Friday, January 13, 2017

Body Parts - the Feline Heart

Body Parts – the Feline Heart

            The heart is the main organ in the circulatory system.  Its job is to pump blood throughout the body, supplying oxygen and nutrients to the tissues.  Similar to the human heart, the feline heart has four chambers.  The two chambers on the top of the heart are the atria (plural for atrium).  The two chambers at the bottom of the heart are the ventricles.  The left atrium and left ventricle are separated from the right atrium and right ventricle by a dividing wall called the septum.

            Listening to your cat’s heart with the stethoscope is one of the most important parts of the veterinary exam.  The normal heart rate in a cat is 160 to 240, which is much faster than a human’s.  Cats are often nervous during the veterinary visit, so it’s not unusual to find heart rates in the 200’s.  The rhythm should be regular and the heartbeat should be easily heard.  Abnormalities in the heart rate and rhythm are fairly uncommon.  The most common abnormality heard with the stethoscope is a heart murmur.  A murmur is the sound of turbulent blood flow and may be an indicator that something is amiss.

            Coronary artery disease is the most common cause of death in humans in the U.S.  Fortunately, cats don’t get coronary artery disease. Nature, however, doesn’t play favorites when it comes to other heart diseases, and cats are indeed susceptible to disorders of this vital organ.  Therefore, the discovery of a heart murmur during your cat’s physical examination warrants further investigation.  It can be difficult for a veterinarian to know just by listening whether a feline heart murmur is merely a physiologic finding (i.e. there’s actually nothing wrong with the heart), or a pathologic finding (i.e. there is indeed something wrong with the heart). Physiologic murmurs are benign and can be caused by things such as stress, excitement, pain, or fever.  The only way to tell if a murmur is benign vs. pathologic is to perform echocardiography (sometimes also called a sonogram, or cardiac ultrasound).

            Echocardiography is best performed by a veterinary cardiologist. (Yes, there are veterinarians that specialize in cat and dog tickers only.) These cardiologists know exactly how thick or how thin the walls of each heart chamber is supposed to be, how fast the blood should be flowing as it travels out of the aorta and pulmonary artery, and how strongly the heart is supposed to be contracting.  By viewing the heart using ultrasound and taking a variety of measurements, the cardiologist can determine if heart disease is present.

            The most commonly diagnosed heart disease in cats is a condition called hypertrophic cardiomyopathy (HCM).  In cats suffering from HCM, the walls of the heart become progressively thicker, with one particular chamber, the left ventricle, usually becoming the most affected.  Think of the left ventricle as a coffee mug.  Now imagine the walls of the mug becoming thicker and thicker, growing inwardly.  The mug would hold less and less coffee.  In HCM, the ventricle holds less and less blood.  If the ventricle can now hold only half as much blood, the heart will try to compensate by pumping twice as hard to achieve the same effect.  Eventually, the muscle starts to give out, and congestive heart failure may develop.  Other complications, however, may arise before heart failure ever develops.  The most serious complication of HCM is a condition called aortic thromboembolism, abbreviated ATE.  In ATE, a blood clot develops in the left atrium.  A piece of the blood clot breaks free, travels down the aorta, and gets lodged at the very end, where the aorta branches to supply the legs with blood.  Cats become acutely paralyzed in the rear legs as a result.  This is a truly devastating complication that carries a very grave prognosis.  Sadly, as a feline practitioner, I have the terrible misfortune of seeing two or three cases of ATE a year, and every case ends disastrously. Sigh.  Cats diagnosed with HCM are usually prescribed a variety of medications aimed at slowing the progression of the disorder and reducing the risk of ATE, and many cats do well for many years after the diagnosis with no symptoms at all.

            HCM can strike any breed of cat, however, Maine Coons and Ragdolls are predisposed to the disorder.  Fortunately, the reason for their susceptibility was discovered several years ago: a mutation in the gene that codes for a specific protein in the heart.  A genetic test has been developed to screen cats for the disorder.  The test requires either a cheek swab or a blood sample. Responsible breeders can now test their cats for this mutation, and use selective breeding techniques to hopefully eliminate the gene from the population.

            Kittens will sometimes have a heart murmur that disappears as they mature.  A persistent murmur in a kitten, however, should be investigated, as congenital heart diseases occasionally do occur, and the sooner they are diagnosed and treated, the better the prognosis. 



Monday, January 2, 2017

Disorders of the Feline Esophagus

Disorders of the Feline Esophagus

            Last week I examined a cat that was brought to my feline-only veterinary practice for a gastrointestinal problem.  I asked the client what her main concern was, and she said that the cat was regurgitating frequently.  I asked if the cat was truly regurgitating, or if he was vomiting.  She said, “I didn’t realize there was a difference”. 

