Treatment Explanation


Treatment for Hyperthyroidism in cats:

There are three options for treatment of hyperthyroidism. All three are identical treatment forms to those for human patients with hyperthyroidism.

Oral anti-thyroid medications

    This medication (methimazole) blocks the production of thyroid hormones by the thyroid gland. This oral medication does not cure hyperthyroidism, and is usually required twice daily (lifelong) to control the disease. Methimazole can be useful in the treatment of hyperthyroidism in cats but it is not an innocuous drug. Regularly scheduled blood tests are required to adjust dosages and to determine if potentially harmful side effects are present. Owners frequently find that oral administration of this drug to their cat is costly and difficult over time.


    Surgical removal of the thyroid tumor (s) is performed under general anesthesia. This procedure usually results in a return to normal thyroid function for the cat though the risk of anesthesia must be given careful consideration. If both lobes of the thyroid gland are not removed, approximately 70% of cats will eventually develop a functional benign tumor of the remaining tissue, requiring additional treatment or surgery.

    Alternatively, removing both thyroid lobes during the same surgery increases the risks of disturbing calcium metabolism, which is governed by the 4 small, adjacent parathyroid glands. Because affected patients are usually geriatric, and under-conditioned, they must be monitored for post-surgical side effects including low calcium levels (hypocalcemia), and kidney dysfunction. They are commonly hospitalized from 2-5 days. To lessen anesthetic and surgical risk to the patient, a cat may be required to undergo medical therapy with methimazole until physical condition improves. Occasionally, hyperthyroid cats are found to have functioning thyroid tumors in the chest cavity, where surgery is not feasible.

Radioiodine I-131

    Of the three treatment options, radioiodine is considered by many to be the treatment of choice for most hyperthyroid cats. Overall, radioiodine provides a simple, effective, and safe cure for cats with hyperthyroidism. This form of therapy has been used successfully for over 50 years in human medicine, and over 20 years in veterinary medicine. It requires no anesthesia and can be offered to medically stable patients, regardless of their age!

    How does it Work?

    Thyroid function requires the uptake of the element iodine in the body in order to produce normal thyroid hormones. If a radioactive form (I-131) of iodine is administered to hyperthyroid cats, it accumulates in thyroid tissue wherever it occurs in the body. Thyroid tumors accumulate the greatest amount of radioactive iodine. Once inside the tissue, the radioactive iodine emits radiation, which destroys the overactive thyroid cells.

    The radioactive iodine not trapped in the thyroid is excreted in the urine and to some degree in the feces. The amount of radioactivity emitted by the compound naturally decreases by half, every 8 days. Thus, the radioactivity remaining in the cat's thyroid tumor tissue will painlessly dissipate on its own. Normal thyroid tissue tends to be automatically protected from the effects of radioiodine since the uninvolved thyroid tissue is suppressed and receives only a small dose of radiation. As an added patient benefit, there is no injury risk to the adjacent parathyroid glands. The residual (normal) thyroid tissue resumes full function within 1-3 months after treatment. An average of 95-98% of I-131 treated cats are permanently and safely cured with a single injection!

    Is it Safe?

    "Radioactive" iodine, despite its somewhat scary title, is considered the "gold standard" for safety and efficacy in treating hyperthyroid cats. I-131 administration is a safe and effective treatment for feline hyperthyroidism. This therapy has been successful in large numbers of cats, and the only recognized deleterious side effect has been hypothyroidism (underactive thyroid gland). This occurs in an extremely small percentage of cats and almost never requires specific treatment. The greatest risks are to the doctors and staff who work in the thyroid unit on a long-term basis. However, with stringent safety regulations, protocols, and monitoring, this form of therapy can be safe for cats and the caregivers!

Radiotherapy: What happens to my cat?

On or before the day of admission, you and your cat will meet with a veterinary medical specialist at PVESC. Your cat will be thoroughly examined and the medical records will be reviewed. The doctor will discuss any admission tests required (which can be done at your general veterinary hospital or on-site at PVESC prior to treatment) to ensure that radioiodine therapy is the best option for your cat. The results of any tests performed at PVESC will be discussed with you before proceeding with treatment. These tests can include:

    * A complete blood count

    * A thyroid hormone level (T4 or free T4) to an outside lab

    * Serum biochemistry analysis

    * Urinalysis

    * Blood pressure

    * Full body radiograph

    * Cardiac Pro BNP test

    * Ultrasonography (cardiac ultrasound to evaluate function if needed)

If your cat is judged to be medically stable, he or she will be admitted to the radiotherapy unit within 24-48 hours of your appointment. The unit is specially constructed for this use and houses only cats that are receiving radioactive iodine.

The quiet accommodations include "Southwest" decor and housing in roomy and cheery cat condos (by Snyder Manufacturing, Inc.). These condos have separate bathrooms and shelves for snoozing. The unit includes windows for natural lighting, music, and heated floors. The patients enjoy watching patrons of our bird and squirrel feeders.

Once the dose of radioactive iodine for your cat has been determined, it is injected painlessly under the skin (subcutaneous) exactly like a routine vaccination.

From that point on, your cat need do nothing else but sleep, eat and play while the radiation dissipates to safe levels (usually 3-7 days). We like to spoil all our patients as much as safely permissible. This brief separation is likely to be harder for the owners than the patients!

Your cat will be monitored daily while in our care. By daily monitoring of your cat's radiation level, we can determine when this level has declined to that allowable by law. At this time, your cat can be released to you. You will be contacted daily with updates during your cat's stay in the radiotherapy unit. If you have questions or concerns, do not hesitate to call us.


Admission Information


   1. You or your referring veterinarian may request an admission appointment.

   2. Anti-thyroid drugs (Tapazole, Methimazole, etc.) Should be discontinued 1-2 weeks prior to admission. Most other medications are allowable but should be discussed prior to the admission process.

   3. Food containing fish products should be discontinued 2 weeks prior to admission. Fish products have been found to prohibit the uptake of radioactive iodine.

