Wednesday, March 22, 2017

Ascites (abdominal effusion) in Cats


Accumulation of fluid in the abdomen is an important sign of illness in cats

            Ascites (pronounced “a-site-eez”) is the accumulation of fluid in the abdominal cavity.  It is a sign of disease, rather than a diagnosis.  Unfortunately, there are very few benign causes of ascites. 

            Because there are so many possible causes of ascites, the historical findings vary in each individual case.  For example, a cat with ascites and a history of trauma (falling from a height, or hit by a car) could have internal bleeding, the fluid in the abdomen being blood, or a ruptured bladder, the fluid being urine.  Cats with labored breathing and exercise intolerance could be suffering from heart disease, another potential cause of abdominal fluid accumulation.  It is therefore important to get an accurate history from the cat owner as to the cat’s appetite, behavior, travel history, potential for trauma, etc.

            Cats with ascites are usually presented to the veterinarian with a complaint of abdominal distention.  However, there are other causes for a big belly in cats besides fluid accumulation, for example, abdominal tumors, enlarged organs such as a big liver or a big spleen, or an enlarged bladder due to a urinary obstruction.  The physical examination may yield other clues as to the cause of the ascites.  Cats with a heart murmur and weak pulses may have heart failure as the cause of their ascites.  Cats with peripheral edema (swelling of the limbs) may indicate that a low protein level in the bloodstream, another cause of fluid accumulation.   Some cats don’t seem to be bothered by ascites, while others are clearly uncomfortable.  Much depends on the volume of fluid that has accumulated.  Large amounts of fluid can put pressure on the diaphragm, limiting the expansion of the lungs and making it difficult to breathe.

            Determining the cause of the ascites requires various diagnostic tests.  X-rays of the abdomen are not very useful because the presence of fluid obscures the details of the other abdominal organs.  Abdominal ultrasound, however, allows for confirmation of the presence of fluid, and allows the veterinarian to evaluate the other abdominal organs, e.g. the liver, spleen and pancreas for potential causes of ascites.

            Analysis of the abdominal fluid can be very helpful in determining a cause for the ascites.  A fluid sample can be obtained by inserting a 20 or 22-gauge needle into the abdomen and withdrawing a sample with a syringe.  This technique is more successful when there’s a large volume of fluid present.  If there’s only a small volume of fluid present, ultrasound may help localize the fluid, allowing for successful sampling.  Most cats with ascites do not require complete removal of all fluid.  In some patients, the increase in pressure inside the abdomen from the fluid build-up actually prevents further accumulation, and if a lot of fluid is removed, it may re-form rapidly.  This can lead to a rapid decrease in the blood volume, leading to cardiovascular collapse and shock.  If the amount of fluid present is causing respiratory difficulty, enough fluid should be removed so that breathing is no longer compromised.  Fluid samples should be sent to a clinical pathologist for evaluation.

            If the underlying cause of the fluid can be identified and corrected, the fluid may be partially reabsorbed back into the bloodstream.  In cases of hemorrhage, as many as 50% the red blood cells can go back into the circulation. 

            Clinical pathologists often classify the fluid into one of three major categories: exudate, transudate, or modified transudate, based on the amount of protein and cells in the fluid.  Most samples end up being modified transudates, however, there is a lot of overlap between categories, and most practitioners don’t fine this classification very useful.  A more practical classification attributes the ascites to one of 7 disease categories:  cardiac, cancer, liver, kidney, urinary tract trauma, feline infectious peritonitis (FIP), and peritonitis (inflammation of the lining of the abdomen).

            Heart disease isn’t a major cause of ascites in cats, compared to dogs.  Prior to 1987, heart disease was a significant cause of ascites in cats, mainly due to the disease dilated cardiomyopathy (DCM), which was fairly prevalent.  Once it was discovered that a deficiency in the amino acid taurine was the primary cause of feline DCM, pet food manufacturers corrected the deficiency in the food and the incidence of DCM dropped dramatically. 

            Sadly, cancer is a common cause of abdominal effusion in cats, and is more common as cats get older.  In most cases, the initial tumor is a carcinoma, typically involving the gastrointestinal tract or pancreas.  The tumor metastasizes throughout the entire abdomen, a condition called carcinomatosis, and this often leads to ascites. 

