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TANYA'S
FELINE CHRONIC RENAL FAILURE INFORMATION CENTRE
RELATED DISEASES
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There are several other diseases which can occur in CRF cats. It is important to know about these diseases so that they can also be treated if they are present; doing this gives you a better chance of managing all of them, although sometimes it can feel like a real juggling act. These diseases are divided into two types, diseases which may accompany CRF and diseases which may trigger CRF. This section contains the following:
1. Diseases Which May Accompany CRF
Hypertrophic Cardiomyopathy (Heart Disease)
There are various kinds of heart disease but hypertrophic cardiomyopathy (HCM) is the most common one in CRF cats. Cardiomyopathy means disease of the heart muscle, and in HCM the left ventricle of the heart, which pumps blood through the aorta, the body's largest artery, is thickened. This thickening stops the heart expanding properly.
HCM may be caused by hyperactive thyroid - in fact, Gulf Coast Veterinary Specialists claim that 87% of hyperthyroid cats will have some degree of HCM. Other possible causes include high blood pressure or CRF, and in some cats, such as Maine Coons or Ragdolls, HCM is a genetic problem - The Winn Feline Foundation explains more about this. However, it is also possible for a cat to have HCM without any associated disease.
Some cats with HCM may have a heart murmur, although it is also possible to have a heart murmur without having HCM. Heart murmurs are caused by blood flowing through the heart turbulently rather than smoothly. They are graded from 1 to 6 depending upon their severity, with 1 being the lowest level at which a murmur can be heard and 6 being the most severe, extremely loud murmur, which is often audible without a stethoscope.
Heart murmurs may or may not need treatment, depending upon their cause and their severity. Both anaemia and hyperactive thyroid may cause a heart murmur which disappears following suitable treatment.
Merck Veterinary Manual has detailed information on heart murmurs. University of California at Los Angeles - on this site you can listen to the different types of heart murmur - turn your speakers up loud for best effect. This is a human site but it should still give you an idea of what to listen for. Heart Sounds - you can listen to various heart sounds here.
Congestive Heart Failure (CHF) As heart disease and/or renal disease progress, the cat may enter congestive heart failure. Anaemia increases the risk of CHF developing, so should always be treated if present. In CHF, the heart is really struggling to cope and fluid may accumulate in the lungs (pulmonary oedema), or around the lungs (pleural effusion) or in the abdomen (ascites). Many cats with CHF only have a short period to live, although it is usually worth trying to control the condition because, as with CRF, some cats do better than others. Treatment commonly includes the use of diuretics.
If your cat develops CHF within a week of starting corticosteroids, this might possibly be the cause. One study, Corticosteroid-associated congestive heart failure in 12 cats (2004) Smith SA, Tobias AH, Fine DM, Jacob KA, Ployngam T The International Journal of Applied Research in Veterinary Medicine 2 (3) pp159-170 found that some cats developed a unique form of congestive heart failure (CHF) within seven days of starting steroids. Five of the cats died, but the seven that survived did much better than the typical CHF patient once taken off the steroids.
Cancer Back Up explains more about pleural effusion. Health A to Z explains more about ascites. Vetgo discusses the usual treatments for congestive heart failure. Warning signs for congestive heart failure is a helpful site by an individual whose cat, Coco, had both CRF and heart problems, and gives useful information on what to watch for. Coco lived with CHF for quite some time. Emergency respiratory assessment (2001) Hughes D is a presentation to the World Small Animal Veterinary Association World Congress 2001. It is rather technical but may still be of use. Mar Vista Vet has information on long term therapy for heart failure. Effect of coenzyme Q10 therapy in patients with congestive heart failure: a long-term multicenter randomised study (1993) Morisco C, Trimarco B, Condorelli M Clinical Investigation 71 (8 Supp) pp134-6 demonstrated "that the addition of coenzyme Q10 to conventional therapy significantly reduces hospitalization for worsening of heart failure and the incidence of serious complications in patients with chronic congestive heart failure".
Unfortunately many cats are asymptomatic or show very few symptoms, which can make heart disease hard to diagnose and treat. One of our cats, Harpsie, was suspected of having heart disease because of a high heart rate on two vet visits (which might just as easily have been caused by stress or "white coat syndrome") and weight loss. Other possible symptoms can be similar to those of CRF, including lack of appetite, lethargy and vomiting. You may also see faster breathing (the normal respiratory rate of a cat is around 20-30 respirations a minute).
Fluid Build-Up/Congestive Heart Failure More serious symptoms, which require urgent veterinary help, include sudden weight gain, difficulty breathing, coughing or open mouth breathing. These may be a symptom of fluid build-up, which may be a sign of congestive heart failure or, rarely, of nephrotic syndrome. A low body temperature may also be seen in congestive heart failure.
