Kidney disease in dogs has many causes, from viral infections and poisoning to cancer. It can develop insidiously, with subtle, easy-to miss symptoms at first. Acute kidney failure is harder to miss because the dog will go downhill very quickly. One of the easiest ways to detect kidney disease is by a simple annual blood test. Your vet can easily tell you if there are early signs of kidney failure.
There are two basic types of kidney (renal) failure. Acute renal failure (ARF) is often caused by ingestion of poisons such as antifreeze and rat poison. ARF symptoms manifest very quickly. Chronic renal failure (CRF) usually progresses slowly, with no symptoms in the early stages. CRF can be caused by cancer, leptospirosis parasites and congenital abnormalities of the kidney. While most common in middle-aged and senior dogs, CRF can affect young dogs and puppies.
The kidney's primary purpose is to filter out the near-constant stream of toxins, both ingested and natural waste products produced by bodily functions. Drinking water keeps the kidney tissues flushed of these toxins. Anything that scars or swells the kidneys impedes the flushing process and allows toxic build-up. Chronic dehydration, even with healthy kidneys, has the same effect by not cleansing the kidneys.
The first symptoms you will probably notice in any type of kidney disease is excessive thirst and urination. In an effort to rid her body of toxins, the dog will drink copious amounts of water. Occasionally swelling or scarring in the kidneys will prevent her from urinating, or make it very painful to do so. When this happens the dog may frequently drink a large amount of water, then promptly vomit it back up.
As kidney functioning declines, she will feel ill and lose her appetite. She may become depressed and lethargic. Smell her breath: there may be a sharp, ammonia-like odour. At this point she is critically ill and needs immediate medical attention.
Whether symptoms advance slowly, or manifest suddenly, the dog needs to be taken to your veterinarian. If possible, bring a urine sample with you. It's important not to restrict a very thirsty dog's access to water. Even if this makes her incontinent, she is doing her best to keep her kidneys hydrated.
The first test your veterinarian will do is a blood test to check blood urea nitrogen (BUN) and creatinine levels. These are indicators of kidney functioning. While BUN naturally fluctuates, both high BUN and creatinine levels mean the kidneys are diseased. Other findings such as high calcium and phosphorus levels add to the clinical findings and help the clinician map out a treatment plan.
Low urine specific gravity and excess protein in the urine indicates kidney disease. Additional laboratory tests can point to the specific cause of the renal failure.
If laboratory findings suggest possible cancer, your veterinarian may want to do an ultrasound of the kidneys. Organ tumours are usually quite clear on ultrasound images, and may be further confirmed with a fine needle biopsy to check for signs of cancer cells.
In either chronic or acute kidney failure, the kidneys usually do not heal and are left permanently damaged. However, with dietary management, it's usually possible for a dog with kidney disease to live a long, healthy life. Your veterinarian should have prescription foods available.