            Feline infectious peritonitis (FIP) is a terrible viral disease that commonly causes abdominal fluid accumulation.  Any age cat is susceptible, although young cats are more commonly affected.  Unfortunately, FIP is not treatable and cats invariably succumb to the disorder. 

            Severe liver disease may cause ascites in cats.  The liver produces albumin, a protein that is important in helping maintain fluid within the circulation.  If the liver is very diseased, it may produce inadequate amounts of albumin, resulting in hypoproteinemia, a reduced level of protein in the blood.  This can lead to ascites.

            Pancreatitis is a common cause of ascites in cats.  In acute, severe cases of pancreatitis, fluid leaks through the vessels within the inflamed pancreas, into the abdominal cavity.  Pancreatitis used to be difficult to diagnose in cats, however, better ultrasound equipment and the development of a blood test called the fPLI test has made pancreatitis less difficult to diagnose. 

            Unfortunately, the disorders that cause ascites in cats tend to be bad, and the prognosis is usually guarded or poor.  Cat owners who think their cat might have a distended or enlarging abdomen should seek veterinary advice immediately, as early detection and prompt diagnosis may lead to a better outcome. 

Possible causes for ascites

Trauma and internal bleeding
Blood clotting disorder
Bleeding tumor
Urinary tract rupture
Feline infectious peritonitis
Heart disease
Liver failure

Hypoproteinemia (low serum blood protein)

Wednesday, March 8, 2017

Feline Hyperparathyroidism

Feline Primary Hyperparathyroidism

The little parathyroid glands play a big role in calcium regulation. 

            When it comes to glandular problems in the cat, the thyroid gets all the glory.   Hyperthyroidism in the most common feline endocrine disorder, and every cat-centric publication regularly features articles about it.  Adjacent to the thyroid gland, however, are four small glands called the parathyroid glands.  These little glands are immensely important in finely regulating the blood calcium level.

            There are two pairs of parathyroid glands in the cat, the external and the internal parathyroids.  The external glands are located external to the capsule that surrounds the nearby thyroid gland.  The internal parathyroids are actually embedded within the thyroid gland. 

The parathyroid glands produce a hormone called, not surprisingly, parathyroid hormone (PTH).  This hormone is the principal hormone involved in the precise, minute-to-minute regulation of the blood calcium concentration.  The goal of the body is to maintain the blood calcium level within a narrow range.  The parathyroid glands are exquisitely sensitive to changes in the calcium level, especially when the calcium level drops.  When this happens, the parathyroids release PTH.  This causes several complicated things to happen:

·      PTH causes the bones to release calcium (and phosphorus) into the blood stream.
·      PTH causes the kidney to produce increased amounts of an enzyme that promotes production of a hormone called calcitriol.  Calcitriol causes the intestines to absorb more calcium (and phosphorus) from the diet.
·      PTH causes the kidneys to absorb more calcium from the urine, (and excrete all that extra phosphorus that came from the bones and the intestinal tract.)

            The end result is the restoration of a normal calcium level.  When the calcium level returns to normal, it signals to the parathyroids “mission accomplished”, and tells them to reduce PTH secretion.

            Sometimes, the parathyroid glands produce too much PTH.  This condition is called, as you might imagine, hyperparathyroidism. Hyperparathyroidism exists in two forms, primary and secondary.  Secondary hyperparathyroidism can be further divided into nutritional secondary hyperparathyroidism (pretty rare) and renal secondary hyperparathyroidism (rather common).  The focus of this article in on primary hyperparathyroidism, as the complex physiology behind secondary hyperparathyroidism is probably beyond the scope of the typical cat owner.

            Primary hyperparathyroidism occurs as a result of one of the parathyroid glands secreting excessive amounts of PTH on its own.  The cause of the excessive secretion is usually due to a benign tumor of one of the glands, called an adenoma, although in rare instances, the tumor is a malignant carcinoma.   Affected cats tend to be older, the age range in reported cases being somewhere between 8 and 15 years of age. Clinical signs tend to be non-specific and include lethargy, poor appetite, and vomiting.   Physical examination of the cat tends to be unremarkable, the only consistent finding is the detection of the enlarged parathyroid gland in the neck in about 50% of the cases.  Routine blood tests show an elevated calcium level.  Because PTH causes the kidneys to excrete phosphorus, some cats with primary hyperparathyroidism will have low serum phosphorus levels. In some cats, the elevated calcium levels results in the formation of calcium oxalate stones in the bladder, and some cats will have sign related to this, such as increased frequency of urination, straining to urinate, urinating in inappropriate places, and blood in the urine. 