In CHF, fluid collects in the lungs (pulmonary oedema), or around the lungs (pleural effusion) or in the abdomen (ascites). Cancer Back Up explains more about pleural effusion.
If left untreated, fluid build-up can kill, so the fluid should be removed. Diuretics in pill form are commonly used to remove excess fluid, but these take a few days to take full effect. For immediate relief, thoracocentesis (needle aspiration) may be performed: this entails inserting a fine needle into the chest and drawing the fluid off. It sounds horrible, but my cat had this done to remove ascites and he didn't even flinch. However, it is a delicate procedure, and skill is required to insert the needle in the right place and remove the correct amount of fluid. But it can be lifesaving.
Saddle Thrombus (Blood Clot in the Legs) Other symptoms may include limping or an inability to use the legs, particularly the hind legs. Affected legs are likely to be cold to the touch. This symptom can be caused by a blood clot in the aorta which stops the blood supply to the legs (sometimes known as a saddle thrombus). This is life-threatening so you should consult a vet as soon as possible. If your vet proposes a treatment plan, make sure it includes painkillers because this is an extremely painful condition.
University of California at Davis has some information on blood clots in cats. Manhattan Cats also has some detailed information on blood clots, including possible treatment options. Systemic arterial embolism in cats (2007) is a presentation by Dr C Atkins to the World Small Animal Veterinary Association World Congress 2007 which discusses treatment and prevention. Feline thromboembolism - new clinical perspectives (2007) is a presentation by Dr PR Fox to the World Small Animal Veterinary Association World Congress 2007 which discusses treatment options. Oakland Veterinary Referral Services has a good overview of treatment options for saddle thrombus.
Weak legs (as opposed to limping) may also have other causes, see Index of Symptoms and Treatments.
How cats cope with heart disease varies from cat to cat, depending upon how advanced the disease is and how well the cat responds to treatment. Try to keep stress to a minimum.
The only way to obtain a definitive diagnosis of HCM is by way of echocardiogram (ECG or ultrasound), ideally with Doppler colour flow imaging. Your vet may also wish to run x-rays in order to obtain further information, but x-rays alone will not normally provide a proper diagnosis. However, x-rays can be helpful if your vet suspects some kind of lung involvement, and are the only way to diagnose pleural effusion, pulmonary oedema or ascites (see congestive heart failure). If at all possible, ask for a referral to a veterinary cardiologist.
The Feline Advisory Bureau in conjunction with the Veterinary Cardiovascular Society has set up an HCM screening scheme for UK cats. Feline cardiomyopathy - establishing a diagnosis (2002) Fuentes VL, is a presentation to the 26th Annual Waltham/Ohio State University Symposium. Laboratory tests for the diagnosis of heart disease and failure in dogs and cats (2007) is a presentation by A Boswood to the World Small Animal Veterinary Association World Congress 2007 which discusses the use of "cardiac" laboratory tests.
If your cat's HCM is caused by a hyperactive thyroid (hyperT), treating the hyperT successfully can reverse much or even all of the HCM; while a heart murmur caused by anaemia may also be improved following treatment. Otherwise, HCM cannot be cured but it can be controlled by way of drugs. Unfortunately many drugs which help the heart condition put strain on the kidneys, so if your cat has both heart disease and CRF, discuss which drug to use with your vet. It must be emphasised that it is essential to treat heart disease if it is present, and that treating the heart disease must take precedence over treating the CRF, which is an academic problem if the heart stops beating.
Even if your cat appears stable once medication has begun, it is a good idea to have an ultrasound examination of your cat's heart undertaken once every year (or more regularly if your cardiologist advises it) and to review medication at that time if appropriate.
Cats with congestive heart failure may need to have fluid build-up removed from their lungs manually (thoracentesis) or via diuretics, in addition to other treatments. If your cat has CHF, it is worth asking your vet to teach you to listen to your cat's heart so you can monitor for any changes that might indicate an approaching crisis.
Washington State University College of Veterinary Medicine has some suggestions on how to care for a heart patient at home. Mar Vista Vet has information on long term therapy for heart failure.
Commonly Used Heart Medications HCM is usually treated with drugs and it is fairly common to use more than one heart medication at a time.
Feline cardiomyopathies (2001) is a paper presented by Paul Pion to the World Small Animal Veterinary Association World Congress in 2001, which gives typical heart drug dosages. The Mayo Clinic has a table showing the mechanism of some of the different classes of heart medications and their possible side effects.
The different drug classes are:
Beta Blockers Drugs called beta blockers are used to slow a fast heart rate. This is often the treatment of choice in the USA, where a drug called Atenolol is used. In the UK, a similar drug called Propranolol may be used.