            I would venture that most people incorrectly believe that vomiting and regurgitating are synonymous.  Vomiting is the forceful expulsion of stomach contents through the mouth.  When animals vomit, the forceful contractions of the stomach are clearly visible.  Regurgitation, on the other hand, is the ejection of undigested food from the esophagus, the tube that connects the mouth and the stomach.  (In lay terms, we often call the esophagus the “food pipe”, similar to the way we call the trachea the “windpipe”.) Regurgitation is a passive process; the animal leans forward, puts its head down, and the esophageal contents are expelled.  Unlike vomiting, there is no salivation, retching, or violent abdominal contractions.  The two processes are completely different, and so are the disorders that cause them. 

            Upon further questioning of my client, it was apparent that the cat was actually vomiting, and this was no surprise.  Esophageal disorders are much less common than disorders of the stomach and intestines in cats.  Table 1 is a list of the most common esophageal disorders in cats.

            Megaesophagus is a condition in which the esophagus is weak and unable to propel food from the mouth to the stomach.  The esophagus becomes flaccid and large (hence the “mega”, derived from Greek, meaning “large”).  There are several causes of megaesophagus in the cat, such as congenital and hereditary disorders (Siamese cats are predisposed) and neuromuscular disorders (such as dysautonomia and myasthenia gravis).  In most cases, the underlying cause is never identified.  Regurgitation is the most prominent sign in cats with megaesophagus.  If megaesophagus is secondary to a neuromuscular disorder, other signs, such as weakness, muscle pain, and muscle atrophy may be present.  Some cats with megaesophagus will regurgitate food into their mouths and then accidentally inhale some food into their lungs, leading to aspiration pneumonia.  Additional clinical signs associated with aspiration pneumonia include fever, labored breathing, and coughing.   Diagnosis of megaeophagus can often be made via radiology (x-rays).  Administration of barium before the x-rays are taken greatly enhances the visualization of the esophagus, aiding in the diagnosis.  Treatment of megaesophagus consists mainly of supportive care, except in those rare cases where a treatable underlying cause has been identified.  Supportive care involves feeding frequent small meals with the cat in an upright position.  The cat is trained to eat from a bowl placed on an elevated platform.  Ideally, the cat is held upright for 10 minutes after eating so that gravity may assist the movement of food into the stomach.  Liquefied food works best. 

            Esophageal foreign bodies are occasionally seen in cats.  The most commonly swallowed objects are fishhooks, sewing needles, and bones.  Depending on the type of the object, the size and shape, and how long the object has been there, foreign objects can cause significant damage to the esophagus.  Clinical signs are an acute onset of gagging, retching, salivation, repeated swallowing, and regurgitation. (Table 2) Perforation of the esophagus by the foreign body is a serious complication and can cause fever, pain, coughing, labored breathing, and abscess formation. Because the likelihood of complications increases with time, identification of a foreign body should be treated as an emergency.  Most esophageal foreign bodies are visible on x-rays.  Once identified, the foreign body should be retrieved using an endoscope.  As the endoscope is passed into the esophagus and the object is seen, grasping forceps can be employed to snare it. Care must be taken to avoid creating further damage when sharp objects are removed.  If the object cannot be extracted orally, an attempt should be made to push it into the stomach, where it can be removed via abdominal surgery.   If the object cannot be removed orally or advanced into the stomach, then esophageal surgery is required.  Esophageal surgery is much more complex and expensive and has a markedly worse prognosis. 

            Gastroesophageal reflux disease (GERD) is common in people, but uncommon in cats.   It occurs when acid from the stomach refluxes, i.e. leaks backward, into the esophagus.  It is sometimes seen as a complication after anesthesia; when cats are anesthetized, the sphincter muscle between the stomach and esophagus may relax, allowing caustic gastric juice to enter the esophagus.  Conditions that cause chronic persistent vomiting, as well as anatomical conditions, such as a hiatal hernia (see next section), can also lead to acid reflux and esophageal damage. The clinical signs of GERD are similar to those of megaesophagus (Table 2).  Radiographs aren’t very helpful in the diagnosis.  The best diagnostic test is endoscopy.  The endoscope allows you to visualize the lining of the esophagus.  Affected cats will often show severe redness and inflammation, erosions, ulcers and possibly hemorrhage.  In some cases, the junction between the esophagus and stomach is seen to be wide open (in normal cats, it is closed) and reflux of gastric contents may actually be observed during endoscopy.  The goals of treatment are to prevent reflux, decrease the acidity of the stomach contents, promote healing of the damaged esophagus, and control infection.   To prevent reflux, drugs that tighten the sphincter between the esophagus and stomach and promote gastric emptying are given.  The most common are metoclopramide (Reglan) and cisapride.  To reduce gastric acid, drugs called H2-receptor blockers may be given.  Familiar ones are cimetidine (Tagamet), ranitidine (Zantac) and famotidine (Pepcid).  Famotidine is ideal for cats in that it can be given once daily.   More potent acid inhibitors, such as omeprazole (Prilosec) or pantoprazole (Protonix) may be indicated in severe cases.  Sucralfate (Carafate) is an oral drug that, if compounded as a liquid, binds selectively to erosions in the esophagus, acting as a barrier or “Band-Aid” against damage from stomach acid.  Antibiotics are usually administered to prevent or control infection by oral bacteria that may colonize the eroded areas in the esophagus.  A potential complication of foreign bodies and reflux disease is the development of a stricture (discussed below).

