May 1, 2012
The first step in controlling a patient’s kidney or heart condition is a reliance on the owner’s detection of a clinical problem. Cardiology and kidney specialists suggest preparing clients whose pet has a high risk of disease before symptoms begin–even running blood work or genetic testing if it applies.
Information that veterinarians provide to clients will help the owners recognize disease symptoms and increase compliance with veterinary directions when managing the disease. Two-thirds of dogs and more than half of cats suffering from cardiac disease have concurrent diseases.
Because a large number of kidney and heart disease patients are of an advanced age, it’s not uncommon for a patient being treated for one disease to develop the other, a situation that takes a vigilant veterinarian and dedicated owner to manage.
“Once we have a diagnosis and the client understands the disease and necessity to follow up, the biggest obstacle is the owner’s financial commitment,” says Megan King, VMD, Dipl. ACVIM (cardiology) of the Center for Animal Referral and Emergency Services in Langhorne, Pa. “For much of heart disease there may not be a substantial cost, but as the pet deals with more advanced disease and congestive heart failure, the cost can become more significant, especially when considering kidney disease as well.”
Because of financial hurdles, veterinarians may be restricted in treating some of their heart and kidney disease patients. This factor makes prevention a big factor in proactively serving patients’ needs. Initiating a blood workup at a certain age or for specific breeds can be a lifesaver that catches disease at a more medically and financially manageable stage.
“Disease can be captured early with annual lab work,” says Larry Cowgill, DVM, Ph.D., Dipl. ACVIM, a professor of small animal medicine at the University of California, Davis, School of Veterinary Medicine. “After age 5, particularly with cats, monitoring kidney disease must increase, as the incidence of disease continues to increase with age. Currently, laboratory perimeters aren’t as accurate as we’d like, so the International Renal Interest Society (IRIS) is working to develop a staging system for veterinarians. Also, the International Renal Veterinary Pathology Initiative (IRVPI) developed a national registry for glomerulonephritis, caused by an inflammation of the internal kidney structures called glomeruli, so veterinarians can share new information.”
Veterinarians know the symptoms of kidney disease all too well: increased thirst and urination, vomiting, anorexia, lethargy and with 40 percent or higher of older cats diagnosed with kidney disease, it’s the first suspect. Dogs have about a 7 percent prevalence rate, and disease is often not detected in them until its advancement allows for little more than palliative care.
If environmental components can be eliminated as the cause of a presenting animal’s symptoms, the underlying cause of disease must be detected before maintenance instructions are given.
“Some supplements are under investigation for their ability to be helpful in disease maintenance,” says David Polzin, DVM, a nephrology and urology associate at the University of Minnesota.
“Omega-3, antioxidants and calcitrol have shown some value for diet maintenance, which would be recommended for animals in second-, third- and fourth-stage disease. The best maintenance remains veterinary prescribed diets and not those found in grocery stores.”
For dogs especially, promoting the prevention of kidney disease from environmental factors may help decrease the patients’ likelihood of getting the disease, Dr. Cowgill says.
“Depending on your geographic location, Lyme disease and leptospirosis may play a role in the incidence of kidney disease,” Cowgill says. “Non-geriatric cats have a higher incidence of kidney disease because of chronic and acute ureteral obstruction from kidney stones. These skewed perceptions don’t allow the profession to be on the same page with cause of disease, prevalence and treatment. A national registry would improve maintenance and treatment options.”
The mission of IRIS is to help veterinary practitioners better diagnose, understand and treat renal disease in cats and dogs.
One of the organization’s main objectives is to establish an internationally recognized set of guidelines on the diagnosis and assessment of progression of renal disease in small animals. IRIS’ board has developed a treatment recommendation for chronic kidney disease. These guidelines are reviewed annually and can be found at Iris-Kidney.com.
UC Davis, until its recent postponement of the procedure, performed about 24 feline kidney transplants annually, taking the treatment of kidney disease to the highest level after animals reach the final stages of disease. Veterinarians know they can combine drugs and diet to manage the disease, and if these clients make their way to a specialist, they tend to be willing to go the extra mile to financially and emotionally provide for the pet, but what happens to the animal once a second diagnosis is made?
“Education is extremely important,” Dr. King says. “If you communicate with your clients and give them the information they need to prepare them to do what is needed for the pet, they are likely to be more compliant, but as the diagnosis worsens or disease progresses, the veterinarian needs to do more to prepare the client: give step-by-step directions for administering a special diet, exercise regulations and expectations from the pet.”
Dogs tend to be easier to diagnose because of their lessened ability to mask discomfort and reliance on the owner for elimination and closer human interaction.
“In most situations, a detailed physical examination, auscultation, thoracic radiographs, ECG and complete bloodwork will help get a baseline for the patient’s cardiac disease,” King says. “Cats continue to challenge veterinarians as they can have a relatively normal auscultation or radiographs and still have underlying heart disease. Cats can require an echocardiogram to determine cardiac disease.”
Cardiovascular disease is the best predictor of death in patients with end-stage renal disease, accounting for almost half of deaths. Patients with varying degrees of chronic kidney disease also have a markedly increased risk of morbidity and mortality from cardiovascular disease, including coronary heart disease.