            Definitive diagnosis if primary hyperparathyroidism requires measurement of the serum level of PTH along with measurement of serum ionized calcium (iCa). Ionized calcium provides a more accurate assessment of the calcium status.   If the PTH level and the iCa level are both high, the diagnosis is obvious.  If the iCa is high and the PTH is in the upper half of the reference range, the cat probably still has hyperparathyroidism because when the calcium level is high, the proper response of the parathyroid gland is to shut down production of PTH.  A PTH level in the upper half of the reference range in the face of an elevated calcium is an inappropriate response and suggests that the parathyroid gland has gone haywire and is secreting the hormone autonomously.  A diagnosis is trickier when the iCa is high and the PTH level is in the lower half of the reference range.  There’s no real consensus on what is an appropriately low PTH level in the face of an elevated iCa.  Certainly, if the iCa is high and the PTH level is undetectable, then hyperparathyroidism is probably not the cause of the high calcium.  But a low normal PTH level in the face of high iCa is a diagnostic dilemma.  Ultrasound of the thyroid region of the neck may reveal a single enlarged parathyroid gland, which would be highly supportive of the diagnosis.  Not finding an enlarged gland, however, doesn’t rule it out. 
            The most commonly recommended treatment of primary hyperparathyroidism is parathyroidectomy – surgical removal of the abnormal gland.  Ultrasound of the neck helps identify the exact location of the tumor, i.e. whether it is one of the external parathyroids or the internal parathyroids.  This allows for proper pre-surgical planning.   Anesthetic complications related to elevated calcium levels include abnormally slow heart rate, high blood pressure, and cardiac arrhythmias, so careful anesthetic planning is a must.  At surgery, one large parathyroid gland is usually found.  As a result of that one gland producing such high amounts of PTH, the other three glands have shut off production of PTH completely, causing them to atrophy and making them impossible to identify.  A tumor of one of the external parathyroid glands is usually easy to identify (unless it is embedded in fat, making the identification a bit trickier).  Parathyroid tumors involving one of the internal parathyroids are harder for the surgeon to identify.  If an internal parathyroid is affected, removal of that entire lobe of the thyroid gland is required.  In dogs, a method of treatment called chemical ablation that involves the injection of ethanol into the abnormal gland has been described, however, studies of the effectiveness of this method of treatment in cats are lacking.

            Post-operative complications occur occasionally, the most common being, ironically, a low calcium level.  (This is a bigger problem in dogs than in cats.) As mentioned above, excessive production of PTH by a tumor in one parathyroid gland results in atrophy of the remaining parathyroid glands.  Removal of the offending gland will cause a rapid drop in blood PTH levels.  It takes a while (typically two to three weeks) before the remaining parathyroid glands “wake up” and start producing PTH again.  Until that happens, it is essential that the cat be monitored for clinical signs of hypocalcemia (low calcium).  Cats that experience low calcium post-operatively can be treated with a combination of calcium supplements and vitamin D. The supplementation can be tapered over a few weeks as the remaining parathyroid glands begin to function normally. 


Monday, February 27, 2017

Body Parts - The Pancreas

Body Parts: The Pancreas

They say that big things come in little packages, and nowhere is this more apparent than the feline pancreas.  This small organ, often weighing no more than 6 to 8 ounces, plays a huge, multifaceted role in maintaining your cat’s health. 

The pancreas is shaped like an upside down V.   The left lobe of the pancreas is nestled up against the stomach, while the right lobe runs alongside the duodenum (the first part of the small intestine).

The amazing thing about the pancreas is that it acts like two organs in one.  On the one hand, it is an endocrine organ, i.e., it produces essential hormones such as insulin and glucagon, which control the level of sugar in the blood.  These hormones are released from the pancreas directly into the bloodstream. The pancreas also functions as an exocrine organ, releasing enzymes into the small intestine that are essential for proper digestion of the proteins, fats, and carbohydrates found in food.  These enzymes are released through little ducts that open directly into the intestine, rather than into the bloodstream. 