            The diaphragm is a muscle that separates the chest cavity from the abdomen.  There is an opening in the diaphragm, called the esophageal hiatus.  The very end of the esophagus passes through the hiatus and gives rise to the stomach, which is on the abdominal side of the diaphragm.  A hiatal hernia occurs when part of the stomach pushes through the hiatus and goes into the chest.  Sometimes the herniated piece of stomach moves back and forth through the hiatus (a “sliding” hiatal hernia); in other cases, the stomach goes through the hiatus and gets stuck there.  In most cases, it is a congenital condition, i.e. cats are born with it.  Some cats acquire the condition later in life, sometimes secondary to trauma.  Hiatal hernias cause acid reflux and many or all of the clinical signs described in the previous paragraph.  Diagnosis is usually made via radiographs, especially if the hernia is persistent (i.e. not sliding).  On the radiograph, a small portion of the stomach will be visible on the chest-side of the diaphragm.  Treatment requires surgical correction of the hernia, as well as administration of antacids and protectants.

            Esophageal stricture is an abnormal narrowing of a portion of the esophagus.  Strictures can develop after any severe injury to the esophagus, but they most commonly occur as a complication of reflux esophagitis and foreign bodies.  Certain drugs given by mouth in tablet or capsule form can result in esophageal damage and stricture if administration is not followed by a small amount of water or food, most notably the antibiotics clindamycin and doxycycline hydrocholoride.  Strictures develop slowly, so the clinical signs usually include progressively worsening inability to eat solid food, regurgitation immediately after eating, and weight loss despite an excellent appetite.  Diagnosis can usually be made via radiography after administering barium.  Barium outlines the internal portion of the esophagus and allows visualization of the stricture and assessment of the length and number of strictures present.  Endoscopy is useful for identifying strictures as well as for treatment.   Balloon dilation is a procedure in which a catheter with a deflated balloon at the tip is advanced into the stricture with the cat under anesthesia.  The balloon is then inflated, opening up the stricture.  The procedure is repeated at 5-7 day intervals.  Hemorrhage or perforation is an occasional complication.  Some cats do well, but in many cats, the stricture reforms.  In these cases, surgery may be attempted, but a guarded prognosis must be given.

            Cancer of the esophagus is rare in the cat.  The most common cancer seen is squamous cell carcinoma, usually in elderly cats.  Other tumors, such as sarcomas and plasmacytomas are seldom seen.  Because these tumors grow slowly, the clinical signs are similar to those seen in cats with esophageal strictures, i.e. slowly progressive onset of regurgitation, salivation, retching and difficulty swallowing.  Radiographs may reveal a soft tissue mass in the region of the esophagus, which is often made more visible if barium is administered before the radiograph is taken.  Endoscopy not only allows visualization of the tumor, but also allows biopsy specimens to be obtained for definitive diagnosis.  Surgical removal is the only treatment option, although the prognosis is poor, as the tumor may be too extensive to be removed. In many instances, the tumor has metastasized to other parts of the body.

            Disorders of the esophagus are uncommon in cats.  It is important that veterinarians distinguish vomiting from regurgitation in their patients. It should be re-emphasized that administration of any dry tablet or capsule to a cat should be followed by a small amount of water or food, to prevent esophageal irritation and possible stricture formation.

Table 1 – Common disorders of the esophagus in cats

Esophageal foreign bodies
Reflux esophagitis
Hiatal hernia
Esophageal stricture
Cancer of the esophagus

Table 2 – Common clinical signs of esophageal disease

Excessive salivation
Painful swallowing

Exaggerated or repeated swallowing motions

Tuesday, December 20, 2016

Body Parts - The Claws

Body Parts – The Claws

            Cat feet are fascinating.  They function as shock absorbers when landing after aerial acrobatics.  The pads on the paws are thick, with a substantial amount of adipose (fat) tissue just below the pad surfaces.  This acts as a cushion, allowing for cats to walk quietly.  To me, however, the most impressive parts of the feet are the claws. 