Pharmacokinetics of atenolol in clinically normal cats (1996) Quinones M, Dyer DC, Ware WA & Mehvar R American Journal of Veterinary Research 57(7) pp1050-3 discusses the effects of atenolol on cats.
ACE (Angiotensin-Converting-Enzyme) Inhibitors These are drugs which prevent the conversion of a hormone called angiotensin I into another hormone called angiotensin II, the role of which is to constrict blood vessels. Therefore by using these drugs the blood vessels relax and this makes it easier for the heart to pump blood through the body. You should be careful if you are using ACE inhibitors at the same time as potassium supplements, because they may cause potassium levels to become dangerously high.
ACE inhibitors are a popular treatment for heart disease in the UK, and a commonly used one is Enalapril, the trade name of which is Enacard, which is also available in the USA. Mar Vista Vet has information and cautions on the use of Enalapril, including when using it in conjunction with diuretics such as frusemide (US: furosemide) (see below).
Another ACE inhibitor, Fortekor (benazepril), is licensed for the treatment of CRF in cats in the UK, Europe and Australia, even for cats without heart disease, and further information on this can be found on the Treatments page. Some US vets occasionally use enalapril in CRF cats for the same reason.
An ACE inhibitor called Ramipril (marketed as Altace or Vasotop) is available in the UK and Europe, though I only know of a couple of people who have used it for their cat. The efficacy, tolerance and safety of the angiotensin converting enzyme inhibitor ramipril in cats with cardiomyopathy with or without hypertension (2002) Schille F & Skrodski M is a paper presented to the World Small Animal Veterinary Association World Congress 2002.
It is not unusual for cats suffering from congestive heart failure to be given both an ACE inhibitor and a diuretic.
Calcium Channel Blockers Calcium channel blockers work by slowing the passage of calcium into muscle cells; this makes muscle in the blood vessels relax, so the blood vessels open wider. The most commonly available one in the UK is called Diltiazem which is also available in US.
Broncho-Dilators These are used in asthma, but can also be used to treat heart problems - they open up constricted airways in the lungs. Millophyline-V (etamiphylline) is commonly used on the UK; theophylline is commonly used in the US and may also be offered in the UK.
Veterinary Partner has information on the use of theophylline.
Diuretics may be used for congestive heart failure in order to rid the body of excess fluid. They are also used occasionally when a cat in the end stages of CRF has stopped urinating (anuria), in an attempt to "kickstart" the kidneys. The most common diuretic used in the UK is a drug called frusemide (furosemide in USA), which is commonly sold under the name of Lasix, although the name is currently being changed to Salix. Lasix is very hard on the kidneys, but some people have found that another diuretic, spironolactone, is gentler. However, Lasix is the best choice during times of crisis.
It is not unusual for cats suffering from congestive heart failure to be given both an ACE inhibitor and a diuretic.
Lactulose may exacerbate the effects of diuretics. Drugs.com has more information about this.
Washington State University College of Veterinary Medicine has information on the different types of diuretics. Mar Vista Vet has more information on Lasix (frusemide or furosemide), including cautions about using diuretics at the same time as ACE inhibitors. Pet Place has more information about spironolactone.
Aspirin Aspirin may be used in an attempt to reduce the chances of blood clots forming. Aspirin can be toxic to cats, who can only metabolise it very slowly, and should only be given to a cat on veterinary advice; it is usually only given in very low doses once every three days. In the USA, cats with HCM are routinely given carefully assessed doses of aspirin in addition to other medications, but if the cat reacts badly, then aspirin is stopped.
Mar Vista Vet has information on aspirin.
Veterinary Heart Disease Sites Long Beach Animal Hospital - explains how the heart works, and the Specific Diseases link discusses HCM. Vetinfo an overview of feline heart problems and medication by a US vet. Vetinfo CRF - this is a reply by the same vet to a query about the use of the usual heart medications in cats with CRF, particularly ACE inhibitors such as enalapril (Enacard) or benazepril (Fortekor). Cardiorespiratory diseases of the dog and cat is the online version of a detailed book by a veterinary cardiologist.
Feline Advisory Bureau - an overview of HCM by the UK feline charity. Boo Boo's Story - this is a site about Boo Boo, a cat who was treated for both CRF and HCM using holistic methods. Ragdolls - Ragdolls (and Maine Coons) can be prone to HCM, and this site has good pictures of a healthy heart and an HCM-affected heart. Jody Chinitz's Site - this site is by a lady who lost a cat to HCM.
