Dogs and cats can suffer from either acute or chronic renal failure caused by many different types of illnesses.
Did you know...
In humans, you can donate one kidney to a close relative and live a happy normal life. Should your remaining kidney lose up to 50% of its ability to concentrate urine, you can still appear normal although you may be drinking a bit more and making dilute urine. Standard kidney blood tests can still be normal even at this stage.
In other words, you can loose 3/4 of your total kidney function
and still have normal standard kidney blood tests
What happens in kidney (renal) failure?
Early detection and slowing down the rate of kidney deterioration is the name of the game in both human and veterinary medicine.
Vets are normally unable to offer dialysis and/or kidney transplants for their older patients. Dialysis is performed in people with renal failure to filter out the waste products that the kidney normally places in the urine. When a donor kidney becomes available, they don't need the dialysis any more.
Kidneys place waste products from normal day to day bodily functions in the urine e.g. waste products from protein rich meals (urea and creatinine), phosphate. When we run standard blood tests on advanced kidney failure cases, we see elevated levels of urea (Blood Urea Nitrogen- BUN), Creatinine and Phosphate.
As mentioned before, elevation of these standard blood test results means we are already dealing with less than 1/4 of remaining healthy kidney function.
The good news is the new SDMA blood test has been revolutionary in the early detection of kidney failure, as it detects problems with as little as 25-30% kidney damage - see below.
Kidneys also re-absorb a lot of water that would otherwise escape into the urine. In other words, they make the urine concentrated.
If the kidneys are failing, they are unable to concentrate urine. In other words, the pet makes more urine than normal because the kidneys can't re-absorb the water out of the urine like they did when healthy. More urine going out of the body automatically triggers a chemical release in the brain which makes the pet thirsty. So we see increased thirst and increased volume of urine in renal failure.
Kidneys have powerful protective mechanisms in place which kick into action if problems arise. One of these is a link to the brain to control blood pressure. If the kidneys are not working properly, chemicals are released which elevate the blood pressure in an attempt to improve the flow of blood through the kidney and remove waste products that are building up in the body.
Kidneys are also responsible for sending messages to the bone marrow telling it to make more red blood cells (RBC's) to replace the old ones which are "gobbled up" by the spleen and liver when they are worn out. If there is only 1/4 of normal kidney left, these messages to the bone marrow decrease and quite often, a pet in renal failure is anemic (low numbers of red blood cells). Because RBC's are responsible for carrying oxygen around the whole body, the pet is quite weak and easily fatigued.
Causes of acute renal failure
- Addison's disease
- Cancer e.g. Lyphosarcoma
- Inappropriate use of drugs such as NSAID's and ACE inhibitors
- Inability to urinate e.g. stones (uroliths, FUS/FLUTD), prostate disease
- Poisons: grapes, sultanas, marc -see Grape and Sultana Toxicity
- Reduced blood pressure e.g. anaesthesia
Causes of chronic renal failure
- Normal wear and tear in old age
- High blood pressure
- Genetic e.g. polycystic kidney disease in Cairn Terriers, cats
What are the signs of renal failure?
- Bad breath (halitosis)
- Excess thirst and increased volume urine
- Poor appetite
- Weight loss
How do you diagnose kidney failure?
The earlier kidney disease is detected, the easier it is to treat and the longer the pet lives.
We offer FREE 6 monthly Senior Pet Health Checks. At these checkups we recommend a standard blood screen, SDMA blood test and examination of a urine sample to look at the concentrating ability of the kidneys and check for any infections in the urine.
As with most diseases, early detection and treatment is much more preferable especially for a vitally important organ like the kidneys.
We would rather diagnose kideny failure before clinical signs or standard blood tests indicate its presence. In other words, before the pet is down to its last 1/4 of healthy kidney tissue.That's where the new SDMA blood test has been so good.
This is a new blood test that detects kidney failure when only 25-30% of function is lost. It is helping us to detect kidney failure much earlier and is also a great way to monitor repsonse to therapy.
For all our renal failure cases, we use a Doppler machine to record elevations in blood pressure and measure response to blood pressure lowering medications.
What treatments are available?
Protein Restriction: Good and Bad Points
Failing kidneys are not filtering waste products from meals into the urine. They build up in the body making pets feel off colour and nauseous. Some of these waste oprducts can contribute to further kidney damage.
Standard commercial pet foods don't normally have protein levels high enough to cause this problem.
However, additional protein in the diet, especially meat and meat by-products, will cause further kidney damage and make pets feel ill.
Maintain A Good Bodyweight
Poor body condition results in a poorer prognosis and shorter life span.
It can become a balance between losing weight on restricted protein diets, and maintaining a healthy body weight on commercial foods. Pets with good body condition live much longer, so regular weight checks are important.
One of the main causes of progressive kidney failure is the buildup of phosphorous in the tiny tubes that filter blood and make urine.
If pets have to go back to commerial diets in order to maintain a good body weight, adding in phosophorous binders is very importent e.g. Nicotinamide (10-20mg/kg).
Meat and meat by-products have high levles of phosphorous.
Low phosphorous foods include egg, soy and dairy proteins.
Omega 3 Fatty Acids (n3-PUFA) have been proven to increase the life span of pets with kidney disease.
But they can't just be added to the special kidney diets that some pet are on, as they can dilute and interfere with other nutrients (e.g. protein, phosphorous and potassium) and cause deficiencies.
If they are to be used, then it is best done so with special home made diets.
N.B. Omega 6 Fatty Acids (n6-PUFA) can cause further kidney damage.
Home Made Diets
For a good home made kidney diet, go to BalanceIT.com
They have various diets and sell a recommended supplment to cover any deficiencies in the basic home made diet.
Other standard treatment for acute renal failure cases include:
- Appetite stimulants for cats who are picky eaters e.g. Pericatin (an anti-histamine)
- Force feeding using a stomach tube through which fluids and liquidised renal support diets can be administered
- IV Fluids for very ill pets:
a) Intravenous for short term management in hospital to try and flush the waste products out through the kidneys and correct dehydration.
b) Sub-cutaneous fluid therapy at home using a long-term sub-cutaneous catheter under the skin.
How can success of treatment be monitored?
We like to repeat the SDMA and standard blood and urine tests on a regular basis to measure response to therapy.
Body weight needs to be checked regularly as porr body condition is not good for these patients.
All in all, advanced kidney failure cases can be difficult to treat if pets are down to their last 1/4 of healthy kidneys.
Early detection is much easier to manage. Placing pets on special kidney failure diets prolongs their lives and slows down the rate of deterioration of their kidneys.