   4. You are welcomed and encouraged to bring your cat's favorite foods and/or treats. We provide an ample, tasty feline menu as well.

   5. Cat toys may be kept with your cat but they cannot be returned.

   6. Unfortunately, the State of Maine, in accordance with the strict regulatory guidelines of the Nuclear Regulatory Commission cannot permit client visitation while cats are in the radiotherapy unit.

   7. Once admitted and treated with I-131, your cat cannot be released to you until his or her radioactivity levels drop to a specific range. In the extremely unlikely event that a patient dies from another illness while being housed in the I-131 unit, the remains must be held by us until radioactivity diminishes (eighty days).


Radioiodine therapy is considered the optimal treatment for cats with hyperthyroidism. It has an extremely high success rate and safety record and we are pleased to offer this state-of-the-art treatment.

The costs of therapy reflect costs associated with providing these services:

   1. Pre-admission consultation with a veterinary medical specialist

   2. Cost and administration of the radioactive iodine

   3. Hospitalization and patient care in the radiotherapy unit

   4. Litter, food, and patient monitoring with radiation monitoring equipment according to stringent state nuclear medicine regulatory guidelines

   5. Time and expertise of the staff

   6. Costs associated with nuclear regulatory licensing and adherence to strict safety guidelines for hospital personnel

   7. Radioactive waste-removal

The cost for treatment is $1500.00.  Pre-admission diagnostic tests are associated with separate fees.  These diagnostics may be completed at your primary care veterinary office or at PVESC and include such tests as radiographs, blood work (CBC Chemistry Electrolyte panel, T4, SDMA test), urinalysis and blood pressure.  Other tests, such as echocardiogram, may be recommended.  In the rare instance that your cat will require an increased dose of therapy, there will be an extra fee of $250.00 for cats that require more than 4 mCi of radioactive iodine for treatment due to the extra expense of the therapy and the extra hospitalization that is required. 


Discharge Instructions

Discharge instructions for owners of radiotherapy-treated cats:

For the first two weeks please follow these detailed home instructions for handling your cat and litter waste.

Please note that if you cannot or will not follow these instructions, you must notify us, and we may need to keep your cat hospitalized for additional time before release (additional fees apply).

The thyroid hormone level continues to decline for 30 to 60 days after treatment. During this time, the symptoms of hyperthyroidism are expected to abate. Gradual weight gain and return to healthy body condition are expected. If your cat is showing signs of illness or depression, please contact PVESC.

Upon discharge from PVESC (after an average of 4 to 7 days after treatment), treated cats will still be excreting radioiodine in their urine, saliva and feces. This radioiodine is in a form that can be taken up by the human thyroid where it may cause damage. Even through the level of radioactivity is much lower than the level at which human patients are released from the hospital, you must exercise caution during this period. The remaining radioactivity will be gradually eliminated from the cat over the next 2 to 4 weeks.

1. Treated cats must remain indoors only for two weeks after discharge.

2. Pregnant women, children under eighteen and people with immune mediated diseases should not have any contact with the cat or litter pan for two weeks.

3. Prolonged close contact with your cat (under 3 to 6 feet) must be avoided during this time. Limit visits to 20 minutes per session. Visit and pet your cat briefly, but do not allow the cat to sleep on your bed with you. Avoid contact with urine and saliva and do not allow the cat to sleep on your bedding.

4. Foods containing fish products can be reinstituted post-treatment.

5. Use disposable litter pan liners and plastic gloves to minimize handling of litter/waste.

6. Wash your hands after handling your cat, its food dishes and litter pan.

7. There is no need to quarantine your cat from other pets in the household.

8. If your cat must be seen by a veterinarian before the end of the 2-week quarantine, please alert PVESC.

While the amount of radioactive material remaining in your cat’s body is low, it is prudent to follow the above instructions exactly. If this is not possible, please consider boarding your cat with PVESC during the quarantine period (additional fees apply).

Waste Disposal

Disposal of litter pan contents:

If your home is on a public sewer system:

  1. Use scoopable/flushable litter such a “World’s Best Cat Litter” or Swheat”

  2. Wear protective gloves (such as dishwashing gloves), scoop your litter pan twice per day and flush the waste down the toilet.

  3. At the end of the two-week quarantine, flush all remaining litter down the toilet. The litter pan and scoop can be washed with soapy water and flushed down the toilet; it’s not necessary to save these items for any extended period or to discard them.

  4. This is the approved method of the State of Nuclear Regulatory Commissions.

If your home has a private septic system or if you have a public sewer and choose not to flush it:

  1. Your cat’s litter box must be scooped twice per day.

  2. Wear protective gloves (such as dishwashing gloves) and place the waste in a Ziploc or tie bag, be sure to double-bag the litter and excretions, then place the bag in a plastic tote with a locking lid that has been lined with a large garbage bag. This tote should be stored outside and away from small children, other pets and wild animals.

  3. At the end of the two-week quarantine, add all of the remaining litter from the boxes to the trash bag in the outside tote, tie the bag and leave all waste until the 80-day mark on your calendar.

  4. The litter pan and scoop can be stored with the trash bag in the tote for 80 days. It can then either be thrown out or washed and reused.

  5. When it is time to discard the waste, simply remove the large garbage bag from the tote and dispose of it as you would your household trash. The tote itself may be disposed of separately or can be rinsed out and reused.

Follow Up

We would like to recheck your cat’s progress in 4 to 6 weeks. This includes a physical examination, thyroid level (T4), renal panel with SDMA, electrolytes and body weight. If you prefer to see your primary care veterinarian for this, please have the results forwarded to PVESC.

Waste Disposal

Disposal of Litter Pan Contents
If your home is on public sewer use flushable litter. To dispose of your cat's urine and feces during its first 2 weeks post-treatment, scoop the soiled litter daily and flush it down the toilet. This is the approved method of the State of Nuclear Regulatory Commissions. If you refuse to follow this method or, your home has a private septic system, you must take these steps:

   1. For the first 14 days after your cat returns home from receiving I-131 therapy, put on your gloves, use your litter scoop to drop all soiled litter into a Ziploc (or similar) bag. Zip it shut. Place this bag in the second Ziploc (or similar) bag and zip it shut.