Heart Support Sites Feline Heart List - a support list for people with cats with heart conditions, where you can obtain feedback on treatments, and support on living with HCM and other feline heart problems. The thyroid gland is situated at the front of the neck, and is responsible for the regulation of metabolism. When the thyroid is overactive, it speeds up metabolism, and as a result all the body's processes speed up. Hyperactive thyroid (hyperT) is very common in older cats.
Some of the symptoms of hyperT are similar to those seen in CRF, including weight loss, increased urination, increased thirst, a greasy coat, spiky fur and sometimes vomiting or hoarseness. HyperT cats may also scratch a lot and pull out their fur (Newman Veterinary has a photo of the result of such behaviour). There are other symptoms that may be seen such as increased appetite, restlessness, howling (especially at night), an increased heart rate (tachycardia) and sometimes a heart murmur. Hypertension is also fairly common in cats with hyperT. However, just to confuse matters, some hyperT cats have "apathetic hyperthyroidism", and become lethargic and lose their appetite instead.
HyperT was unknown in cats until the late 1970s, so there is much speculation about the possible causes. This section contains information on current research into possible (but as yet unproven) causes.
Epidemiologic study of relationships between consumption of commercial canned food and risk of hyperthyroidism in cats (2004) Edinboro CH, Scott-Moncrieff JC, Janovitz E, Thacker HL & Glickman LT Journal of the American Veterinary Medical Association 224 (6) pp 879-886 was a study during which the records of just under 170,000 cats over a 20 year period were examined. The study indicates that the consumption of canned food appears to carry an increased risk (almost four times the risk compared to cats who ate dry food) of developing hyperthyroidism, and that the risk increases for every year that the cat eats canned food. The reason for these findings is not known at this time, but it may possibly be related to the lining used in these tins, bisphenol-A (BPA), a potential endocrine disrupter. Males appeared to be at risk only if they ate pop-top cans, i.e. standard tinned food did not appear to carry a risk. However, females appeared to be at increased risk whether they ate pop-top cans or non-pop-top cans.
Whilst this is a worrying study, generally speaking cats do better on a wet food diet (see Food Composition and Nutritional Requirements). A possible solution might therefore be to feed food in foil pouches or plastic trays. If you do use tins, be sure to store any leftover food in glass containers in the fridge rather than in the tins themselves. The Food Standards Agency has more information on this.
University of Purdue, which led the study, provides a summary of the study findings. Evaluation of dietary and environmental risk factors for hyperthyroidism in cats (2000) Martin KM, Rossing MA, Ryland LM, DiGiacomo RF, Freitag WA Journal of the American Veterinary Medical Association 217(6) pp853-856, found that "cats that preferred fish or liver and giblets flavors of canned cat food had an increased risk". Effect of dietary soy on serum thyroid hormone concentrations in healthy adult cats (2004) White HL, Freeman LM, Mahony O, Grahan PA, Hao Q & Court MH American Journal of Veterinary Research 65(5) pp586-91 found that soy in a healthy cat's diet may increase T4 levels.
Elevated PBDE levels in pet cats: sentinels for
humans? (2007) Dye JA, Venier M, Zhu L, Ward CR, Hites RA &
Birnbaum LS Environmental Scientific Technology
The feline thyroid gland: a model for endocrine disruption by PBDEs? (2007) Mensching DA, Ferguson D, Bordson G, Scott J, Piwoni M, Beasley V is a summary of the goals of a two year study (completed in June 2007) which is also investigating the significance of PBDEs in cat food and the possible link between PBDEs and the development of hyperT in cats. Scroll down to pages S-102-3.
The vet can often feel a nodule in the thyroid. Blood tests are also used for definite diagnosis - these measure a hormone produced by the thyroid gland, thyroxine (T4). However, as the Winn Feline Foundation mentions, a small number of cats with hyperthyroidism may have normal T4 levels because levels may fluctuate throughout the day, and you may just happen to test when the level looks normal. Therefore many vets also routinely check levels of another hormone, tri-iodothyronine (T3). In a hyperT cat, levels of both hormones are usually elevated, although sometimes only one of them is higher than normal. The vet may also detect high blood pressure and/or a higher heart rate than usual, while the heart may be enlarged.
Please note that, as Mar Vista Vet mentions, the normal ranges do not apply to older cats (over the age of 10): be sure your vet allows for this when interpreting test results.
Occasionally the above tests may appear normal, but if you still suspect your cat has hyperT, you should ask your vet for a free T4 by equilibrium dialysis test; this test should not be relied upon in isolation (have it run it in conjunction with T4 and T3 tests), but can assist with making a diagnosis. Links with information on this issue include: Michigan State University has a very helpful overview of the significance of the various tests. Newman Veterinary also has some information on the use of the free T4 by equilibrium test (click on hyperthyroid diagnosis, an update). Mar Vista Vet also has more information about borderline T4 levels. Feline hyperthyroidism: those difficult diagnoses (2006) Schori JL Clinician's Brief Journal June 2006 discusses the problems of obtaining an accurate diagnosis.
