Acute renal failure (ARF) in dogs can be tricky to diagnose because many of its signs mimic those of other ailments. However, given time and a willing owner, veterinarians have the skills and tools necessary to arrive at a definitive diagnosis. A dog with ARF that is severe enough to cause noticeable signs usually arrives at the veterinary clinic with a fairly normal hair coat and in good body condition. The owner typically brings his dog in because it has become weak, listless, lethargic, depressed and often dehydrated, despite drinking lots of water and urinating more frequently and in higher amounts than usual. The dog may have also developed strange or very bad breath.
The veterinarian will take a thorough history from the owner about his dog’s general health, vaccination status and symptoms, and also about its potential access to toxic substances including antifreeze over the past few weeks. The vet will examine the dog from nose to tail tip. She may detect an elevated heart rate (tachycardia) or respiratory rate (tachypnea). The initial database usually includes taking blood and urine samples and conducting a complete blood count, serum biochemistry profile and urinalysis, all of which are routine tests that are easy to conduct and are relatively inexpensive. The test results in dogs with acute renal failure may reveal elevated blood urea nitrogen (BUN), creatinine and phosphorus levels, abnormally low urine specific gravity and maybe evidence of a urinary tract infection or obstruction. High levels of circulating BUN, creatinine and phosphorus are caused by the kidneys’ inability to properly filter toxic waste products from the blood and flush them out in urine. Low urine-specific gravity means that the kidneys aren’t able to reabsorb water and concentrate urine normally, which makes it overly dilute, contributing to the dog’s dehydration, despite a high water intake.
More advanced blood tests can be conducted to detect the presence of ethylene glycol antifreeze and to detect Leptospira infection. Direct or indirect blood pressure tests are common. Abdominal ultrasounds and radiographs (X-rays) can reveal changes in kidney size, tissue or structure, cysts, tumors, urinary tract obstructions and other abnormalities.
If the initial diagnostic procedures point to acute renal failure, the dog may need to be hospitalized. A urinary catheter may be placed so that the medical team can monitor the dog’s urine output. The dog probably will be put on intravenous fluids to correct hydration and flush toxins into the urine. Fine needle aspirate samples of kidney tissues can be taken, with or without ultrasound guidance, so that the veterinarian can evaluate the kidneys’ cellular structure under magnification. This is especially useful for determining whether lymphosarcoma is responsible for any noticeable kidney enlargement. Biopsies can also be taken of kidney tissue and submitted to a pathology laboratory for assessment.
Urinary tract infections (UTIs) are common in dogs with kidney disease. Resolving those infections can help improve kidney function and alleviate discomfort in some dogs.