   2. Place the double-bagged litter, feces and urine in a large Tupperware (or similar) type container, lined with a trash bag, and close it with a tightly locking lid.

   3. Follow this process for 14 days, placing all double-bagged litter, feces and urine in the Tupperware (or similar) container, and lock the lid after each addition to the container.

   4. Mark on your calendar 94 days after the date of discharge from our facility for the stored litter to be discarded.

   5. During the time you store the container, place it outside where it cannot be reached by small children, pets, wild animals, etc, or in a basement or garage. Do not place it in occupied areas.

   6. At the end of the second week, put on your gloves and, in one step, pick up the edges of the litter liner containing any remaining litter, tie them together and place it with the litter you have collected over the previous two weeks. Dispose of your gloves, and wash or dispose of your litter scoop in the outside trash. If you have been unable to successfully use a litter pan liner, dispose of your litter pan as well. You may now return to your normal litter disposal routine.

   7. 94 days after discharge from our facility, open the container, pick up the trash bag lining it, and place the bag in your outside trash. Do not bury the litter or use it in the garden. You may dispose of the container separately.

Patient Follow-up

What will Treatment be like for my cat?

The ideal goal of 1-131 therapy is to restore normal thyroid function with a single dose of radiation without permanently damaging normal thyroid tissue. Most hyperthyroid cats treated with 1-131 are cured by a single injection-No surgery! No anesthesia! No medication!

Successful treatment results in normal thyroid hormone levels within 2 weeks of treatment in 70-8O% of cats. Over 90% of treated cats reach normal hormone levels within 3 months post-treatment. Cats often feel better within days of treatment and most owners can expect gradual and steady health recovery within 2 months.


Medical Follow-up

Copies of all pertinent medical records and test results regarding your cat's treatment will be forwarded to your primary care veterinarian. We recommend a recheck examination, thyroid (T4) level and kidney (renal) profile with your veterinarian 2-3 months after I-131 treatment. Please have the results forwarded to PVESC.

Limbal Melanomas

By: Rachel Mathes, DVM, MS, Diplomate ACVO

Facts about Limbal Melanomas:

  • Benign, slow growing tumors in dogs and cats
  • Very responsive to a variety of therapies
  • Low rate of metastasis
  • Low rate of recurrence with treatment
  • Early referral recommended

Limbal melanomas are benign, slowly growing tumors of limbal melanocytic origin. These tumors typically occur along the dorsomedial to ventrolateral limbal arc of the globe at the corneal and scleral junction.1 A bimodal age distribution has been described with a peak occurrence at 3-4yrs of age and 7-10yrs of age in dogs (1,2). These tumors are thought to have an inherited basis as Golden Retrievers are four times more likely and Labradors are three times more likely to develop this compared to other breeds (1). Though benign, limbal melanomas may become globe-threatening with growth due to local invasion. Often, secondary keratitis with corneal lipid deposition will occur as a result of the tumor presence (2,3).  While these tumors are less common in cats, they may occur and have a similar clinical course as canine melanomas (3).  Feline and canine limbal melanomas are amenable to a variety of therapies including surgical debulking with a combined keratectomy and sclerectomy, cryotherapy, laser photocoagulation, radiation and surgery with homologous and autologous grafting (2,3,4). In one recent study, only 1 our of 30 tumors recurred after a combination therapy protocol (2). In addition, the incidence of side effects from surgery was low with less than 10% of complications being potentially globe threatening (2).  After laser photocoagulation, a low recurrence was reported with 1 out of 15 masses recurring at 3 months and 2 out of 15 recurring at one year. Twelve of the fifteen tumors did not recur (3). 

Long term control and vision are attainable and reasonable goals with appropriate therapy. Early referral is recommended to preserve vision and globe integrity.

A dorsomedial limbal melanoma in the left eye is pictured. The mass is heavily pigmented, raised, irregular and well-demarcated with an arc of white corneal lipid at the leading edge.


Dr. Rachel Mathes, DVM, MS, Diplomate ACVO

 Facts about Glaucoma

• Secondary glaucoma more common than primary glaucoma

• Females overrepresented 2:1 for primary glaucoma

• Primary glaucoma typically associated with iridocorneal angle closure and increased intraocular pressure during middle age (6-8 years old)

• Canine glaucoma tends to be aggressive

• Feline glaucoma is almost exclusively secondary

• Concurrent institution of prophylactic therapy for the contralateral eye should be instituted if an eye is enucleated for primary glaucoma

• Imperative to address IOP spikes immediately as they may quickly cause complete blindness

Glaucoma is a term used to describe a group of diseases that cause elevated, often severely, intraocular pressure. This condition is very painful and treatment is aimed not only at preservation of vision, but also for pain management. The pain of glaucoma may be referred pain (migrane headache) and patients may exhibit discomfort by decreased activity, increased sleeping or subtle changes in behavior.1 The signs of pain may not even be noted by the owner until the discomfort is treated, at which time the patient may be noted to return to normal activity or “act like themselves again.” Primary, or breed related, glaucoma in dogs is most commonly due to closure of the aqueous drainage angle or Primary Angle Closure Glaucoma (PACG).1 Females are approximately twice as likely to develop PACG compared to males.2 PACG has different features for different canine breeds, however, the end result is failure of normal aqueous outflow, causing significant intraocular pressure elevation. Acute primary glaucoma may often be treated medically or surgically if addressed immediately, even if there is vision loss at the time of increased intraocular pressure.1,3,4 Chronic primary glaucoma causes extensive intraocular damage and blindness. Therapy is aimed at preventing intraocular pressure spikes, decreasing intraocular pressure and maintaining functional vision.4-7 This therapeutic goal is rarely achieved long term with medication alone and surgical intervention is almost always necessary.5 To preserve functional vision, glaucoma surgery is usually recommended early in the disease course due to the aggressive nature of this disease. Typical surgeries performed include laser cyclophotocoagulation (ciliary body destruction) and anterior chamber valve placement.5 The combination of these surgeries resulted in good control of the intraocular pressure in 76% of cases.5 In cases of irreversibly blind globes, more permanent salvage procedures are recommended as glaucoma is painful (enucleation or an intrascleral prosthesis).