Occasionally a cat may have low levels of the thyroid hormones and appear to be hypothyroid. True hypothyroidism is extremely rare in cats, and in the case of a CRF cat, this is more likely to indicate that the cat has "euthyroid sick syndrome". This occurs when the T4 levels appear lower than they actually are because of another concomitant disease such as CRF. Once the accompanying disease is under control, the thyroid hormones should return to a normal level. Newman Veterinary discusses euthyroid sick syndrome. Emedicine also discusses euthyroid sick syndrome.
It is essential to treat hyperT because hyperT is a strain on the cat's body, particularly the heart. However, you do need to proceed cautiously. If a cat has both CRF and hyperT, the hyperT can actually mask the effects of CRF; but once the hyperT is treated the CRF can then appear to worsen. In some cases, previously undiagnosed CRF may actually appear for the first time once hyperT is treated. Feline hyperthyroidism and its relation with renal function (2006) Daminet S Presentation to the 31st World Small Animal Veterinary Association World Congress has a table summarising the results of treating hyperT in a number of different studies in cats using the usual treatments.
There are three forms of treatment, all with advantages and disadvantages:
Drugs: Methimazole and Carbimazole A drug called methimazole, which regulates production of thyroid hormone, is the most common treatment in the USA, and was recently introduced in the UK. Trade names for methimazole are Tapazole (USA) and Felimazole (UK).
Methimazole is a relatively simple way of treating hyperT but it can have side effects such as lack of appetite, vomiting and even anaemia in some cats; plus it only controls the condition, it will not cure it. Veterinary Partner discusses possible side effects, including itching, particularly on the face. Cats on methimazole may also have elevated liver enzymes and low white blood cells.
If your vet recommends this treatment method, try to start at the lowest dose possible and increase if necessary, because this reduces the risks of an adverse reaction: in Diagnostic and treatment options for feline hyperthyroidism (2003), a presentation to the World Small Animal Veterinary Association World Congress, Richard Nelson recommends starting at a dose of 2.5mg once a day for the first two weeks, increasing to 2.5mg twice a day if the cat is showing no adverse reaction and tests indicate that a higher dose is required (these doses are per cat, not per pound or kg).
Carbimazole used to be the drug treatment of choice for hyperT cats in the UK, but once methimazole in the form of Felimazole was introduced, vets became legally obliged to provide methimazole first.
If your cat nevertheless does badly on methimazole, you may wish to try carbimazole instead and see if your cat does better on that. Carbimazole is actually converted to methimazole in the cat's body, but nevertheless it tends to have fewer side effects, probably because carbimazole appears to act more slowly than methimazole and is absorbed less quickly. Several cats on the Feline CRF lists have done better on carbimazole than on methimazole.
Carbimazole can be obtained in the USA from compounding pharmacies (see Tips on Medicating Your Cat; Island Pharmacy for one will compound carbimazole). It is available from vets in the UK in pill form for cats who do not do well on methimazole. Similarly to methimazole, a cautious starting dose is recommended of 2.5mg once a day for the first two weeks, increasing to 2.5mg twice a day if the cat is showing no adverse reaction and tests indicate that a higher dose is required (these doses are per cat, not per pound or kg). However, unlike methimazole, carbimazole may be given up to three times a day if necessary.
Newman Veterinary mentions that there are fewer side effects with carbimazole than with methimazole. Plumb's Veterinary Drug Handbook also mentions this. Feline hyperthyroidism: spectrum of clinical presentations and response to carbimazole therapy (2000) Bucknell DG Australian Veterinary Journal 78 (7) mentions that there is less chance of side effects with carbimazole than with methimazole.
The second treatment method for hyperT is surgical removal of the thyroid gland, which is known as thyroidectomy. Although this is usually successful, it is of course invasive and too much of the gland may be removed, resulting in the opposite problem, an underactive thyroid (hypoactive thyroid). This treatment may be risky for cats with undiagnosed CRF (see below).
Radioactive Iodine Treatment (I131) The third possible treatment for hyperT is radioactive iodine treatment (I-131). This destroys the overactive thyroid tissue and has no major side effects, but it may be hard to obtain because it is only available in a limited number of places, and the cat has to be hospitalised for a period ranging from a few days to as long as six weeks in a few cases.
