Kidney Failure in Dogs
by: Laura McLain Madsen DVM
What is kidney failure?
Kidney failure in dogs (or renal failure) means that the kidneys are incapable of maintaining their life-sustaining functions. Kidney failure can be categorized as sudden (ARF, acute renal failure; also called AKI, acute kidney injury), long-standing (CRF, chronic renal failure; also called CKD, chronic kidney disease), or “acute-on-chronic” (meaning a sudden worsening of a chronic problem).
What do the kidneys do?
The dog's kidneys are responsible for filtering toxins out of the bloodstream, which they excrete into the urine. Urine made by the kidneys flows through the ureters to the bladder and then out from the body through the urethra. The kidneys also regulate levels of electrolytes in the body and signal the bone marrow to manufacture red blood cells.
What causes kidney failure in dogs?
There are many causes of kidney failure, and often the exact cause can’t be pinpointed. Possible causes include:
• Ethylene glycol (EG), a component of car antifreeze, windshield de-icers and brake fluids. Unfortunately EG is sweet-tasting so dogs lap it up. Just a small amount can be poisonous. In the first stage of poisoning, the dog acts “drunk”—wobbly and disoriented. After 12 hours the dog acts normal again, but then after another 12-36 hours the dog becomes very sick from acute kidney failure.
• Grapes and raisins. Some dogs eat grapes and raisins without a problem but other dogs have an idiosyncratic (unpredictable) response and develop acute kidney failure. Cases of kidney failure have been reported after dogs have consumed just a few ounces of grapes or raisins.
• Cholecalciferol-containing rat bait. Most rat and mouse baits contain other active ingredients, but some contain cholecalciferol, which alters the metabolism of calcium and phosphorous in the body leading to acute renal failure.
• Non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs, including veterinary medications (Rimadyl® [carprofen], Deramaxx® [deracoxib], Metacam® [meloxicam], Previcox® [firocoxib], Etogesic® [etodolac]) and human medications (Advil® or Motrin® [ibuprofen], Ansaid® [flurbiprofen], Mobic® [meloxicam], Aleve® [naproxen], Voltaren® [diclofenac], Celebrex® [celecoxib]) can cause kidney failure, especially when overdosed, as well as stomach ulcers.
• Conditions which decrease blood flow to the kidneys: heat stroke, dehydration, hypotension (low blood pressure, especially with general anesthesia), heart failure.
• Congenital problems (birth defects): kidney cysts, malformed or missing kidney.
• Obstruction of urine flow: stones or tumors.
• Infections: bacterial kidney infection (pyelonephritis), leptospirosis (water-borne bacteria.
What are the symptoms of kidney failure in dogs?
Symptoms vary depending on whether the case is acute or chronic. In ARF, the dog will be lethargic and not wanting to eat. There may be vomiting, and either an increased or decreased thirst. Urination may be increased (polyuria), decreased (oliguria) or absent (anuria).
The symptoms of CRF come on more gradually. Usually dogs drink and urinate excessively. They may also have weight loss, lethargy, loss of appetite, and intermittent vomiting. Seizures or behavioral abnormalities are occasionally seen.
How is kidney failure in dogs diagnosed?
Kidney failure itself is easily diagnosed on the basis of routine blood and urine testing, but the exact cause of the failure may require additional testing. Specific values that your veterinarian will look at on lab testing are:
• BUN (blood urea nitrogen) and creatinine. Urea and creatinine are byproducts of metabolism and are normally excreted by the kidneys into the urine. Levels of these chemicals build up in the bloodstream when the kidneys are failing. When the BUN and creatinine are elevated, it is termed azotemia. Azotemia won’t be seen until 75% of kidney function is lost, so there can be significant damage to the kidney that will not be apparent on blood tests.
• Urine specific gravity (USG). The USG is an indicator of how concentrated the urine is. It is measured with an instrument called a refractometer and the values range from 1.001 (extremely watery) to over 1.040 (very strong). The kidneys continually adjust the specific gravity based on the body’s water needs.
For example, if a dog drinks a lot of water the kidneys will “dump” the extra water into the urine and the USG will be low. If the dog is dehydrated from illness or exercise, the kidneys will conserve water and the USG will be high. The USG must be interpreted in conjunction with the BUN, creatinine, and level of dehydration of the pet.
• Electrolytes. Sodium, potassium and chloride levels can be abnormal in kidney failure. Especially dangerous is high potassium because it can cause serious heart arrhythmias.