Secondary glaucoma results from other underlying ocular pathology. The most common causes are lens luxations (most often seen in Terrier breeds), uveitis and cataracts. Treatment is aimed at reducing the intraocular pressure and addressing the underlying cause of pressure elevation. Topical glaucoma therapy should be limited, in cases of secondary glaucoma, to medications that do not exacerbate pre-existing ocular disease. Topical carbonic anhydrase inhibitors (e.g. dorzolamide, brinzolamide) or topical beta blockers (e.g. timolol) are recommended for primary or secondary glaucoma. Prostaglandin analogs (e.g. latanoprost, travaprost), while often the first line of therapy for primary glaucoma, should be avoided for secondary glaucoma therapy as they may exacerbate pre-existing ocular disease.


          Image ( A )

         Image ( A )

                   Image ( B )

                   Image ( B )


A patient with acute glaucoma is depicted (A). Note the severe scleral injection and corneal edema. Acute glaucoma must be addressed immediately in order to preserve vision and treat patient discomfort. A patient with chronic glaucoma is depicted (B) Note the significant buphthalmos (globe enlargement), scleral injection and corneal edema. This eye is irreversibly blind, but is quite painful. Therapy is aimed at providing long term patient comfort. Prophylactic therapy should always be instituted in the contralateral eye if an eye is removed for intractable, primary glaucoma.


1. Reinstein S, et al. Canine glaucoma: pathophysiology and diagnosis. Compend Contin Educ Vet. 2009:10;450-2.

2. Tsai S, et al. Gender differences in iridocorneal angle morphology: a potential explanation for the female predisposition to primary angle closure glaucoma in dogs. Vet Ophthalmol. 2012:15S1;60-3.

3. Scott E, et al. Early histopathologic changes in the retina and optic nerve in canine primary angle-closure glaucoma. Vet Ophthalmol. 2013:16S1;79-86.

4. Dees D, et al. Efficacy of prophylactic antiglaucoma and anti-inflammatory medications in canine primary angle-closure glaucoma: a multicenter retrospective study (2004-2012). Vet Ophthalmol. 2013:5.

5. Sapienza J, et al. Combined transscleral diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs with primary glaucoma: 51 cases (1996-2004). Vet Ophthalmol. 2005:8:121-7.

6. Miller P, et al. The efficacy of topical prophylactic antiglaucoma therapy in primary closed angle glaucoma in dogs: a multicenter clinical trial. J Am Anim Hosp Assoc. 2000:36:431-8.

7. Willis A, et al. Advances in topical glaucoma therapy. Vet Ophthalmol. 2002:5;9-17.

Feline Herpesvirus: Ocular Manifestations

By: Rachel Mathes, DVM, MS, Diplomate ACVO

Feline herpesvirus-1 (FHV-1) is a common viral agent in cats, ubiquitous in the feline population.1It is estimated that 90-95% of cats harbor the virus, usually as a latent infection.  Most often this virus does not cause clinical disease in healthy cats; however, a certain percentage of cats develop recurrent or recrudescent disease.1,2Neonatal infections may cause serious ocular disease or blindness.  Most often, however, if an adult cat is affected, this disease causes ocular morbidity with varied severity.3Viremia appears to be important in the initial infection, but may be of less importance in recrudescent disease.4FHV-1 is directly epitheliotoxic to conjunctival and corneal epithelial cells.  Because of this, the most common ocular manifestations of FHV-1 disease are keratitis and conjunctivitis.5Feline herpesvirus is difficult to detect using serology, PCR and VI (virus isolation), therefore, the diagnosis is usually made based on clinical suspicion of disease.4Feline herpesvirus 1 cause changes to the preocular tear film with affected cats having an increased tear film break up time (increased drying on the ocular surface) and decreased goblet cell density.6Clinical signs may vary with herpetic disease, but blepharospasm (squinting), blepharedema (eyelid swelling), conjunctival hyperemia, chemosis (conjunctival edema), variable corneal ulceration, and corneal vascularization are commonly present (figure).1Secondary signs related to chronic irritation may also be noted and include corneal sequestrae, entropion, dry eye disease, corneal perforation and secondary bacterial infections. Treatment is aimed at supportive care including tear stimulants, tear replacers, reducing environmental and external stressors, and topical antibiotics if corneal ulcers are present.  Antiviral therapy is sometimes recommended in severe cases of FHV-1 infections.7Options for antiviral medications include topical and/or systemic therapy.8Oral lysine has not been shown to improve the clinical signs of herpetic disease.9In fact, lysine has caused worsening of clinical signs in some studies.10This disease may be frustrating to treat and treatment may extend weeks, months or years.  Because the virus is so common in feline populations, caution is advised in treating any cat exhibiting signs of keratitis or conjunctivitis with a topical or oral steroid as steroids have been shown to cause viral recrudescence. 

          Image  ( A )

          Image  ( A )

                          Image ( B )

                        Image ( B )

 The left (A) and right (B) eye of a patient with clinical signs of herpesvirus are depicted.  Eyelid swelling, conjunctival hyperemia and chemosis are present in both eyes.  This patient was also sneezing on examination, a sign consistent with active herpetic disease. Both eyes were painful, as manifested by the third eyelid elevation.  The right eye has extensive corneal vascularization and corneal ulceration present.  Cats presenting with active corneal and conjunctival disease should receive supportive therapy +/- antiviral medications.  Topical and oral steroids should always be avoided.



1. Gould D. Feline herpesvirus-1: ocular manifestations, diagnosis and treatment options.  J Feline Med Surg. 2011; 13: 333-46.

2. Zicola A, et al. Feline herpesvirus 1 and feline calicivirus infections in a heterogenous cat population of a rescue shelter. J Feline Med Surg. 2009;11;1023-7. 

