Sunday, October 30, 2016

Chronic Rhinosinusitis in Cats

Chronic Rhinosinusitis in Cats

Chronic infection and inflammation of the nasal cavity and sinuses is a frustrating problem for cats, their owners, and the veterinarian.

            Upper respiratory infections are very common in cats, especially kittens.   Most of these infections are caused by viruses.  Approximately 90% of all upper airway infections in cats are caused by two common viruses:  feline herpesvirus and feline calicivirus.  Some affected cats develop secondary bacterial infections, which can make treatment and recovery longer and more difficult. 

 Acute sinusitis tends to affect young kittens and often causes sneezing, discharge from the eyes, a snotty nose, decreased appetite, lethargy, and usually a fever.  If oral ulcers are present, calicivirus is likely playing a role.  If corneal ulcers are present, the herpesvirus is most likely.  Many cat owners report a change in their cat’s meow, i.e. sounding more hoarse or even silent, or that the purr sounds more raspy. Treatment tends to be based on clinical signs.  Cats with conjunctivitis as a result of their viral infection often require antibiotic eye drops or ointments.  Secondary bacterial infections are treated with oral antibiotics.  Appetite stimulants may be warranted in cats that won’t eat.  Most of these acute infections are self-limiting, and cats usually recover uneventfully.

            Some cats, however, do not recover uneventfully.  Sever viral infection can result in permanent damage to the delicate anatomy in the nasal cavity, which predisposes the cat to recurrent bacterial infections.  Complicating matters, the feline herpesvirus is notorious for taking up permanent residence in the cat’s body.  The virus can periodically emerge from its dormant state, causing a flare-up of clinical signs and further destruction of the fragile turbinate bones in the nasal cavity.  These cats are said to have chronic rhinosinusitis.

            Chronic rhinosinusitis affects cats of any age.  The main clinical signs are intermittent or persistent sneezing, nasal discharge (either unilateral or bilateral), and congested breathing.  Discharge from the eyes is usually not present (although it can be, occasionally), and in general, these cats tend to not be systemically ill. Most veterinarians prescribe a short course (7 to 10 days) of antibiotics in cats with upper respiratory disease, and the fact that cats on antibiotics usually show clinical improvement supports their use.  However, clinical signs often recur despite therapy, which implies that bacteria are only one factor in feline upper respiratory disease.  If a 7 to 10 day course of antibiotics fails to resolve the disease, a thorough diagnostic work-up should be pursued before settling on a diagnosis of chronic rhinosinusitis.

            Although the most common cause of chronic rhinosinusitis is a prior, severe herpesvirus infection with subsequent damage to the nasal cavity, a diagnostic workup should be undertaken to rule out potentially treatable conditions, such as fungal infection, cancer, polyps, oronasal fistulas (a physical communication between the mouth and the nasal cavity) and foreign bodies.  This work-up may include bloodwork, a blood test to look for Cryptococcus (the most common fungus affecting the upper respiratory tract in cats), a thorough oral/dental examination, rhinoscopy (visualization of the inside of the nasal cavity and the back of the throat using a rhinoscope, an instrument that can be inserted directly into the nostrils), and a CT scan.  Radiographs may be helpful, but CT scans are preferred as the images they generate are thin, cross-sectional slices of the entire nasal cavity.  If rhinoscopy is performed, biopsy specimens should be submitted for histopathology to rule out cancer, and samples should be obtained for bacterial culture.  If the diagnostic tests rule out the treatable disorders mentioned above, then the diagnosis of idiopathic (i.e. no known cause) chronic rhinosinusitis is confirmed.  Now comes the hard part: trying to manage the disease and keep the cat comfortable.

            Veterinarians often choose antibiotics to treat cats with upper respiratory disease, whether to treat a secondary bacterial infection that is concurrently infecting the cat, or to prevent one from developing. If bacterial culture grows a single organism that isn’t typically found as part of the normal nasal flora, then an antibiotic should be chosen based on the proven effectiveness against that organism, and it should be administered for 6 to 8 weeks.  If multiple organisms are grown on culture, the significance of this questionable, since there are many species of bacteria that normally inhabit the nasal cavity.