“There are different drug therapies for treating animals with heart disease depending on the underlying disease type and severity,” King says. “But the mainstay of therapy once an animal goes into congestive heart failure is with diuretics and angiotensin converting enzyme inhibitors. There are additional medications for arrhythmias, hypertension or other problems. A new medication called Pimobendan, manufactured by Boehringer Ingelheim, has really helped a lot of cardiac patients. This medication has a phosphodiesterase benzimidazole-pyridazione inodilator with a potent positive intropic and vasodilatory effect.”
Chronic renal dysfunction alone is a risk factor on its own for the development of coronary artery disease and heart disease. Chronic kidney disease is also associated with an adverse effect on prognosis from cardiovascular disease. This includes increased likelihood of death after an acute coronary syndrome.
Genetic testing allows veterinarians to proactively test for the certain types of heart disease in the specific breeds it targets, such as mitral valve disease in Cavalier King Charles Spaniels, which is the cause of death in 75 percent of the breed; polycystic kidney disease in Persian cats; and hypertrophic cardiomyopathy in rag dolls and Maine coons.
Genetic testing offers an opportunity to drastically reduce the incidence of disease by eliminating those showing markers for disease from the breeding pool, and treating them in stage 1 to provide them with the best outcome.
Veterinarians can prevent significant onset of kidney disease through blood tests; they know older cats are at the highest risk and catching the disease in early stages will allow for better maintenance. Spaniels under the age of 5 should not be bred and those 5 and older that have been diagnosed with the disease shouldn’t be bred in an effort to eradicate the disease prevalence in the breed.
“The reasons for disease frequency are numerous,” Polzin says. “But the reason disease detection is delayed is simple. Owners don’t approve blood work in cats and breeders don’t follow testing protocols.”
Veterinarians’ role in preventing disease onset is a proactive approach to disease maintenance, King says.
“Veterinarians should recommend genetic testing in Maine coons and ragdolls,” King says. “Over time using these genetic tests helps guide breeders’ decisions in order to reduce the prevalence of the disease in these breeds. These tests still have limitations.
“The heart disease has a variable penetrance so not all cats with the mutation will actually get the disease. We also know there are many forms of the disease, so despite being negative for the mutation, cats can still develop underlying cardiac disease.
“Despite amazing advancements, we are just at the tip of the iceberg and these purebred cats are only a small portion of the overall cat population affected by heart disease.”
Mary Nabity, DVM, Dipl. ACVP, a clinical assistant professor and Ph.D. candidate at Texas A&M University, is working on Morris Animal Foundation-funded research that can develop an early detection test for chronic kidney disease.
Dr. Nabity is evaluating the urine proteins in mixed-breed dogs in search of novel biomarkers of early tubular damage and renal disease progression using two proteomics techniques – 2-dimensional gel electrophoresis and surface-enhanced laser desorption/ionization (SELDI).
“We want to develop a user friendly test that can be used in-house or sent to a lab for analysis,” Nabity says. “Through a better testing method, we can expand life expectancy of animals with kidney disease. Now 65 to 75 percent of an animal’s kidney function can be wiped out before the disease is even detected.”
Leslie Lyons, Ph.D., a geneticist with UC Davis, says the ultimate maintenance for animals with concurrent kidney and heart disease will be gene therapy.
“Some gene therapy is already in use in the profession,” Dr. Lyons says. “However, we are a ways away from using it clinically to treat kidney or heart disease. Once something is finalized, it will be the gold standard of treatment.”
Two-thirds of dogs and more than half of cats with cardiac disease have concurrent diseases that might influence their diet selection, said Lisa M. Freeman, DVM, Ph.D., Dipl. ACVN, a nutritionist at Cummings School of Veterinary Medicine at Tufts University in North Grafton, Mass.
“Some dogs with chronic heart failure might also have chronic renal failure and this might necessitate protein restriction,” Dr. Freeman says. “However, patients with cardiac disease alone should not be protein-restricted. Cats with hypertrophic cardiomyopathy might also have concurrent struvite urolithiasis. These cats need a diet that is sodium-restricted but also has nutritional modification to reduce the risk of struvite urolith formation.”
Specialists say the recommended diet for animals with cardiac disease alone is not universal but in general, the nutrients of concern in cardiac patients are calories, sodium, chloride, protein, potassium and magnesium. But deciding on a diet isn’t clear-cut. Clinical signs, laboratory parameters and food preferences all affect diet selection.
Animals diagnosed with kidney disease that have now also been diagnosed with heart disease may have been switched by the veterinarian from a non-monitored diet to a therapeutic diet that manages their kidney disease.
On a case-by-case basis, these newly diagnosed animals should be evaluated for their specific benefits for altering their diet again to avoid food aversions. Low-protein diets are an essential tool in managing disease progression in kidney disease patients to generate fewer nitrogenous wastes, but decreased protein may have a derogatory effect on animals also suffering from heart disease as low protein may contribute to muscle loss or cardiac cachexia.
“As chronic heart failure becomes more severe, more significant sodium restriction may allow lower dosages of diuretics to be used to control clinical signs,” King says. “Once the patient is stabilized with medication, a gradual change to a new diet can be made.”
The goal is to extend the quality of life of patients with kidney and heart disease without propelling disease, causing anorexia or assigning a diet that isn’t palatable. In some cases, dietary supplements may be recommended in addition to medication and diet control.
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