3. Wieliczko A, et al. Feline herpesvirus 1 and Chlamydophila felis prevalence in cats with chronic conjunctivitis. Pol J Vet Sci. 2010;13:381-3.

4. Westermeyer H, et al. Assessment of viremia associated with experimental primary feline herpes

5. Hillstrom A, et al. Evaluation of cytologic findings in feline conjunctivitis. Vet Clin Pathol. 2012;41:283-90.

6. Lim C, et al. Effects of feline herpesvirus 1 on tear film breakup time, Schirmer tear test results and conjunctival goblet cell density in experimentally infected cats.  Am J Vet Res. 2009;70:394-403.

7. Fontenelle J, et al. Effect of topical ophthalmic application of cidofovir on experimentally induced primary ocular feline herpesvirus-1 infection in cats. Am J Vet Res. 2008;69:189-93.

8. Thomasy S, et al. Pharmacokinetics of famciclovir and penciclovir in tears following oral administration of famciclovir to cats: a pilot study. 2012;15:299-306.

9. Rees T, et al. Oral supplementation with L-lysine did not prevent upper respiratory infection in a shelter population of cats. J Feline Med Surg. 2008;10:510-3.

10. Drazenovich T, et al. Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter. Am J Vet Res. 2009:70:1391-400.

Feline Heart Disease

Heart disease in domestic cats is actually quite common, which may come as a surprise to feline owners. It can strike any age or any breed of cat. One of the most challenging aspects of feline heart disease is that cats may not show any warning signs (such as exercise intolerance, coughing, weakness)until the process is very advanced. This means that a cat can literally be playing vigorously one day, and suddenly have trouble breathing. Untreated heart disease often progresses to heart failure, blood clot formation, and death.

The detection of a new heart murmur by your veterinarian (often on routine examination) can be the first sign that changes in the heart have taken place. While not every murmur signals the onset of heart disease, a further investigation is warranted since those murmurs which are a result of heart disease cannot be distinguished from "innocent" murmurs by routine tests alone.

Fortunately, advances in companion animal medicine enable veterinarians to efficiently diagnose cardiovascular disease in cats, even in its early stages. In many instances, if heart disease is detected prior to the stage of actual heart failure, it can be successfully controlled with medication(s). A feline with carefully controlled heart disease may live symptom-free for years!


The first test for heart disease begins with a thorough physical examination. During the exam, the veterinarian will determine your cat's heart rate and rhythm. A persistently elevated rate, or a rhythm that is irregular can be associated with heart disease in cats. The presence of a murmur (especially one not previously detected) may be further evidence of heart disease. In advanced cases of heart disease, abnormal sounds in the lungs may be heard. A weak or irregular pulse can also occur. The results of the physical exam may lead to further testing.

Chest Radiographs (x-rays)

Chest radiographs are important components in the diagnosis of feline heart disease. A diseased heart will most often enlarge over time. In advanced stages, fluid may be detectable in the chest cavity (pleural effusion) or in the lungs themselves (pulmonary edema).

Electrocardiogram (EKG or ECG)

An electrocardiogram (EKG or ECG) is a tracing of the electrical activity of the heart. It documents heart rate and rhythm. In addition, subtle changes can occur in the shape of the ECG spikes that can reveal certain types of pathological changes in the heart. It is a rapid and painless test that can be performed in the veterinary office.


An echocardiogram, also known as a cardiac ultrasound exam, is one of the most advanced and sensitive tests for determining the presence of heart disease in animals. It is painless and generally does not require sedation. The technique uses sound waves to actually visualize the heart in action. From this exam, the dimensions of each heart chamber can be determined.

Ultrasound can also detect the presence or absence of fluid in the sac around the heart (pericardial effusion), fluid in the chest, congenital heart defects, abnormalities of the heart valves, blood clots within the heart itself, or heart tumors (rare in cats). Most importantly, the echocardiogram can actually determine the type and degree of heart dysfunction. An accurate assessment of heart disease is paramount to effective treatment.


Dilative cardiomyopathy

Dilative cardiomyopathy denotes heart disease that results in an enlarged heart with thinning and weakening of its muscular walls. The weakened heart cannot pump efficiently which subsequently can lead to fluid accumulation in the lungs and/or chest cavity (analogous to congestive heart failure in humans). Enlargement of the heart can lead to leakage at the heart valves, creating a murmur.

This form, although more difficult to successfully control, has become less common in recent years. A few years ago, research showed that deficiency of the amino acid taurine in the feline diet was one of the main causes of dilative cardiomyopathy. Since that time, most commercially made feline diets are supplemented with taurine.

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is the most commonly diagnosed heart disease in cats. The walls of the heart become much thicker and stiffer than normal. This results in a smaller chamber to hold the blood, and diminishes the amount of blood pumped out with each beat. Consequently, the heart has to accelerate and use more energy to accomplish its original task. The geometric changes in the heart can lead to leakage at the valves, and development of a murmur. As the disease progresses, the heart can become so thickened that it cannot pump the blood forward at an adequate rate. This usually results in fluid accumulation in the lungs.

The cause in most cases is unknown, but genetics are thought to play a role in at least some cat breeds. While it is most common in middle-aged male cats, it can be seen in either sex as early as 6 months of age. Hypertrophic cardiomyopathy remains the most treatable form of feline heart disease.

Restrictive cardiomyopathy

Restrictive cardiomyopathy is a less common, less defined type of heart disease in cats. It is more difficult to detect, as many cats will have near normal echocardiograms, but their heart walls seems "stiffer" and less efficient at pumping blood forward. It is thought that in such cats the heart wall muscle cells become slowly replaced with less functional scar tissue. Cats with this type of disease may shows signs consistent with either dilative cardiomyopathy, hypertrophic cardiomyopathy, or both.


Therapy for feline heart disease depends on which type is diagnosed and how advanced the disease is. As previously mentioned, cats with hypertrophic cardiomyopathy have the best long term outlook The most serious consequences of progressive heart disease are weight loss, anorexia, difficulty breathing, weakness, and blood clot formation (with possible limb paralysis). Cats with advanced heart disease are at risk for sudden death.