            Antifungal drugs aren’t prescribed to treat chronic rhinosinusitis unless a fungal organism is proven to be present.  This is fairly uncommon occurrence.

            If an allergic component is suspected (i.e. the symptoms seem to be somewhat seasonal), antihistamines may be considered. 

            Obviously, if a polyp is diagnosed via rhinoscopy, the polyp should be removed surgically.  If cancer is diagnosed, treatment options can be offered.  The prognosis varies considerably depending on the type and extent of the cancer. 

            Because the herpesvirus is considered to be the main culprit in initiating and perpetuating chronic rhinosinusitis in cats, treatment directed at the virus itself may be beneficial.  Administration of an intranasal herpesvirus and calicivirus vaccine two or three times a year may help to stimulate a local immune response within the nasal cavity.  Oral antiviral drugs, such as famciclovir, have been administered to cats with confirmed herpesvirus infections, with promising results.  The amino acid lysine has been used to reduce the frequency of herpesvirus reactivation in infected cats, however, recent controlled studies are casting doubt on the efficacy of lysine. 

            Anti-inflammatory drugs play a role in the treatment of chronically affected cats.  They reduce airway swelling, improving breathing and making the cat more comfortable.  Glucocorticoids are the most commonly prescribed drug for this, with prednisolone being the drug of choice.   Because these drugs can suppress the immune system, there is concern that the respiratory infection could potentially worsen if these drugs are used continuously over the long term.  Thus, glucocorticoids are best used intermittently.  For example, using prednisolone daily for a week, and then tapering the dosage to every other day for an additional week, would be a reasonable schedule. 

            Supportive care, such as maintaining hydration (to keep nasal secretions less viscous and easier to clear), humidifying the air (for example, isolating the cat in a bathroom while running a hot shower, allowing the cat to breathe in the steamy air), and ensuring proper nutrition (for example, using appetite stimulants such as mirtazapine in affected cats that are eating poorly) are helpful in keeping affected cats happy and comfortable. 

            Cats with chronic rhinosinusitis will never be cured, however, with medical management and supportive care, most cats can have their sneezing and nasal discharge kept to a minimum, and maintain an excellent quality of life.



Wednesday, October 19, 2016

Halitosis in Cats

Halitosis in Cats

            Cats are well known for being exceptionally clean animals.  They take pride in their appearance, grooming constantly to remove any offensive odors that might make them detectable to both predators and prey.  Occasionally, however, cats do emit a foul odor.  Although there are several possible reasons for a cat to be malodorous, as a cats-only veterinary practitioner, I find that halitosis, i.e bad breath, is the most common cause of fetid felines.

 Periodontal disease – inflammation of the tissues surrounding the teeth – is by far the most common cause of stinky breath in cats.    Periodontal disease is initiated by a build-up of plaque, the sticky bacteria-laden coating on the tooth surface. As the immune system responds to the plaque, the gums become inflamed.  Gum inflammation is called gingivitis, and is the first stage of periodontal disease.  Bad breath often accompanies the gingivitis. As inflammation progresses, the second phase of periodontal disease – periodontitis – occurs.  Periodontitis is a condition where both the soft tissues and the bony tissues are affected.  Cats may develop receding gums, bone loss, and continuing halitosis.  If not removed from the tooth, plaque mineralizes into tartar (also called calculus) in a few days.  Calculus requires professional removal by your veterinarian. 

            Although periodontal disease and gingivitis tend to develop as cats age, gingivitis can occur in cats as young as 6 months.  These cats often have little or no calculus accumulation.  We call this condition “juvenile-onset gingivitis”, and it is a common cause of halitosis in kittens.  The exact cause of this condition is unknown, but genetics is suspected to play a role, since purebred cats, especially Abyssinians, Siamese, and Persians are predisposed.  If left untreated, these cats may develop significant periodontal disease early in their adulthood.  Daily home oral care is recommended in cats with juvenile-onset gingivitis to avoid future dental problems.