However, this treatment is usually considered unsuitable for cats who already have CRF, and may be risky for cats with undiagnosed CRF. This is because, if a cat has both CRF and hyperT, the hyperT can actually mask the effects of CRF; but once the hyperT is treated the CRF can then appear to worsen. In some cases, previously undiagnosed CRF may appear for the first time. This is not a small risk: according to Hyperthyroidism and the kidney (2006) Langston CE & Reine NJ Clinical Techniques in Small Animal Practice 21(1) pp17-21, "overt renal failure occurs in approximately 30% of cats treated for hyperthyroidism". If you are using drug treatment, you can adjust the dose to compensate for this, but this is not possible with the surgical and radioactive iodine treatments.
If you are considering this method of treatment and are in the USA, you may wish to consider using the iohexol clearance test, which measures your cat's GFR (see Methods of Early Detection), so you can tell beforehand if your cat is at risk of CRF following treatment.
Washington State University recommends treating with medication in the first instance. Effects of methimazole on renal function in cats with hyperthyroidism (2000) Becker TJ, Graves TK, Kruger JM, Braselton WE and Nachreiner RF Journal of the American Animal Hospital Association 36 pp215-233 is a study on the use of methimazole in cats and its effects on unmasking CRF. Long term health and predictors of survival for hyperthyroid cats treated with iodine 131 (2001) Slater MR, Geller S, Rogers K Journal of Veterinary Internal Medicine 15 pp47-51 is a study of the survival rate of 231 cats treated with the I-131 treatment which found that having renal disease adversely affected the chances of survival following this type of treatment.
If a cat has heart problems, however, treating the hyperT can often reverse the heart problems.
Mar Vista Vet - a US site with useful information on symptoms and treatments. Winn Feline Foundation has an overview of hyperT. Gulf Coast Veterinary Specialists has an interesting overview of hyperT. Pet Education has a helpful article about hyperT. Vetinfo - an overview of hyperT by a US vet. Feline Advisory Bureau - an overview of hyperT in cats by the UK feline charity. Feline hyperthyroidism: not just a skinny old cat is an article by Dr Katherine Dodds about juggling CRF and hyperT. Advanced Veterinary Medical Imaging - more information on the treatments available for feline hyperT. Feline HyperT list is a support list for people with hyperT cats, where you can obtain feedback on treatments, and support on living with hyperT.
Diabetes mellitus is a disease in which not enough insulin is produced by the pancreas, or the cat’s body cells do not properly process insulin which the pancreas has produced. Insulin is needed in order to enable the body to process food and to produce energy from it. If this mechanism is faulty, the cat develops hyperglycaemia (high blood sugar), which eventually leads to high sugar levels in the urine (glucosuria). There are two forms of diabetes mellitus, uncomplicated and diabetes with ketoacidosis. Cats with the former may only have mild symptoms, at least in the early stages, but cats with ketoacidosis are usually very ill, and may die if not treated promptly. Obesity in cats, as in humans, is a strong predisposing factor for diabetes. The increase in sugar in the urine causes polyuria (increased urination) and polydipsia (increased drinking). Diabetic cats also tend to lose weight, so to some extent the symptoms of diabetes may resemble those of CRF, although there is one noticeable difference, namely that diabetic cats tend not to lose their appetites – they lose weight despite continuing to eat (this can also be a symptom of hyperthyroidism). More advanced diabetes may also cause lack of appetite, poor coat quality, vomiting and dehydration and occasionally breathing problems. Bladder infections are also relatively common because of the sugar in the urine, and inappropriate elimination may occur. Back leg weakness may be caused by diabetic neuropathy, where the nerves in the legs are damaged by the disease. The Mayo Clinic has information about peripheral neuropathy, including that caused by diabetes. The vet will base the diagnosis on bloodwork, clinical signs, and high levels of sugar in the blood and urine on an ongoing basis. Cats who are stressed by vet visits may sometimes have high blood glucose levels, so this is not necessarily a definite sign of diabetes, it is the ongoing nature of the increased glucose level that is important. Some vets also check fructosamine, which measures concentrations of glucose molecules historically over a period of approximately 2-3 weeks. Lab Tests Online has an overview of the fructosamine test. Cats with ketoacidosis may have elevated BUN and creatinine levels, which in this situation may not necessarily be a sign of CRF, particularly if phosphorus and potassium levels are normal. Diabetic cats also often have dilute urine unrelated to CRF, and the resulting dehydration may also cause increased kidney values. Once the diabetes is under control, the BUN and creatinine levels may improve. Initially the bloodwork may also indicate liver damage, which should improve as the diabetes is brought under control. Cats with ketoacidotic diabetes normally require hospitalisation including IV fluids and insulin therapy, until they are stabilised; thereafter they will