• Red blood cell count. Packed cell volume (PCV) and hematocrit (HCT) measure the red blood cell count. Anemia (low red blood cell level) can be seen in CRF because the kidneys aren’t signaling the bone marrow to make red cells. Anemia causes weakness and pale gums.
• Phosphorus and calcium. The kidneys also play a role in regulation of phosphorus and calcium metabolism, so the levels of both can be increased in renal failure.Other diagnostic tests that may be used include:
• X-rays: to look at the shape of the kidneys and detect kidney or bladder stones.
• Ultrasound: to evaluate the kidneys and urinary tract for tumors or other abnormalities.
• Blood pressure: often elevated with chronic kidney disease.
• Urine culture: to detect urinary tract infection.
• Titer tests: to diagnose leptospirosis or other infections.
• Ethylene glycol test: to determine if the dog ingested a toxic level of EG. The test can be run 30 minutes to 12 hours after ingestion.
What is the treatment?
Treatment depends on whether the kidney failure in dogs is acute or chronic. Acute kidney failure is best treated in the hospital. Your veterinarian will place an intravenous catheter and infuse IV fluids at a rapid rate to maintain blood flow to the kidneys and flush the urinary tract.
Usually a urinary catheter will be placed into the bladder so that the urine production can be monitored. The amount of urine made by the kidneys should equal the amount of IV fluids entering the patient. If the kidneys are completely shutting down and not producing urine, treatment will need to be very aggressive.
There is a specific antidote for ethylene glycol antifreeze poisoning, called Antizol-Vet® (fomepizole, 4-methylpyrazole). If Antizol-Vet® treatment is started within eight hours of the dog drinking antifreeze, the prognosis is good. However, if the critical eight-hour window for treatment is missed, the prognosis rapidly worsens.
Other medications which may be used in acute cases include antibiotics (penicillin, amoxicillin, or doxycycline for leptospirosis), anti-nausea medications such as Cerenia® (maropitant) and Reglan® (metoclopramide), antacids like Pepcid® (famotidine), stomach protectants like Carafate® (sucralfate) and pain medications. If the kidneys aren’t producing adequate amounts of urine, medications which may help “jump start” urine production are Lasix® (furosemide), mannitol, and dopamine.
The treatment of chronic kidney failure in dogs mainly aims to prevent ongoing damage to the kidneys and to maintain a good quality of life. A prescription diet is usually recommended which is low in phosphorus, moderate to low in protein, and high in anti-inflammatory fatty acids. Other treatments that may be recommended on a case-by-case basis include:
• Stomach protectants, such as Pepcid® (famotidine) or Prilosec® (omeprazole).
• Phosphorous binders if the blood phosphorus level is too high, such as aluminum hydroxide (Amphogel® or Alternagel®), calcium carbonate/ chitosan (Epakitin®), lanthanum carbonate(Fosrenol®).
• Calcitriol, a medication which regulates calcium and phosphorous metabolism.
• Antibiotics if a kidney infection is present.
• Blood pressure medications (amlodipine [Norvasc®], enalapril [Enacard®], benazepril [Lotensin®]) if hypertension is present.
• Potassium supplementation if the blood potassium level is too low, such as potassium gluconate (Tumil-K®).
• Erythropoietin (Epogen®) or darbepoetin (Aranesp®) if anemia is present. These are synthetic hormones given by injection to stimulate the bone marrow to manufacture red blood cells.
What about dialysis or transplant like in people?
Some specialty veterinary centers have the capability to perform hemodialysis, a procedure to filter the blood until kidney function is regained. Very few veterinary hospitals perform kidney transplants in dogs; extensive pre- and post-transplantation testing and treatment are required.
What is the prognosis?
The prognosis varies depending on the cause of kidney failure in dogs and on how many kidneys cells remain after the injury. Kidney tissue can regenerate to some extent. In some cases, if ARF is caught early and treated aggressively, dogs can fully recover and lead a long and happy life.
Unfortunately, antifreeze has a very poor prognosis; once the kidneys start to fail from antifreeze poisoning it is usually fatal. The prognosis for chronic kidney failure is guarded for the short-term and poor for the long-term. Treatment can improve the dog’s quality of life, but isn’t going to reverse the damage that has already been done.
How can I prevent kidney failure in my dog?
Many cases of kidney failure in dogs aren’t preventable. However, you can prevent your dog from having access to grapes, raisins, medications and antifreeze. If you live in an area with leptospirosis your dog can be vaccinated against the infection. In addition, many veterinarians recommend annual wellness blood tests. Screening tests could detect early kidney disease before it becomes severe enough to cause symptoms.
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