            Infections or abscesses can cause foul odors from the mouth.  Tooth-root abscesses are common in cats, usually resulting in facial swelling near the site of the affected tooth.  Tooth-root abscesses need to be lanced and drained by your veterinarian, and the affected tooth is likely to require extraction.

            Ulcers in the mouth can result in halitosis.  The calici virus is a common cause of feline upper respiratory infections.  Although sneezing, runny eyes, and a snotty nose may be seen in affected cats, an ulcer on the tongue is the classic finding in cats infected with calici virus. 

            Sadly, tumors of the oral cavity are not uncommon in cats, and halitosis is a frequent accompanying symptom.  The most common feline oral tumors are squamous cell carcinoma and fibrosarcoma.  As these tumors grow, a portion of the tumor may become infected or necrotic (non-viable), leading to an unpleasant smell from the mouth.  Early detection and aggressive treatment are essential for therapy to be successful.  Unfortunately, by the time most cats are showing clinical signs of their oral tumor, the condition has already progressed to a point where treatment isn’t possible. 

            Disorders of oral origin aren’t the only cause of halitosis in cats.  Systemic illnesses, such as kidney disease, can lead to bad breath in cats.  The role of the kidneys is to filter toxins from the bloodstream, creating urine in the process.  As most cats age, they eventually begin to show signs that their kidneys are weakening.  These signs may include excessive thirst, increased urination, poor appetite, weight loss, and vomiting.  As the kidney dysfunction progresses, cats may develop a condition called uremia, literally “urine in the blood”.  Uremia generally refers to cats with severely elevated toxins in their bloodstream.   Uremia results in a characteristically foul odor from the mouth.  The smell differs from the bad smell caused by dental disease.  As one of my colleagues once indelicately put it, cats with uremic breath smell like “something died inside their mouth.”   A crude description, but I can attest to its accuracy.   Cats with severe uremia will sometimes develop ulcers in their mouths, often on the sides of the tongue.  These ulcers contribute further to the halitosis.

            Diabetes is a common glandular disorder in cats due to inadequate or improper secretion of the hormone insulin from the pancreas.  Insulin is required for the utilization of glucose, which is the primary source of energy in cats.  Cats with diabetes usually require twice daily injections of insulin to maintain proper blood glucose levels.  If the diabetes remains undiagnosed or untreated, cats will metabolize body fat into molecules called ketones, in a desperate attempt to provide energy to the body.  Ketosis is a veterinary emergency, and affected cats are usually very ill.  Cats in ketosis have a characteristic smell to their breath.  The odor has been described by some as being “fruity”, and by others as faintly resembling acetone, the main ingredient in nail polish remover.  Whether ketone-breath qualifies as being offensive, like halitosis, is debatable.  Interestingly, people vary in their ability to detect this smell in cats, and apparently, the ability to detect it is genetic.  Some people have the gene that allows them to detect ketones instantly, while others are oblivious.  Sadly, I cannot detect it.  A doctor who worked for me a few years ago could smell it a mile away. 

 And finally, it should be said that halitosis is sometimes in the nose of the beholder.  I have examined many cats brought into my office with the complaint of bad breath and upon examination, the cats were discovered simply to have, for lack of a better term, “kitty fish-breath”.  Their mouths were normal – no dental disease, no oral pathology of any kind – and they had no systemic illness.  Cat owners must simply realize that if you feed your cat stinky food, it may end up with stinky breath.  However, because there are so many significant medical conditions that can lead to halitosis in cats, it’s best to err on the side of caution and have any offensive oral odors evaluated by a veterinarian. 

Saturday, October 8, 2016

The Lymph Nodes - What Are They, and What Do They Do?

Body Parts – the Lymph Nodes

I’m sure you’ve heard of them, but do you really know what they are, or what they do?  I’m talking about the lymph nodes, important structures that we don’t think about much, but play a crucial role in a cat’s ability to fight off infections.

