What Is Chronic Kidney Disease in Dogs?
Chronic kidney disease (CKD) — sometimes referred to as chronic renal failure or chronic renal insufficiency — is a progressive, irreversible condition in which the kidneys gradually lose their ability to filter waste products, regulate fluid balance, control blood pressure, and produce hormones including erythropoietin. Because the kidneys have considerable functional reserve, clinical signs typically only become apparent once more than 75% of the functional renal mass has been lost.
CKD is most commonly diagnosed in older dogs, though some breeds — including Cocker Spaniels, German Shepherds, Bull Terriers, and Shih Tzus — have hereditary forms that can present at a younger age. The causes are diverse and include glomerulonephritis, renal dysplasia, pyelonephritis, leptospirosis sequelae, hypercalcaemia, and long-term use of nephrotoxic drugs. In many cases, no underlying cause is identified.
Recognising the Signs of CKD
Because CKD is a slowly progressive disease, clinical signs often develop gradually and may initially be attributed to normal ageing. Owners who are attuned to their dog's normal behaviour are best placed to detect subtle changes early.
- Increased thirst and more frequent urination — often the earliest and most noticeable signs
- Reduced appetite and gradual weight loss
- Lethargy and reduced enthusiasm for exercise or play
- Vomiting and nausea, particularly in the morning
- Bad breath with an ammonia-like or "uraemic" smell
- Mouth ulcers in advanced disease
- Pale gums due to anaemia of chronic disease
- High blood pressure, which can cause sudden blindness due to retinal detachment
Any dog over seven years of age should have kidney function assessed annually as part of a senior wellness screen, even in the absence of symptoms. Early-stage CKD identified on routine bloods carries a significantly better prognosis than disease discovered at an advanced clinical stage.
IRIS Staging: How CKD Is Classified
The International Renal Interest Society (IRIS) has developed a widely adopted staging system for CKD in dogs and cats that is used globally to guide treatment and monitoring decisions. It is based primarily on fasting plasma creatinine concentration — measured on at least two occasions when the dog is stable and well hydrated — and is further substaged according to urine protein:creatinine ratio (UPC) and systemic blood pressure.
- IRIS Stage 1: Creatinine below 125 micromol/L. Non-azotaemic — no measurable waste product accumulation. May be identified by other markers such as SDMA or abnormal urinalysis. Subtle functional changes present.
- IRIS Stage 2: Creatinine 125–250 micromol/L. Mild azotaemia. Dogs are often still clinically well but benefit from dietary adjustment and regular monitoring.
- IRIS Stage 3: Creatinine 251–440 micromol/L. Moderate azotaemia. Clinical signs become more apparent. Active management including dietary intervention, phosphate control, and treatment of hypertension is essential.
- IRIS Stage 4: Creatinine above 440 micromol/L. Severe azotaemia. Dogs at this stage require intensive supportive care, and quality-of-life considerations become increasingly central to clinical decisions.
IRIS and WSAVA guidelines both recommend that SDMA (symmetric dimethylarginine) — a biomarker that rises earlier than creatinine — be included in routine senior screening panels, as it may allow CKD to be identified at Stage 1 before azotaemia is established.
The Critical Role of Diet in CKD
Nutritional modification is the single most important non-pharmacological intervention in CKD management. The goals of dietary therapy are to reduce the accumulation of uraemic toxins, restrict phosphate intake (which is central to slowing disease progression), maintain lean body mass, and support overall quality of life.
Phosphate Restriction
Phosphate retention is one of the most damaging consequences of failing kidneys, leading to renal secondary hyperparathyroidism, mineral dysregulation, and accelerated nephron destruction. Reducing dietary phosphate is recommended from IRIS Stage 2 onwards, and becomes increasingly urgent as the disease advances. Prescription renal diets are formulated with significantly reduced phosphate content compared to standard maintenance diets. WSAVA nutritional guidelines strongly recommend their introduction as early as Stage 2, as evidence supports a slowing of disease progression when phosphate restriction is achieved.
Protein Levels
Dietary protein in CKD management is a nuanced area. Excessive protein increases the production of nitrogenous waste products that the damaged kidneys struggle to excrete, contributing to uraemic signs. Renal diets provide moderate, high-quality protein to meet maintenance requirements without generating excess waste, while avoiding the muscle wasting that can occur with severe protein restriction.
Prescription Renal Diets
Several evidence-based prescription renal diets are available for dogs with CKD. Both Hill's Prescription Diet k/d — Kidney Care and Royal Canin Veterinary Diet Renal are well-established choices with clinical data supporting their use in slowing CKD progression.
Hill's k/d provides controlled protein and phosphate alongside omega-3 fatty acids (EPA and DHA), which have anti-inflammatory effects on the renal vasculature. Royal Canin Renal is formulated with low phosphate, moderate protein, and includes a combination of antioxidants to reduce oxidative stress within renal tissue. Both diets are available through Zooplus, which offers a convenient subscription option for owners who need to maintain a consistent and uninterrupted supply — particularly important given that dietary consistency is essential for monitoring the dog's response to treatment.
Phosphate Binders
In some dogs — particularly those at IRIS Stage 3 and 4 — dietary phosphate restriction alone is insufficient to achieve target serum phosphate concentrations. In these cases, oral phosphate binders are prescribed. Aluminium hydroxide, calcium carbonate, and lanthanum carbonate-based products can be mixed with food to reduce intestinal phosphate absorption. They are generally well tolerated and represent an important additional tool when diet alone does not achieve the IRIS-recommended phosphate targets.
Medications Used in CKD Management
Systemic hypertension is extremely common in dogs with CKD and, if left untreated, accelerates glomerular damage and increases the risk of neurological and ophthalmic complications. Regular blood pressure monitoring is an essential component of CKD care.
Semintra (Telmisartan) is an angiotensin receptor blocker (ARB) that is EU-licensed for the management of CKD-associated proteinuria in cats, where it has demonstrated significant reduction in protein loss. While not currently licensed specifically for dogs, telmisartan is used off-label in canine CKD patients — particularly those with significant proteinuria — based on its mechanism of action and the growing body of clinical experience in dogs. Its use in dogs should always be under direct veterinary supervision with appropriate monitoring of renal parameters and blood pressure.
Benazepril (an ACE inhibitor) is another commonly used antihypertensive and anti-proteinuric agent in dogs with CKD, and is often the first-line choice given its established evidence base in this species.
Hydration and Quality of Life
Dogs with CKD are prone to dehydration because the damaged kidneys are unable to concentrate urine efficiently. Ensuring adequate water intake is vital. Switching to a wet or mixed diet, providing multiple fresh water sources, and using pet water fountains can all encourage dogs to drink more. In advanced stages, some owners are taught to administer subcutaneous fluids at home, a technique that significantly improves quality of life and allows more frequent fluid support between veterinary visits.
With early detection through annual senior screening, appropriate dietary management using renal diets from sources such as Zooplus, blood pressure control, and phosphate management, many dogs with CKD can be maintained in excellent quality of life for months to years following diagnosis.