be treated as cats with uncomplicated diabetes. Cats with diabetic neuropathy often benefit from Vitamin B12 in the form of methylcobalamin. Jasper's Page has more information on this treatment. Controlling any infection present, such as a urinary tract infection, may make the diabetes easier to control. Uncomplicated diabetes is usually managed by means of insulin injections. Bovine insulin is most similar genetically to feline insulin, and is readily available in the UK; however, in the USA animal-based insulins are often imported from the UK and may be relatively expensive. The insulin is administered once or twice daily, and cats vary in their response, so the amount and the frequency are determined by checking blood glucose levels. This needs to be done every few hours at first and may be done in hospital initially, but gradually the frequency of checks can be reduced to once or twice a day (see monitoring). If the diabetes is properly controlled, the earlier symptoms should disappear. Sometimes diabetic cats can be treated with an oral medication called glipizide instead of injectable insulin. However, only about 30% of diabetic cats respond to glipizide, and cats taking it must be carefully monitored because the drug can damage the liver. In any event, most cats are far easier to inject than to pill. Diabetic cats also require their diet to be monitored. Your vet can advise you on frequency of feeding, but usually cats receiving insulin twice a day are fed half their daily food ration each time; free feeding is not normally appropriate for diabetic cats. Cats receiving glipizide are normally fed several small meals a day. High fibre, high complex carbohydrate diets (such as Hill’s w/d diet) are sometimes recommended for diabetic cats because it used to be believed that they might help to control blood glucose levels. However, cats have a low natural requirement for carbohydrates, and more recent research in fact indicates that higher protein, higher fat and lower carbohydrate diets may be more suitable for diabetic cats. Suitable foods for this approach include Purina DM (Diabetes Management) veterinary formula (not currently available in UK), and kitten foods, which are usually high in protein and fat. Hill's have recently introduced a similar food called Hill's m/d (click on Prescription Diet, then on Cat, then on m/d), which also has a relatively low phosphorus level of 0.7% on a dry matter analysis basis. It is important to try to moderate phosphorus intake for cats with both CRF and diabetes, and if necessary, phosphorus binders will need to be used. Commercial tinned foods low in cereals and added sugars may also work well, but dry foods are unsuitable because they have a high carbohydrate content. Some diabetic cats are so sensitive to carbohydrate that they need less insulin, or in a few cases stop needing it all together, when switched to a low carbohydrate diet. Diet changes should be made gradually if a cat is already taking insulin, and blood glucose levels should be carefully monitored, because sometimes there is a dramatic drop in blood glucose in response to reduced carbohydrate, with a possible risk of an overdose of insulin (see hypoglycaemia). Vetcentric has more information on the high protein, low carbohydrate approach.
Comparison of a low carbohydrate-low fiber diet and
a moderate carbohydrate-high fiber diet in the management of feline
diabetes mellitus (2005) Bennett N, Greco DS, Peterson ME, Kirk
C, Mathes M, Fettman MJ. Journal of Feline Medicine and Surgery
Nov 3 found that the diabetic cats in this study who were fed the low
carbohydrate-low fibre diet were significantly more likely to cease to
need insulin than the cats fed the moderate carbohydrate-high fibre diet. You will probably need to check urine ketone levels using dipsticks (Ketostix, available from pharmacies). Even a trace of ketones is a cause for concern and warrants an immediate vet visit. Urine glucose is only really useful for initial diagnosis – healthy cats do not have glucose in their urine – because it is too imprecise a measure to make proper decisions about insulin dosage. Home Blood Glucose Testing You will also need to monitor your cat's blood sugar levels, and may wish to do this at home using a glucometer (available from pharmacies for use by human diabetics) – home monitoring is much cheaper for you and less stressful for your cat. The blood can normally be taken from the ear using a sterile lancet, and only a tiny amount is required, though many UK vets are unfamiliar with this approach. Generally speaking, a cat is considered regulated if his/her blood glucose consistently remains in the 5-15 mmols/l (US: 100-300 mg/dl) range.
Sometimes cats are started on too high a dose of insulin, which leads to a sudden drop in blood sugar levels, and the body reacts to this by releasing glucagons which raise blood sugar levels again. It thus appears, based on spot checks at the vet's, that the cat requires even more insulin, when in fact the opposite is the case. This is known as the Somogyi Effect. Home blood glucose monitoring gives more accurate results and can help you to avoid such problems.
These websites have information and tips on home blood glucose testing: Veterinary Partner has step by step instructions for home testing with a slide show guide. Pet Diabetes has helpful information. Sugar Cat Punkin Pie's Website Feline Diabetes has information on the Somogyi Effect.