The most common disorder involving the pancreas is diabetes.  It occurs as a result of inadequate or improper secretion of insulin.  Although any age cat may be affected, middle aged and older males are at increased risk. Obesity is a predisposing factor.  Interestingly, Burmese cats are four times more likely to be stricken with diabetes compared with domestic shorthaired cats.  The classic clinical signs of diabetes are excessive thirst (polydipsia), increased urination (polyuria), extremely good appetite (polyphagia), and weight loss. Some diabetic cats exhibit weakness in their rear legs, a condition called diabetic neuropathy.  The diagnosis is usually straightforward.  The presence of a high blood sugar in conjunction with sugar in the urine confirms the diagnosis.  Treatment of diabetes involves administering twice daily injections of insulin under the cat’s skin.  Diets that are high in protein and low in carbohydrates are also an important part of the management of diabetes.  In fact, a small percentage of diabetic cats can be managed solely with a change in diet.  Most cats, however, require insulin injections.  In some diabetic cats, early diagnosis and aggressive dietary and insulin therapy may cause the diabetes to resolve.

Pancreatitis (inflammation of the pancreas) is another common disorder. The clinical signs of pancreatitis vary widely and may include poor appetite, fever, vomiting, diarrhea, lethargy, and abdominal pain.  For years, veterinarians have grappled with diagnostic tests for pancreatitis.  The disorder cannot be diagnosed based on historical or clinical signs alone because the signs mimic many other diseases in cats.  Some cats with pancreatitis may have an elevated white blood cell count, a mildly elevated blood sugar, and a mildly decreased calcium level, but these findings are inconsistent and non-specific. X-rays are rarely helpful. Ultrasound is better, but is costly and results are subjective and highly dependent on the skill of the ultrasonographer. The lack of a simple, reliable blood test specifically for pancreatitis has caused the disorder to be under-diagnosed, or misdiagnosed entirely. Fortunately, the recent development of the feline pancreatic lipase immunoreactivity (fPLI) test has greatly increased our ability to diagnose this frustrating disorder.  Normal cats have low levels of fPLI circulating in their bloodstream.  Cats with pancreatitis typically show dramatic elevations of their fPLI levels. 

Treatment of pancreatitis is mainly supportive.  Intravenous fluid therapy is necessary to ensure that the pancreas is well perfused with blood.  If nausea or vomiting is present, the use of anti-nausea drugs is warranted.  Abdominal discomfort is a common component of pancreatitis, and the use of pain medication typically is part of the treatment plan.  Cats that won’t eat may require an appetite stimulant to promote proper nutrition.  The prognosis for cats with pancreatitis varies, although most cats do recover.

A less common pancreatic disorder in cats is exocrine pancreatic insufficiency (EPI).  In this disorder, the pancreas does not produce enough digestive enzymes.  Cats eat their food, but they can’t digest it, so they lose weight.  They often compensate by eating more, but to no avail.  Affected cats usually have greasy, foul-smelling diarrhea.   In dogs, EPI is usually a genetic condition, with German Shepherds being predisposed.  In cats, the genetic form is rare.  Feline EPI is usually a sequel to chronic pancreatitis.  Repeated bouts of pancreatitis result in scarring of the pancreas.  As scar tissue accumulates in the pancreas, the organ becomes less able to produce digestive enzymes, and cats develop EPI.  A blood test, the feline trypsin-like immunoreactivity test (fTLI) (not to be confused with the fPLI test) easily diagnoses the disorder.  If the fTLI test comes back low, the cat almost certainly has EPI.   Treatment, fortunately, is simple.  Pancreatic enzyme powder, added to the food, corrects the enzyme deficiency.  Cats will gain weight and the diarrhea will resolve.  Affected cats require supplementation for the remainder of their lives. 

Friday, February 17, 2017

Body Parts - The Lungs

Body Parts – The Lungs

In this post, I’m going to shout about the kitty lungs, because there’s a lot to shout about.  Feline lungs are remarkably similar to your own lungs.  For example, the lungs occupy most of the space in the chest cavity, lying on both sides of the heart, just like they do in humans. 

