr. Berns and his research group believe they can extend these studies to characterizing many questions about our ability to communicate with dogs including their ability to respond to human facial expressions and how dogs process our spoken words. Perhaps we are on the verge of understanding how dogs respond to our emotional state and perhaps if and how they grieve for a lost loved one. Maybe we can even find out if they really do love us or just manipulate us so we will feed them.

Read Full Post »

Sidney, Montana, the summer of 1960. Ike Williams and Jon Wilkins were partners, the owners of Williams & Wilkins Blacksmiths and Mechanics. Their shop was large, chaotic and dirty. It occupied the entire frontage of their property hiding their small, immaculate, frame house. The shop and their considerable skills shielded them from the necessity of acknowledging their relationship, something the community had no real need or desire to hear or talk about. The partners were able to repair and, if necessary, fabricate parts for any type of motorized or pulled agricultural implement. That was what the community considered important. They had lived and worked together in Sidney for twenty-five years before my new bride and I arrived. I was a recent graduate and new associate veterinarian in the only veterinary practice within a fifty-mile radius.

Like an old married couple Ike and Jon finished each other’s thoughts, knew how to avoid conflict, were comfortable in their own skins, and with each other. All necessary accommodations had been made.

They both loved cats. I was never able to determine exactly, or even approximately, how many cats they had. There were shop cats, outside cats and house cats, all well cared for.

From time to time one or both of them would bring in a house or shop male for castration or a female to be spayed. All received annual vaccinations. I guess they had a method for deciding which cats would occupy which spaces. The outside cats were free to reproduce but each new litter of kittens was brought in for vaccinations and caring homes were found for them.

They were both sitting in the waiting room when I returned from doing rectal exams on twenty-five head of half-wild range cattle to check for pregnancy. I rubbed my sore left arm as I greeted them.

“Mr. Williams, Mr. Wilkins, what have you got for me today?”

They stood up as if joined at the hip. Wilkins held a huge tabby in his arms. The cat was whimpering obviously hurting.

“This is Wilma, she’s a house cat. Old Doc spayed her for us several years ago and she’s had all her shots every year. Today when we came in for lunch we found her, crying in pain. She’s paralyzed.”

As he talked tears welled up in Wilkins’ eyes. Ike put his arm over his partner’s shoulders.

“It will be OK Jon. Young Doc is good everyone says so. He’ll take care of Wilma for us, won’t you Doc?”

I held out my hands.

“Here, let me take her. Let’s go into the exam room and see what we can figure out.”

Wilma was too soft, too fat, and too lazy. Both hind limbs were flaccid. She meowed louder with Jon no longer holding her. She was also hyperventilating. I examined her carefully, noting that the white nails on her hind paws were tinged blue and the paws were cold to the touch. I was unable to palpate a pulse in either femoral artery.

“This is not good,” I told them. “I’m pretty certain she has what we call a saddle thrombus. It’s a blood clot blocking the two main arteries to her legs. I’ve never seen a case but I remember the description from vet school. All the signs are there. She is paralyzed in the hind legs, in obvious pain and there is no blood circulating to her hind legs.”

“Is there something you can do to fix her?” asked Ike.

“Well, theoretically I could operate and remove the clot. However, I’ve never done anything even remotely like that before, never actually opened an artery on purpose then tried to suture it closed afterwards. I don’t think we even have any suture material small enough to do that kind of thing. Also we have no idea what causes this and it could come right back. I’m sorry. I hate to say this. My job is to help animals not kill them. In this case I think the best thing I can do to help Wilma is to put her out of her misery.”

They were devastated.

“Are you sure you don’t want to even try?” pleaded Jon. “Cost is not a problem you know. We’ll pay whatever it costs,” he looked to his partner for confirmation. Ike nodded his agreement.

“OK, I’m willing to try anything, but I have to make certain you know this could be a disaster. I’ve never even seen anything like this done. First let me look to see if we have any suture material small enough to close an artery.”

I was apprehensive as I searched through the cabinet of surgical supplies. I found one packet of 4-0 silk, with needle attached. It looked to be several years old. I had no idea where it came from or for what my boss intended for it when he bought it. I came back into the exam room and held up the packet.

“This might work, but it’s old and I’ll need to sterilize it again, I have no idea how long it’s been around, the package says it expired two years ago. You guys are certain you want me to try this? I don’t really know what I’m doing. I’ll have to dissect down to the end of the aorta, that’s the main artery coming from the heart, where it branches to supply blood to both hind legs and the tail. Then I have to find the blockage, try to put a tourniquet around the artery above the obstruction, open the artery, remove the clot and suture the artery closed. Chances are very good Wilma will bleed to death while I’m fumbling around.”

“But she’ll be anesthetized, right Doc? She won’t feel anything? Ike asked.

“That’s correct,” I said. “As soon as I anesthetize her she’ll feel no more pain, until and unless we remove the clot and get everything repaired and let her wake up again. She could still be in a lot of pain after I’m done with the surgery, I don’t know.”

“But you can give her something for post-operative pain, right?” Jon pleaded.

“Sure, sure, we can treat post-op pain.”

“OK Doc. Go for it. Is it OK if we wait here? We already put a sign on the shop door saying we wouldn’t be back until tomorrow.”

“Sure, you’re welcome to wait here. It will take me some time to put a surgical pack together to sterilize with the suture material. I have to think about what I might need by way of instruments. I know we don’t have any specialized vascular surgical instruments or suction so I’ll have to improvise. I’ll let you know before I get started. Let me give her just a touch of tranquilizer to see if we can make her more comfortable. I’m afraid to give her anything like a full dose because her heart rate is so fast. The tranquilizer will slow her heart rate and the high heart rate may be the only thing keeping her alive.”

I got Wilma anesthetized, hooked up an intravenous drip, opened up her abdomen, packed off her abdominal organs and found the distal aorta. When I tried to dissect around the aorta I managed to break off some small branches and the abdomen quickly filled with arterial blood. The turkey baster I added to the pack was not an adequate suction device and Wilma bled out in short order. It was the unmitigated disaster I had feared.

Today we know that saddle thrombus is almost always associated with a disease called dilated cardiomyopathy. This is a condition, probably with genetic predisposition, that is uncommon but not rare in cats. The heart is enlarged and dilated and it doesn’t function properly. Normally blood is always moving inside the heart. This constant motion of the blood, even when the heart is resting between beats, helps prevent clots from forming. Because the heart is dilated and unable to beat strong enough areas of flow stasis develop within the heart chambers. Areas of flow stasis allow clots to develop. When the clot becomes large enough it is eventually washed out of the heart. It flows downstream until it lodges at a location too small for the size of the clot, usually at the terminal trifurcation of the aorta. Modern veterinary surgeons can deal with this, providing the underlying heart disease is treatable. Today, if diagnosed early enough and if the underlying heart disease is controlled, many of these animals can be saved and will go on to live a reasonably normal life. In 1960 my saving Wilma would have been a miracle.

Ike and Jon understood and were even appreciative that I tried.

I felt guilty and depressed, never acclimated to losing an animal, especially through my own clumsiness.

Excerpt from “Animals Don’t Blush”

Read Full Post »