            All members of the family Felidae have claws.  The claws are retractable.  When the foot is relaxed, the claws remain sheathed by a layer of modified skin, which is surrounded by the fur on the toes.  Keeping the claws sheathed helps prevent wear and tear by minimizing contact with the ground.  When necessary, cats can voluntarily extend the claws on one or more paws.  The most common reasons for exposing their claws are hunting, self-defense (often against veterinarians, unfortunately), climbing, “kneading”, and for extra traction, like when my new kitten dashes across our expensive Persian rug.

            Cats typically have five toes on their front paws and four toes on their back paws, and each of these toes has a claw associated with it.   Not all cats conform to the formula of five toes in the front and four in the back, however.  A naturally occurring genetic mutation occasionally occurs, causing cats to have extra toes.  This is called polydactylism.  My adult cat, Mittens, is polydactyl, hence her corny name.  As you can see in the photo, it’s an appropriate moniker.  Her feet are huge! 

            I see a fair number of claw injuries in my feline-only veterinary practice.  The most common are broken nails and overgrown nails.  Broken nails often occur because the claw becomes entangled in a carpet or thick fabric.  When the cat pulls the foot loose, the nail can tear.  Sometimes, the nail gets completely torn off. In most cases, the nail is only partially torn off and is dangling, causing pain or discomfort every time the nail touches anything.  Torn nails are uncomfortable for the cat because after a tear, the underlying tissue, called the quick, becomes exposed.  The quick contains blood vessels and nerve endings and is sensitive.  A torn nail often causes the cat to limp on the affected foot.  In severe cases, the cat may refuse to bear any weight at all on the foot.  Treatment for a partially torn nail involves removal of the dangling piece of nail by your veterinarian.  Because cats scratch around in their dirty litter boxes with their feet, the exposed quick is at risk of becoming infected.  Your veterinarian may prescribe antibiotics and possibly pain medication.  A new nail often regrows from the exposed quick, however, that nail may end up looking malformed compared to the others.

            If a cat’s claws aren’t trimmed regularly, the claw can grow long enough that it actually curves all the way around and can pierce the pad of the affected toe.  The wound that occurs may get infected, causing pain and discomfort to the cat.  Treatment requires trimming the offending claw.  This should be performed by your veterinarian and should not be attempted at home.  If the pad is infected, your vet will prescribe antibiotics.  In some cases, soaking the foot in an antiseptic solution may be beneficial.  Overgrown nails seem to happen only in the front feet.  The rear nails are shaped differently.  Rear claws may grow very long if untrimmed, but they grow outwardly rather than curving down and around.  

Overgrown claws can be prevented by keeping your cat’s nails trimmed.  Arden Moore, in her book “Fit Cat”, gives a few quick and easy steps for giving your cat a “pet-icure”:

·      Get the equipment you need: nail clippers designed specifically for cats, a thick towel, and styptic powder (in case you trim a nail too short and it bleeds)

·      Wrap your cat in a large bath towel, exposing one foot at a time.

·      Position your thumb so that it rests on top of one paw, with your fingers of that hand underneath.  Gently press on the top of one of the toes to expose the nail.

·      Snip the clear, white tip of the nail.  Do not cut too close to the pink part (the quick), or you might nick the vein that runs through the nail, causing bleeding.

·      If you do nick the quick, apply a little styptic powder to stop the bleeding.  If you don’t have styptic powder, direct pressure on the nail with a tissue or paper towel will stop the bleeding quickly.

·      Give lots of praise to your cat during the nail trimming session, so that your cat might see it as a positive experience.

            To make nail trimming less stressful for your cat, start them young.  Play with your kitten’s feet regularly to get them used to being handled.  Gently squeeze the footpads to expose the nails, and then release.  Give a healthy treat after handling the feet.  Cats who have had their feet handled frequently as kittens are more amenable to nail trimming.  Some cats, however, simply will not allow their owner to trim the nails.  In these cases, taking the cat to your veterinarian or to a groomer should solve the problem.   Claws should be trimmed approximately every six to eight weeks.