In my mind, I think of the lungs as being divided into two portions – the airways, and the lung tissue. An easy way to understand it is to imagine a tree in full bloom.   The trunk of the tree is like the trachea (windpipe).  Imagine the trunk goes up a bit, and then divides into two big branches.  Those are the main bronchi.  Those big branches give rise to smaller branches. Those are the bronchioles.  Those branches divide into smaller and smaller branches, which is exactly what happens to the bronchioles in the lungs.  Finally, think of the leaves that grow on all of the small branches as the lung tissue that surrounds the little bronchioles. Get the picture? The trunk, branches and twigs are the airways; the leaves are the lung tissue. 

You can break down the function of the lung into two main jobs:  ventilation and perfusion.  Ventilation is breathing – the movement of air in and out of the lungs.  Perfusion is the process by which the lung absorbs oxygen from the air into the blood stream and exchanges it for carbon dioxide, which is exhaled into the environment.  Most of the time, ventilation and perfusion are both happening correctly and simultaneously, allowing the blood to receive the proper amount of oxygen for delivery to the vital organs.

When something goes wrong with the lungs there could be an airway problem, which can affect ventilation, or a problem with the lung tissue itself, which can affect perfusion.  For example, a common lung disorder in cats is bronchitis.  Infectious bronchitis is due to an infection (usually bacterial) of the airways.  The infection causes impaired flow of air through the airways. This affects ventilation.  Asthma is a type of bronchitis caused by an allergy to something in the environment.  When a cat breathes in an allergen, it causes the airways to constrict.  It becomes harder for air to pass through these narrowed airways.  The cells lining the airways become irritated by the allergen, and they will produce mucus, which may plug the already narrowed airways.  Clearly, asthma affects ventilation.  Infectious bronchitis is treated with antibiotics.  Asthma is treated with anti-inflammatory drugs and drugs that dilate the airways, making it easier to breathe.  Of course, the best treatment for asthma would be to remove the offending allergen from the environment (cigarette smokers, take the hint), although identifying the allergen can be difficult.
An example of a problem with the lung tissue itself would be a bacterial infection of the lungs.  This is called pneumonia.  When the lung tissues get infected and the lung fills with pus, it prevents oxygen from being absorbed into the bloodstream and carbon dioxide from being removed.  Another condition affecting the lung tissue is pulmonary edema.  In this disorder, the lung fills with fluid, which impairs perfusion similar to the way pneumonia does.  Pulmonary edema usually occurs as a result of heart failure.  Pneumonia is treated with antibiotics.  Pulmonary edema is treated with diuretics – drugs designed to remove the fluid from the lungs.  If heart disease is the cause, medications to treat the heart are administered as well. 

How do we know that a cat is experiencing a lung problem?  A primary clinical sign of a lung problem is coughing.  Hey, wanna drive a veterinarian crazy?  Tell him that your cat is trying to “cough up a hairball”.  Hairballs come from the stomach.  Cats vomit up hairballs; they do not “cough” them up.  If your cat hunkers down, extends his neck, and makes several raspy throat-clearing sounds, he is coughing, and it is not a hairball.  It is likely asthma or bronchitis.  Another sign of lung disease is labored breathing.  The medical term for this is dyspnea (DISP-nee-uh).  If your cat is lying around relaxing, but his chest is moving as if he’s just done a few laps around the jogging track, there’s probably a lung issue going on.  He needs veterinary attention immediately.  Like, now. 

Here’s another way to drive your veterinarian batty: tell him your cat has been “wheezing”.   Wheezing is the sound of air trying to flow through narrowed airways in the lungs.  It’s something you hear when you put a stethoscope up to a cat’s chest.  When I’m told a cat is wheezing, I instinctively think “lung problem”.   When a cat owner says “wheezing”, they probably mean stertor, which is noisy breathing that occurs during inhalation.  It’s a low-pitched sound. In other words, your cat is snoring.  This is not a lung problem.  Another possibility that the cat has a blockage of the nasal passages (simply put, a stuffy nose), resulting in high pitched, noisy breathing.  This is called stridor.  Because wheezing usually means lung disease and lung disease is sometimes an emergency, don’t say your cat is wheezing.  It freaks us out.  Say your cat is congested or has noisy breathing instead.  I (and thousands of veterinarians) thank you.

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