Understanding Kidney Disease in Dogs
The kidneys perform dozens of essential functions in a dog's body: filtering waste products from the blood, regulating fluid and electrolyte balance, controlling blood pressure, and producing hormones that stimulate red blood cell production. When kidney function declines, these processes are disrupted, and the effects can range from subtle early signs to life-threatening emergencies.
Kidney disease in dogs is broadly divided into two categories: acute kidney injury (AKI) and chronic kidney disease (CKD). Understanding which type your dog has — and what caused it — is the first step towards effective management.
Acute Kidney Injury Versus Chronic Kidney Disease
Acute kidney injury develops rapidly, often over hours or days, and is typically triggered by a specific event such as a toxic exposure, infection, or severe dehydration. The kidneys can sometimes recover if the underlying cause is treated quickly and supportively. AKI is a medical emergency requiring hospitalisation and intravenous fluid therapy.
Chronic kidney disease, by contrast, develops slowly over months or years. Kidney tissue is gradually and irreversibly lost. Most dogs with CKD are managed rather than cured, with the aim of slowing progression and maintaining quality of life for as long as possible. CKD is far more common in middle-aged to older dogs, though it can occur at any age.
IRIS Staging: How Vets Classify Kidney Disease
The International Renal Interest Society (IRIS) provides a globally recognised staging system for canine CKD, using blood creatinine and SDMA levels as the primary markers. The staging system runs from Stage 1 (earliest, mildest) through to Stage 4 (most severe), and is further refined by substaging for blood pressure and proteinuria (protein in the urine).
- Stage 1: SDMA above 18 micrograms per decilitre or creatinine below 125 micromoles per litre. Kidney function is reduced but clinical signs are often absent.
- Stage 2: Creatinine 125–250 micromoles per litre. Mild azotaemia (accumulation of waste products). Some dogs remain well; others show increased thirst and urination.
- Stage 3: Creatinine 251–440 micromoles per litre. Moderate azotaemia. Dogs often show weight loss, reduced appetite, vomiting, and lethargy.
- Stage 4: Creatinine above 440 micromoles per litre. Severe azotaemia. Uraemic signs including vomiting, mouth ulcers, seizures, and profound weakness become apparent.
Staging is important because it guides treatment decisions, frequency of monitoring, and prognosis. Dogs diagnosed at Stage 1 or 2 often live comfortably for years with appropriate management.
SDMA: Earlier Detection Than Creatinine Alone
Symmetric dimethylarginine (SDMA) is a biomarker that rises earlier than creatinine when kidney function begins to decline. While creatinine does not increase above the reference range until approximately 75% of kidney function is lost, SDMA can become elevated when only around 40% of function has been lost.
SDMA is now included in many routine blood panels and is part of the IRIS staging criteria. Earlier detection means earlier intervention, which can meaningfully slow the progression of CKD. If your dog's SDMA is flagged as mildly elevated on a blood test, do not dismiss it — this is clinically significant even when creatinine remains normal.
Common Causes of Acute Kidney Injury in Dogs
NSAIDs: The Most Common Iatrogenic Cause
Non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam, carprofen, and ibuprofen are among the most frequent causes of drug-induced, or iatrogenic, AKI in dogs. NSAIDs reduce the production of prostaglandins, which play a vital role in maintaining blood flow to the kidneys. In dogs that are already dehydrated, in heart failure, or under general anaesthesia, NSAID use can cause a rapid and severe reduction in renal perfusion.
Human NSAIDs such as ibuprofen and naproxen are far more toxic to dogs than licensed veterinary formulations and must never be given to dogs. Even veterinary NSAIDs should always be used with access to fresh water, never in combination with other NSAIDs or corticosteroids, and with caution in dogs with pre-existing kidney concerns.
Leptospirosis: An Infectious Cause of AKI
Leptospirosis is a bacterial infection caused by Leptospira species, spread through the urine of infected animals — most commonly rats, but also cattle, foxes, and other dogs. Dogs acquire the infection through contact with contaminated water, soil, or mud, which makes working dogs, dogs walked near rivers or canals, and those in rural environments particularly vulnerable.
Leptospirosis causes severe kidney and liver inflammation, often presenting as acute kidney injury, jaundice, vomiting, and collapse. It is a zoonotic disease, meaning it can infect humans. The L4 vaccine covers four Leptospira serovars and is the standard of care in the UK. Annual vaccination with L4 is strongly recommended, particularly for dogs at elevated environmental risk.
Grape and Raisin Toxicity
Grapes, raisins, sultanas, and currants can cause unpredictable and potentially fatal acute kidney injury in dogs. What makes this toxicity unusual is that the toxic dose is entirely individual — some dogs consume large quantities without apparent harm, while others develop AKI after eating just a small amount. The toxic compound has not yet been definitively identified, which means no safe dose can be established.
Any ingestion of grapes or raisins by a dog should be treated as a veterinary emergency. Treatment involves inducing vomiting if the ingestion was recent, followed by intravenous fluid therapy and close monitoring of kidney function. Do not wait for symptoms to appear before seeking help.
Managing Chronic Kidney Disease
Once diagnosed with CKD, management focuses on slowing progression, controlling clinical signs, and maintaining quality of life. Key elements include:
- A prescription renal diet with reduced but high-quality protein, restricted phosphorus, and increased omega-3 fatty acids.
- Phosphate binders if dietary restriction alone does not control serum phosphorus levels.
- Maintaining good hydration — wet food or water fountains can encourage intake.
- Anti-nausea medication and appetite stimulants as needed.
- Blood pressure medication if hypertension is present.
- Anti-proteinuric treatment (typically an ACE inhibitor) if significant protein is being lost in the urine.
Regular monitoring — typically every one to three months depending on stage — allows your vet to detect deterioration early and adjust treatment accordingly.
When to Seek Urgent Help
Any dog showing sudden onset of vomiting, lethargy, reduced urination, or collapse — particularly following a possible toxic exposure — requires emergency veterinary assessment. Early treatment of AKI gives the kidneys the best chance of recovery. For dogs already diagnosed with CKD, an acute deterioration on top of chronic disease (termed acute-on-chronic) can occur and also warrants prompt veterinary review.
Understanding kidney disease in your dog, from the staging system your vet uses to the causes that trigger acute injury, puts you in a stronger position to respond quickly and advocate effectively for your pet's care.