Lymph nodes are small, oval shaped organs that are dispersed throughout the body.  They are a part of the lymphatic system, a branch of the immune system that plays an important role in the development of the body’s immune response.  The lymphatic system consists of vessels that run throughout the body, in a similar fashion as arteries and veins.  Instead of blood, however, the fluid that flows through the lymphatic system is called lymph, which is rich in protein and white blood cells.  Cells of the immune system circulate throughout the lymphatic vessels in the body.  As lymph flows through these vessels, it passes through at least one set of lymph nodes, and often several sets, before ultimately emptying into the general circulation, where it mixes with blood.  The lymph nodes are the major sites in the lymphatic system where the immune cells gather.

The main job of the feline immune system is to protect and defend the body against harm by fighting off invading substances, which we call antigens.  When an antigen invades the body, it eventually encounters the lymphatic system, and eventually a lymph node.  Here, it stimulates a discrete population of lymphocytes (a type of white blood cell) in the node.  This causes those lymphocytes to multiply and transform, or become “activated”.  These activated lymphocytes mount an immune response to the antigen, for example, by producing antibodies that neutralize the antigen.  When the lymphocytes in the lymph node multiply, the lymph node becomes enlarged.   The medical term for enlargement of the lymph node is lymphadenopathy.  Us humans usually refer to this as “swollen glands”.   As a veterinarian, I perform hundreds of physical examinations every year.  Every veterinarian performs a physical examination in his or her own style, making sure to evaluate all of the body systems.  Assessment of the size of the lymph nodes is unquestionably a part of every veterinarian’s physical assessment.

Enlargement of the lymph nodes is often discovered as an incidental finding during physical examination of the cat.  Now and then, a cat owner brings the cat to the vet because of symptoms related to lymph node enlargement, for example, difficulty swallowing due to enlargement of the lymph nodes in the back of the throat.  Sometimes a cat owner will bring me their cat because they detected a lump, which turns out to be a lymph node, while patting or stroking the cat.

The age of the cat is important when considering the significance of lymph node enlargement.  Kittens and young cats are exposed to a variety of antigens early in their lives, and an increase in lymph node size is an expected response by the immune system.  As cats mature, lymph node size usually decreases and the nodes often become more difficult to feel in older animals.  However, in geriatric cats or cats that have lost weight due to illness, the loss of body fat around the lymph nodes may make the lymph nodes appear more prominent than expected, and are easier to feel.

As noted above, stimulation of the immune system by invading antigens is a common cause of lymph node enlargement.  Sadly, cancer is an equally common cause.  The cancer can arise from the lymph node itself.  This is called lymphoma, and is the most common cancer found in animals.  Cancer arising in other parts of the body can also spread to the lymph nodes.  This is called metastatic cancer, and the cancer is said to have “metastasized” to the lymph nodes. 

Figuring out the cause of lymph node enlargement may require a variety of tests, including blood and urine analysis, x-rays, and ultrasound.  Ultimately, a definitive diagnosis often requires obtaining a sample of cells from the node itself.  This is usually achieved either by aspiration cytology or by surgical biopsy. Aspiration cytology is a procedure in which a needle, attached to a syringe, is inserted into the lymph node.  Suction is applied to the syringe so that cells from the lymph node are sucked or “aspirated” into the hub of the needle.  The contents are then sprayed onto a microscope slide and are sent to a laboratory for interpretation.  The advantage of this procedure is that it’s non-invasive and inexpensive.  A disadvantage is that the aspirate may not yield enough cells to make a diagnosis. Biopsy of the lymph node is the definitive test in evaluating lymph node enlargement.  Depending on the size and location of the node, either the entire node is removed (this is called “excisional biopsy”), or a small piece of the lymph node is removed (“incisional biopsy”).  The specimen is evaluated by a pathologist.  Treatment is based on the biopsy results: infections are usually treated with antibiotics; cancer is treated by chemotherapy, surgery, radiation, or a combination of these.

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