Adrienne is a certified dog trainer, behavior consultant, former veterinarian assistant, and author of Brain Training for Dogs.
Diagnosis of Chronic Kidney Disease in Senior Dogs
One of the earliest signs of kidney failure in senior dogs is increased drinking. This increased thirst, medically known as polydipsia, is often unexplainable—the weather is not too hot, the dog has not exercised, the dog has not eaten foods that trigger thirst, nor is he on medications that increase drinking.
This increase is triggered by special sensors in the brain. When waste products accumulate in the dog's body, the sensors basically realize that the dog's blood is too concentrated. This triggers the dog to drink more. Because what goes in must come out, soon the excessive drinking will transform into increased urination (polyuria), or worse, eliminating in the night or wetting the bed.
In a healthy dog, kidneys help filter toxins, removing them from the bloodstream and discarding them in the urine. When the kidneys are not functioning properly, they cannot perform these tasks well, and the resulting urine is very dilute as the kidneys are not removing toxins and waste from the body as they are supposed to. When this happens, toxins build up and the body reacts with vomiting and diarrhea in an effort to remove these toxins.
In dogs, kidney disease is often part of the aging process. Indeed, it's often thought to be the result of wear and tear of the kidney tissues over time. In small dogs, early signs of kidney failure can be seen around 10 to 14 years of age; whereas, in larger dogs they can become noticeable as early as seven years of age.
The Issues With Routine Kidney Tests in Dogs
Upon seeing the vet, the first and foremost diagnostics include a urinalysis and blood tests to determine waste products in the blood.
The urine test often encompasses a urine specific gravity (USG) measurement where the concentration of the urine is tested. In kidney failure, the reading will reveal dilute urine of a gravity close to distilled water.
- A dog's normal specific gravity measurement ranges between SpG: 1.020 to 1.040
- A dog with kidney failure will have an SpG of about 1.008 to 1.012
A low urine specific gravity is one of the earliest signs of kidney failure, suggesting that about two-thirds (67%) of kidney function has been impaired. Additionally, a urine test may show an increase in protein in the urine which can also be suggestive of decreased kidney function.
The blood test looks at blood urea nitrogen (BUN) and creatinine levels.
- In normal dogs, BUN levels are rarely higher than 25 to 30 mg/dL. Dogs with renal failure instead often have BUN levels of 90mg/dL or more.
- Creatinine in normal dogs is usually less than 1.0 mg/dL, but in dogs with kidney issues may raise up to over 8 mg/dL.
When a dog presents with a low specific gravity and high levels of BUN and creatinine, it's suspected that about three-fourths (75%) of the kidney function is compromised. Low specific gravity, high levels of BUN and creatinine, and high levels of phosphorus are indicative of severe kidney failure with about 83 to 87% of kidney function impairment.
The problem with diagnosing kidney problems in dogs is that dogs often show symptoms only once 75% of the kidneys have been damaged and clues about this organ malfunctioning appear only once the damage has been done. According to VCA Animal Hospital, a dog with marginal kidney function may show normal levels of BUN and creatinine (the only sign may be urine with low specific gravity), but should major assault on the kidneys occur, such as in the case of surgery or disease, kidney failure may take place and send those blood test values up quickly. Early detection of dog kidney disease is difficult, but there are fortunately some innovative options underway.
Tests for Early Detection
Early detection of kidney disease is very helpful because in its earliest stages, kidney deterioration can be potentially reversed. The problem with early detection is that dogs do not show any signs until the kidneys are already compromised.
One innovative test is the E.R.D.-Screen™ Urine Test from Heska Corporation. This test is capable of detecting albumin in urine 30 times better than regular dipsticks and prior to BUN/Creatinine showing problems. In humans, it was discovered that small amounts of albumin (microalbuminuria) in the urine were reliable predictors of impending problems. The same phenomenon was detected in dogs, leading to the creation of the ERD screen test by Heska. The test is a simple 5-minute in-hospital test
Another innovative test is the SDMA test by IIDEXX capable of detecting the early stages of kidney disease months or even years earlier than traditional tests. Also known as " symmetric dimethylarginine," this test is based on scores, and a persistent increase in SDMA above 14 µg/dL is suggestive of reduced renal function. According to an article by DVM360, IDEXX representatives claim that SDMA is a biomarker that's highly specific to kidney damage and impairment affecting just 25 to 40 percent of the kidney can be detected. IDEXX is offering this test for free in routine chemistry profiles.
As seen, these innovative tests can be quite helpful in detecting early stages of kidney disease before symptoms arise. With early detection, there may be better chances for recognizing problems and granting a better prognosis. For a guide on the grading of acute kidney injury in dogs and cats, visit the International Renal Interest Society website.
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2015 Adrienne Farricelli
Adrienne Farricelli (author) on August 30, 2015:
Thanks Jodah, my dogs are senior as well and was researching how to detect early kidney disease as my male may have to have a surgery soon. Back in the days, at the vet hospital, there were none, so it's good to hear in these years they have made advances.
John Hansen from Queensland Australia on August 25, 2015:
Interesting and helpful article. We have three dogs (one big and two mall) and all are around 10 years old. So far they seem fine but it's good to know what to look for.