As a general rule, too much insulin is far more dangerous for a diabetic cat than too little, and may cause low blood sugar (hypoglycaemia). Symptoms include weakness, lack of co-ordination, convulsions and coma. The cat should be offered food immediately if still able to eat, or you may need to rub corn syrup or powdered glucose on the gums (in UK you can also buy a human OTC diabetic product called Hypo-Stop); otherwise you should contact your vet urgently. You will need to discuss your treatment programme with your vet in any event following an incident of hypoglycaemia.
Pet Diabetes has information on hypoglycaemia. Gorbzilla also has information on hypoglycaemia.
If you are dealing with both diabetes and CRF, it is more important that the diabetes should be regulated, and in fact once this is achieved, you may find the CRF improves too. Please also see diabetes diagnosis above. People dealing with both diabetes and CRF are sometimes concerned, because it appears that the protein requirements of the two conditions are incompatible, but in fact low protein is not necessarily essential in the treatment of CRF, see Food Composition and Nutritional Requirements and diabetes diet for more information. A dehydrated cat may respond less well to insulin, and many owners have found that once sub-Qs are begun, the insulin seems to work more effectively, sometimes with longer duration than was previously the case. Anecdotal evidence suggests that diabetic cats with CRF do less well on Fortekor (benazepril) than cats with CRF only. General Overviews Cornell University College of Veterinary Medicine has a video covering all aspects of diabetic cat care, including how to give insulin, monitoring your cat, and recognising and treating hypoglycaemia. Cornell University College of Veterinary Medicine good general overview. Washington State University also provides a good overview. Feline Diabetes Message Board FAQs provide detailed answers to frequently asked questions. Gorbzilla has lots of practical information, including information in German.
Support Feline Diabetes Message Board has a very busy message board and a helpful website too. Pet Diabetes List is a list which covers cats and other species; it also has an associated website. Feline Diabetes List is a list for people dealing with diabetes in cats. Feline CRF-FD List is a newer list for people dealing with both CRF and diabetes.
2. Diseases Which May Trigger CRF
PKD is usually asymptomatic, but a PKD cat may exhibit polydipsia (increased thirst). If the disease progresses so far that CRF results, then the usual CRF symptoms will be present. Most cats with PKD appear to develop CRF around the age of 5 - 7 years but seriously affected cats with multiple cysts can fall ill as young as two. Stress or infection can accelerate this disease.
Much depends how badly the kidneys are affected - Harpsie above has PKD yet he is almost 14 years old and not yet in renal failure. He does, however, get frequent kidney infections; these are relatively common in PKD cats because the bacteria can burrow deep into the cysts. Many PKD cats show a slight heart murmur and slightly swollen kidneys before CRF develops, and male PKD cats are often susceptible to FLUTD (feline lower urinary tract disorder).
Quite often PKD cats die from other causes before reaching CRF status. For those where the PKD does develop into CRF, then the usual CRF symptoms will be apparent, and the usual treatments can be used. CRF itself is generally considered not to be a painful disease. Unfortunately, this may not apply to cats who progress to severe end stage PKD: these cats may suffer pain from the cysts growing rapidly and occasionally rupturing. Sadly, nothing can be done for this, but you do need to watch for this occurring in a PKD cat.
The University of California at Davis has identified the gene mutation that causes PKD, and is now offering genetic testing at a cost of US$40 per cat. The test can be run as soon as a kitten is 8-10 weeks old and is almost 100% accurate. You can obtain the sample yourself, it is obtained by non-invasive means so your vet does not need to be involved. Details of how to apply for the test can be found here. You will be sent the results via e-mail. Veterinary Diagnostics Center in Ohio offers a similar test for US$48. In the UK the test is offered by the Animal Health Trust in Newmarket at a cost of £31 or by the University of Bristol (click on PCR Information, then on Polycystic Kidney Disease) for £37 plus VAT. The only other way to diagnose PKD properly is via an ultrasound of the kidneys. Ultrasound is a reasonably accurate method of diagnosis if it is undertaken by somebody skilled in sonography, and ideally with experience of PKD kidneys. Repeated scans may need to be taken if the cat is very young as the cysts may not be visible at that time; it is often hard to detect PKD in cats less than nine months old. Cysts are rare in cats but not all cysts are necessarily PKD; research is still being done in t |
Polycystic
Kidney Disease, known as PKD, is an
autosomal dominant genetic disease of the kidneys which is passed on by one or both
parents - siblings may be unaffected. PKD
affects around 6% of all cats, but appears to be more common in Persian cats,
British Shorthairs and others with Persian
ancestry. One of our Persians, Harpsie (in the washbasin), has PKD. The distinguishing characteristic of PKD is that
cysts are present, usually on both kidneys, and as the cat gets older,
these cysts often increase in size and multiply until eventually kidney
function is diminished. The cat then develops CRF and eventually dies.