Early detection and intervention, however, can be very rewarding for many cats and their owners.


Furosemide (Lasix‰) is a diuretic ("water pill") used in all types of feline heart disease. It reduces the volume of fluid that the heart has to pump, and removes fluid from the lungs. This makes the heart's work easier.


Enalapril (Vasotec¨ or Enacard‰) is a drug known as a vasodilator. It is very useful in many types of heart disease. It lowers blood pressure and reduces the workload of the heart. In dilating the vessels downstream from the heart, it lowers the resistance to blood being pumped forward.


Diltiazem (Cardizem‰) is a drug used in humans and animals. It is a "calcium channel blocker." Most commonly used for hypertrophic cardiomyopathy, it reduces the stiffness and work of heart walls. It has been documented to prevent or reverse wall thickening in many cats, and is very well tolerated.


Digitalis (Digoxin® or Lanoxin®) is a very old but useful drug utilized in people and animals mainly for treatment of dilative cardiomyopathy. It strengthens the contraction of the heart muscle with the goal of improving pumping function. It also can correct certain types of irregular heart rhythms. Because it has a narrow safety range, the drug concentrations in the patient's bloodstream must be monitored periodically.


Betablockers such as propranolol (Inderal®) or atenolol (Tenormin®) are prescribed mainly for hypertrophic cardiomyopathy. These drugs slow the rhythm of the heart, allowing the attenuated chambers to fully fill with blood between heartbeats. This increases cardiac output and thus reduces the actual work of the heart. Betablockers also lower blood pressure and regulate heart rhythms.


One of the health risks for feline heart disease patients is the formation f a blood clot in the heart. The clots can form in the enlarged heart chambers where the blood undergoes increased turbulence. If a piece of the clot leaves the left side of the heart and travels downstream, it often lodges in the large blood vessel known as the aorta. Since the aorta is the trunk artery carrying blood to the back half of the body, loss of this blood flow can cause temporary or permanent paralysis. The best prevention of this complication is to 1) adequately control the heart disease and reduce heart chamber size and 2) low dose aspirin therapy. While cats can have toxic or lethal reactions to high dose aspirin or any dose of acetaminophen (Tylenol®), low dose aspirin can often be used safely. The usual dose is 1/4 of an adult regular aspirin or 1 baby aspirin (81 mg.) per cat TWICE WEEKLY.

Vaccine Associated Sarcomas in Cats (VAS)

Dr. Gail Mason, DVM, MA, DACVIM
Kathi Smith, RVT, Internal Medicine & Oncology Technician

Vaccinating domestic cats against serious infectious disease is an important step in good quality health care. The diseases that are vaccinated for can cause serious illness and/or death. Vaccination against rabies is an important pet health, public health, and legal issue as well. However, due to statistical association between some vaccines and subsequent sarcoma development which was noted over the last decade, vaccine types and protocols are under heavy scrutiny.

Injection site sarcomas, as the name implies, can develop in areas of the body where vaccination has taken place. This typically is between the animal's shoulder blades (interscapular) or on a hind limb. These tumors are aggressive in nature and are associated with significant tissue inflammation and decay. They tend to infiltrate the normal tissues with malignant tendrils making surgical excision difficult. Although they are considered to be in the class of "soft tissue sarcomas," they have a higher metastatic rate than other tumors of this class.

Current recommendations suggest that masses noted at vaccine sites which are present 3 or more months post-vaccinations, are greater than 2cm or are rapidly growing should be dealt with in a timely fashion. An incisional biopsy can confirm a VAS. Matastasis can occur to local lymph nodes and to the lungs.

Staging of the patient to evaluate the extent of the disease may include: 
• Chest radiographs (x-rays) 
• Abdominal radiographs
• Routine blood screening
• Ultrasonography or a CT scan

Patients have longer survival times when an aggressive, initial resection is performed and is followed by radiation therapy. If the tumor is located on a limb, it may be necessary to perform a limb amputation. As unpleasant as this idea is, it is well-documented that patient recovery is rapid and quality of life can be excellent. Chemotherapy has also been used in the treatment of VAS but its exact efficiency remains to be determined. Most published veterinary medical reports have described use of either doxorubicin and/or carboplatin.

Unfortunately, cats with VAS may have a guarded to poor long term prognosis. Remission times are variable, but most often reported as being between 8 months to 1.6 years. Initial aggressive and complete resection appear to positively influence outcomes and longer, excellent quality remissions have been documented.

Soft Tissue Sarcomas

Soft Tissue Sarcomas (STS) in Cats and Dogs

Soft tissue sarcomas

Soft tissue sarcoma is a general term that refers to a group of tumors that form in tissues of mesenchymal origin such as the connective tissue (e.g. fat, smooth-muscle, blood vessels, lymph vessels, skeletal muscle, etc.) They tend to have similar histologic appearance and biological behavior, and can be either benign (noncancerous) or malignant (cancerous). Soft tissue sarcomas can arise in any part of the body although skin and subcutaneous (the layer of tissue directly underlying the skin) tumors are the most commonly observed.

Soft tissue sarcomas (STS) behave in a locally invasive manner. The incidence of metastasis (spread to different sites) varies from about 8% to 20%. This rate is generally lower than other types of tumors in animals; therefore, aggressive local control of the disease is the key goal.


The individual STS tumor types can be challenging to distinguish between. Fine-needle aspirates or tissue biopsies are required to confirm a diagnosis. Not infrequently, additional pathology tests are required to more precisely determine the tissue of origin. Also, additional tests are performed in order to evaluate how advanced the disease is. The tests will depend on the type of soft tissue sarcoma but generally involve blood and serum biochemical tests, chest X-rays and imaging.

Disease Staging

Imaging studies of the local tumor may be recommended prior to planning the surgical removal of the tumor and/or radiation therapy, especially in animals with suspected intra-abdominal soft-tissue sarcomas. Advanced imaging techniques such as CT (computed tomography) and MRI (magnetic resonance imaging) are especially useful due to their high level of resolution and detail.