Monday, December 19, 2016

The Feline Adrenal Glands

Body Parts – the Adrenal Glands

            I would venture that most people have heard of the adrenal glands.  I would also bet that if asked about what the adrenals do, most folks would correctly guess that they make adrenaline, the "fight or flight" hormone that makes your heart race before that first big plunge on the roller coaster.   But the adrenals do so much more than just make adrenaline.  These small glands are impressive little hormone factories, producing substances that control electrolytes, influence blood pressure, manage stress, and help regulate blood sugar.

            The adrenals, as their name implies (from the Greek: ad = on top of, renal = kidney) are located just above each kidney.  The gland is comprised of two parts, the outer portion, called the cortex, and the inner portion, the medulla. 

            The cortex can be subdivided even further, into three layers.  Each later produces different hormones.  The outermost layer produces aldosterone, a hormone that controls blood pressure by adjusting the level of sodium and potassium in the body.  The middle layer produces cortisol, a steroid hormone that regulates metabolism and helps the body manage physiologic stress.  The inner layer produces sex hormones such as estrogen and progesterone, (although the majority of the sex hormones come from the ovaries and testes.)
            The medulla is where adrenaline (also known as epinephrine) is manufactured by the body.   As mentioned above, this hormone helps the body spring into action in an emergency by increasing heart output and blood pressure, and raising the blood sugar.

            Fortunately, cats are much less susceptible to adrenal disorders compared to dogs.   Many veterinarians forget to even put adrenal disorders on their list of possibilities when dealing with cats, causing these ailments to be underdiagnosed in cats.  The three most common of these uncommon conditions are Cushing’s disease, Addison’s disease, and Conn’s disease.

            Cushing’s disease (the proper name is hyperadrenocorticism) is a condition in which the adrenal gland is producing too much cortisol.   There are two main reasons for this: either the pituitary gland is telling the adrenals to make more cortisol than it should, or there’s a tumor of the adrenal gland that is producing cortisol uncontrollably.  In cats, the pituitary is the culprit 80% of the time.  Cortisol-secreting adrenal tumors in cats are very rare.    The main signs of feline Cushing’s disease are excessive thirst and urination, weight loss despite a voracious appetite, a pot-bellied appearance, hair loss, and thin papery skin.  Diagnosis is made by special blood tests and imaging techniques like ultrasound or CT scanning.  There are medications that can be given to control cortisol secretion from the adrenals, however, if an adrenal tumor is the cause of the condition, surgical removal of the tumor might offer the best chance of treatment.

            Addison’s disease (hypoadrenocorticism) is basically the opposite of Cushing’s disease.  In this condition, the adrenal gland is making an inadequate amount of hormones.   In most cases, the adrenal produces insufficient aldosterone and insufficient cortisol.  In some cases, however, the adrenal produces inadequate cortisol only.  This is known as “atypical” Addison’s disease.   Clinical signs of the disorder are non-specific and include poor appetite, lethargy, weakness, vomiting, and diarrhea. Routine bloodwork may suggest the presence of Addison’s disease, however, a special blood test, called an ACTH stimulation test, is necessary for a definitive diagnosis.  Treatment requires administration of the deficient hormones.

            Conn’s disease (hyperaldosteronism) is an adrenal disorder in which the adrenal cortex produces excessive amounts of the hormone aldosterone. It is the most common adrenal disorder in cats.  [Note: the other two feline adrenal disorders are commonly referred to by their eponyms, Cushing’s and Addison’s.  For some reason though, hyperaldosteronism is rarely called Conn’s disease in veterinary medicine. Convention, I suspect.]   Excessive aldosterone will cause the blood sodium level to rise and the potassium level to drop.  This can lead to dangerously high blood pressure as well as severe muscle weakness.  The most common cause is a tumor of the adrenal gland.  In cats, about half of these tumors are benign, and half are malignant.  Routine blood tests may be suggestive of hyperaldosteronism, but a definitive diagnosis often requires measurement of aldosterone levels in the bloodstream as well as some form of diagnostic imaging, such as ultrasound or a CT scan, to better assess the adrenals.   Treatment can be either medical or surgical.  Surgical removal of the adrenal tumor can potentially cure the condition, however, surgery isn’t always an option either due to cost, anesthetic risk to the cat, or invasion of the tumor into the vena cava (a major blood vessel) making surgery too dangerous.  For cats that are poor candidates for surgery, medical management is recommended.  This involves controlling the blood pressure with a drug called amlodipine, administering another drug called spironolactone which counteracts the effects of the aldosterone, and supplementing the diet with extra potassium, so as to maintain a normal blood potassium level.  The dosages of these drugs may need to be increased as the disease progresses over time.  If the tumor has not spread and it can be completely removed, the prognosis is excellent.  Cats undergoing medical management may do well for many months or even years, as long as they receive their medication and are monitored closely.

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