Acute Kidney Injury in Dogs

What is acute kidney injury?

Acute kidney injury (AKI) (previously referred to as acute renal failure) is the sudden failure of the kidneys to perform normal filtration duties. This condition is not the same as the much more common form of kidney failure called chronic kidney disease (CKD). 

AKI leads to accumulation of toxins and other metabolic wastes in the bloodstream, dehydration, electrolyte imbalances, and disturbances in the acid-base balance of the blood. AKI is potentially reversible if diagnosed early and treated aggressively. 

What are the clinical signs of AKI?

The clinical signs of AKI usually have been present for less than one week, and may include:

• Sudden anorexia (not eating)
• Listlessness
• Vomiting (the vomited material may have blood in it)
• Diarrhea (that may contain blood)
• A strange breath odor
• Ulcers in the mouth
• Low blood pressure
• Rapid or slower than normal heart rate 
• Seizures
• Changes in urine production (some dogs urinate more frequently and others may not produce any urine
• Some dogs may drink more than normal

There may be a recent history of ingestion of a toxin (e.g., antifreeze, grapes, raisins) or of recent trauma, surgery, or illness. Many dogs are in shock by the time they reach the veterinary hospital. The veterinarian will frequently find enlarged and painful kidneys during the physical examination.

What causes AKI?

There are numerous causes of AKI. Some common causes include:

• Ureteral or urethral obstruction (i.e., the dog cannot urinate)
• Antifreeze poisoning (ethylene glycol toxicity)
• Systemic shock
• Congestive heart failure
• Liver failure
• Hypotension or low blood pressure
• Clotting disorders
• Ingestion of drugs such as NSAIAs (nonsteroidal anti-inflammatory analgesics) or certain antibiotics
• Insect or snake bites
• Ingestion of heavy metals such as lead, mercury, arsenic, or thallium
• Ingestion of toxic plants, especially lilies
• Trauma, burns, or heatstroke
• Ingestion of rodenticides (rat poison)
• Pyelonephritis (a bacterial infection of the kidney)
• Ingestion of grapes and/or raisins
• Infections such as Lyme disease

How is AKI diagnosed?

Diagnosis is based on medical history, clinical signs, and the results of blood and urine tests. Other diagnostic tests may include urine culture testing, acid/base balance testing, abdominal radiographs (X-rays), abdominal ultrasound, fine needle aspiration (sampling the kidney using a long needle), surgical biopsy of the kidneys, and possibly magnetic resonance imaging (MRI) or computed tomography (CT).

What is the treatment for AKI?

Treatment is focused on removing the circulating toxins as quickly as possible and restoring electrolyte balance. This goal is usually accomplished by administering intravenous fluids for 24 to 96 hours (1 to 4 days). 

Rarely, peritoneal dialysis and hemodialysis may be performed (purifying the blood of toxins, like a person waiting for a kidney transplant might receive). If toxin exposure or a drug reaction is suspected, it is recommended that the dog’s stomach be emptied immediately and then activated charcoal should be administered to prevent the dog from further absorbing toxins.

Nutritional support may be required in dogs with persistent or uncontrollable vomiting. Other supportive measures include medications to control vomiting, treat diarrhea, and prevent gastrointestinal ulceration. Diuretics and certain blood pressure medications may also be used to increase blood flow to the kidneys. 

Your veterinarian will recommend an aggressive treatment plan to give your dog the best chance of recovering from AKI.

What is the prognosis for a dog diagnosed with AKI?

The initial prognosis is guarded for all cases of AKI, with a mortality rate of approximately 60% (when analyzed across all causes of AKI). The long-term prognosis for recovery depends on the amount of kidney damage that has occurred. The kidney has very little capacity to regenerate or heal itself, leading to the guarded prognosis. Your veterinarian will provide you with a more accurate prognosis based on your dog's clinical signs, results of laboratory tests, and individual condition.