Diagnostic tests that evaluate whether the tumors have spread to other organs include chest X-rays (to check for metastasis to the lungs), abdominal ultrasound (to check for metastasis in the spleen, liver, etc.) and fine-needle aspirates/biopsy of regional lymph nodes (to check for lymph node metastasis). At the very minimum, chest X-rays should be performed prior to initiating treatment since soft tissue sarcomas commonly spread to the lungs. Lymph node metastasis is not common for typical soft tissue sarcoma but their biopsy/cytology should be assessed in animals whose lymph nodes appear abnormal and/or whose specific tumor type is suspected to have a high metastatic potential.

Treatment Options


Invasive STS can be challenging to treat as they expend into surrounding structures and require extensive surgery to achieve complete removal. The first surgery is the key opportunity to achieve complete excision. A general principle for removing such tumors is that the tumor should be removed with a significant margin of normal tissue around it (in all directions) to ensure complete removal of all malignant cells. An experienced, board-certified veterinary surgeon is recommended for STS resections.

Some STS appear in locations in which complete resection is difficult without disturbing normal tissue. Depending upon the tumor location, such surgeries as limb amputation, rib resection, and nasal/jaw reconstructions may be required. It is important to note that veterinary patients recover quickly and cosmetically even from these more extensive surgeries.

Radiation Therapy

Radiation therapy can be combined with surgery in either a pre or post-surgical manner. If given prior to surgery, the tumor may decrease in size and be subsequently easier to remove. If radiation therapy is given after surgery, it is intended to eradicate tumor cells which may have left behind during an incomplete excision.

Veterinary patients are quite tolerant of this form of cancer treatment and it can increase the changes for successful long term disease management. This is a highly specialized form of cancer treatment and is provided by veterinary radiation oncologists at:

  • New England Veterinary Oncology Group (NEVOG), Waltham, MA. 781-684-8688

  • Angell Memorial Animal Hospital, Boston, MA. 781-522-7282

  • Tufts University School of Veterinary Medicine, N. Grafton, MA. 508-839-5395


The benefit of chemotherapy in the treatment of soft tissue sarcomas has not been quantified. However, recent research has shown that chemotherapy can delay regrowth or spread of aggressive soft tissue sarcomas. Chemotherapeutic agents used include doxorubicin, carboplatin, and certain alkylating agents. Low-dose daily metronomic chemotherapy is also showing promise as treatment for STS. In general, chemotherapy is recommended in patients deemed to have an aggressive tumor (high grade), metastatic disease, and/or intra-abdominal tumors.


The prognosis for soft tissue sarcoma is variable, though long term control or cure is possible. Local control of the tumor is very challenging and local tumor recurrence rates after surgery (with or without radiation) range from 7% to 32%. Poor prognostic factors for local tumor recurrence include large tumor size, incomplete surgical removal and high histologic tumor grade (high grade corresponds with aggressive tumor behavior). Management of recurrent soft tissue sarcomas is usually more difficult than the original tumor, emphasizing the need for aggressive treatment of the initial tumor. Because the median time for tumor recurrence is 368 days, the pets should undergo long term follow-up and frequent check-ups. The metastatic rate for soft tissue sarcomas varies from 8% to 17% with a median time to metastasis of 1 year, depending on the tumor’s properties. The median survival time for dogs with soft tissue sarcomas is 1416 days with surgical treatment and 2270 days with surgical and radiation treatment. Overall, up to 33% of dogs eventually die of tumor related causes.

Types of Soft Tissue Sarcomas

Tissue of origin

Benign tumor

Malignant tumor

Primary sties

Risk of malignant tumor metastasis

Organ of metastasis

Adipose (fat) tissue



Limbs, abdominal or chest cavity

Low to moderate

Lungs, liver, spleen, bone

Fibrous tissue



Limbs, oral cavity

Low to moderate


Histiocytic cells


Histiocytic sarcoma


Moderate to high

Lymph nodes, lungs, spleen, liver, kidneys

Lymph vessels





Lymph nodes

Blood vessels



Spleen, heart, liver, muscle, bone, kidneys


Lungs, liver, lymph nodes, distant dermal sites

Nervous tissue


Peripheral nerve sheath tumor


Low to moderate


Skeletal muscle



Tongue, larynx, heart, bladder

Low to moderate

Lungs, liver, spleen, kidneys

Synovial tissue


Synovial cell sarcoma


Moderate to high

Lymph nodes, lungs

Myxoma tissue



Limbs, joints

Low to moderate


Source: Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology, St. Louis: Saunders Elsevier, 2007.

Anal Sac Tumors in Cats and Dogs

Anal Sac (Apocrine Gland) Tumors in Dogs and Cats

*    Anal sac (apocrine gland) tumors can be found by rectal examination.
*    Common symptoms include difficult or painful bowel movements, scooting, swelling around the anus, ribbon-like stool and bleeding as a result of local irritation.
*    Anal sac tumors can result in high calcium levels, which will cause increased thirst increased urination, decreased appetite, weight loss, vomiting, muscle weakness, and low heart rate.                                        
*    Surgical removal of anal sac tumors is the treatment of choice whenever possible.
*    It is estimated that the cancer has spread in 50-80% of cases at the time of diagnosis.
*    Dogs whose cancer spread to other organs have a median survival of 6 months after surgery compared to 15.5 months for dogs without metastases (spread of the cancer).
*    The tumors typicall occur in older dogs and some studies suggest that females may be at higher risk of anal sac cancer.  

Anal sac tumors
     Anal sacs are paired structures, one sac on each side of the anus, which are lined by many glands. These glands produce liquid that is expelled with each bowel movement as a form of territorial marking. Anal sac tumors arise from the glands of the anal sac, and may be either benign (known as anal sac adenomas) or malignant (known as anal sac adenocarcinomas). Anal sac adenocarcinoma is very rare in cats, but has been reported. The tumor itself usually affects only one of the two anal sacs; however, some pets may have tumors in both. The tumor can be very small or quite large, sometimes producing a hormone which causes blood calcium levels to rise above normal levels. The high level of calcium is called hypercalcemia, and can cause problems by damaging the kidneys. Unfortunately, by the time the diagnosis of anal sac adenocarcinoma is made, the tumor may have already metastasized (spread) to other sites such regional lymph nodes, lumbar spine or the liver, spleen, or lungs.

     Anal sac adenocarcinomas are usually identified during physical examination of the anus, although some tumors are not always easily felt. Some tumors are found during routine rectal examination for impacted anal glands or when taking the animal's rectal temperature. If a mass is detected veterinarians will typically perform several follow-up tests. Complete blood count (CBC), serum chemistry profile, and urinalysis will identify possible hypercalcemia, evaluate the pet’s overall health, and help identify any other abnormalities. To confirm whether the mass is benign or malignant, a fine needle aspirate or tissue biopsy is performed. Incisional biopsy (when a small piece of the tumor is taken) is usually performed on large tumors under sedation and local anesthesia whereas excisional biopsy (when the entire tumor is removed) is usually performed on small tumors under general anesthesia. Additionally, cells can also be isolated from the sublumbar lymph nodes (lymph nodes that are close to the anal sac and the first site to which the tumor will spread) to determine if the tumor has already spread to this region. To test whether the cancer has spread to other organs, abdominal X-rays, chest X-rays and abdominal ultrasound are performed. Advanced imaging techniques such as CT scans can be used to get a more precise and more complete assessment. 

Treatment options
    The initial treatment for anal sac tumors is complete surgical excision. Whenever possible, the surgery will remove the anal sac tumor as well as a wide margin of normal tissue around and under it in order to maximize the likelihood that no tumor cells are left behind. Depending on the tumor’s size, its surgical removal may very infrequently result in fecal incontinence and you should discuss this with your veterinary surgeon to get a clearer idea of its severity given your pet’s condition. If recovering well without complications, most pets are discharged 1-2 days after surgery. Pets may need to take stool softeners until tissue swelling is resolved, and pain medications should be prescribed to make the pet more comfortable given the invasive nature of surgery.

     Metastasis (spread of the cancer) to the nearby sublumbar lymph nodes occurs in more than 50% of cases, therefore, their surgical removal may be required if the lymph nodes are enlarged. If the pets showed increased levels of calcium (hypercalcemia), it will usually resolve on its own 24-96 hours after the surgery, however, it is recommended to periodically measure the pet’s calcium levels to monitor possible cancer recurrence or metastasis. Pets with persistently high calcium levels may be given medication in order to prevent damage to the kidneys. 

     In addition to surgery, chemotherapy may be used to kill any remaining cancer cells left behind after the surgery. Even if there is no evidence of metastasis at the time of diagnosis, it is possible that some tumor cells are already circulating throughout the pet’s body, getting ready to establish new tumors in distant organs. Chemotherapy can also be used in pets if the tumor could not be removed with surgery, has already metastasized at the time of diagnosis, or if the surgery was not able to remove all of the tumor. While unlikely to cure the cancer, it can offer the pet more quality time.  Many patients experience successful management of their disease for months to up to two years.  

Radiation therapy
     Radiation therapy is typically used to treat anal sac tumors that could not be removed by surgery or if the surgery was not able to remove the entire tumor.

Treatment associated risks
     Any surgical procedure has the rare risk of anesthetic death but use of modern anesthetic protocols and careful monitoring have largely minimized the risk. Because the surgery is performed near the anus, there is an increased likelihood of developing an infection but the administration of antibiotics after the procedure should control this potential complication. If the sublumbar lymph nodes are also being removed, there is a risk of bleeding during the surgery because the tumor-invaded lymph nodes are often closely associated with blood vessels. These lymph nodes are also very close to nerves, especially those connecting with the bladder, and their removal may cause nerve damage leading to temporary or in some cases permanent post-operative urinary incontinence (inability to control urination). Fecal incontinence (inability to control bowel movement) can occur in a small percentage of animals after the surgery. For pets having difficulty defecating, high-fiber diet and/or stool softeners are usually prescribed to alleviate this problem. Pets undergoing radiation treatment may experience radiation complications such as mild to severe moist desquamation (shedding of skin cells that were exposed to radiation), colitis, difficulty to empty the bowel, and discomfort.

     The prognosis will largely depend on the extent of the disease at the time of diagnosis. Pets with local disease (has not spread to other organs) whose tumor was completely removed by surgery have a much better prognosis than pets whose cancer has already spread, or whose tumor could not be completely removed. 

     There is only limited number of published studies regarding outcomes of anal sac tumors in pets. One study of 32 dogs showed that female dogs had a worse prognosis compared to male dogs, and had a 50% chance of cancer recurrence (cancer coming back) after surgery. It is estimated that by the time diagnosis of anal sac tumors is made, the cancer has spread in 50-80% cases. Dogs whose cancer metastasized had a median survival after surgery of 6 months (range from 1.5 to 39 months) whereas dogs without metastasis had median survival after surgery of 15.5 months (range from 3to 35 months).

     The largest published study involved 113 dogs with varying stages of anal sac cancer treated with different therapies. Of these 113 dogs, 104 underwent treatment consisting of surgery, radiation therapy, chemotherapy or combination. The results showed that median survival for the treated dogs was 544 days (meaning that at 544 days, 50% of the dogs were alive). The study also showed that dogs treated with chemotherapy alone had shorter survival (median of 212 days) compared to those who received other treatments (median of 584 days). Dogs who did NOT receive surgery experienced shorter survival (median of 402 days) compared to those who did undergo surgery (median of 548 days). For dogs with large tumors (>10cm2), the median survival was 292 days compared to 584 days for those with smaller tumors (<10cm2). Dogs whose blood tests show increased calcium levels faced shorter survival (median of 256 days) compared to those with normal calcium levels (median of 584 days). Dogs with metastases to the lungs had significantly shorter median survival (219 days) compared to those without metastases (548 days) (Williams, J Am Vet Med Assoc, 2003)