At its core, CKD signifies a long-term process of kidney damage that results in your pet's kidneys' diminished ability to perform their vital functions. Your pet's kidneys play a pivotal role in whole body homeostasis. Their functions include the selective elimination of metabolic waste products and, more importantly, the homeostatic regulation of water and ion content in the body through the filtration of blood and excretion of urine.

This process, known as glomerular filtration, occurs in Bowman's space, where urine is formed, excluding cells and most protein-bound compounds, although a small amount of albumin is filtered. The filtrate then undergoes bulk reabsorption in the proximal tubule, with further secretion or reabsorption of various compounds. The loop of Henle is responsible for concentrating and diluting the filtrate by selectively reabsorbing water and sodium. Finally, the distal convoluted tubule and collecting ducts fine-tune the urine's solute and moisture content.

Beyond these filtration and reabsorption processes, your pet's kidneys are deeply involved in other critical functions. They play a crucial role in the metabolic regulation of acid-base status. Additionally, the kidneys have endocrine functions, producing essential hormones such as erythropoietin, which stimulates red blood cell production , and playing a role in vitamin D activation.

Furthermore, the kidneys are involved in blood pressure regulation through the production of renin and the adrenal secretion of aldosterone. Therefore, when renal function declines in CKD, these normal processes are disrupted, leading to the retention of substances that should be excreted (such as phosphorous and creatinine) and the loss of compounds that should be retained (such as water and protein).

The retention or loss of various compounds due to impaired kidney function leads to the observable clinical signs of CKD in your pet. Many, though not all, patients exhibit signs of chronic illness, including loss of body condition, body weight loss, muscle mass loss, and an unkempt appearance. Due to your pet's kidneys' inability to regulate water balance, polyuria (increased urination) and polydipsia (increased thirst) are common signs you may notice at home.

Other potential signs include hyporexia (reduced appetite) or anorexia (complete loss of appetite), vomiting, halitosis (bad breath), and ulcerative stomatitis and gastroenteritis. On physical examination, your pet's kidneys may often feel small and irregular, a finding that can be confirmed through abdominal radiography and ultrasonography. Occasionally, kidney enlargement (renomegaly) may be present in CKD cases complicated by renal neoplasia (cancer), pyelonephritis (kidney infection), or ureteral obstruction.

Biochemically, several abnormalities are typically observed in animals with CKD. Azotemia, characterized by elevated levels of urea and creatinine in the blood , is common and is often accompanied by inappropriately dilute urine, with a urine specific gravity (USG) less than 1.030 in dogs and less than 1.035 in cats. Metabolic acidosis and hyperphosphatemia (elevated phosphate levels) are also frequently present in your pet's bloodwork.

Some patients, particularly cats, may develop hypokalemia (low potassium levels). Nonregenerative anemia (a decrease in red blood cell production), hypoalbuminemia (low albumin levels), and dyslipidemia (abnormal lipid levels) can also occur, and there may be an increased susceptibility to bacterial urinary tract infections. Systemic arterial hypertension (high blood pressure) is a significant concern, affecting 40% to 75% of patients with CKD . Proteinuria (the presence of excessive protein in the urine) may also occur and has been associated with a poorer prognosis and faster progression of CKD in your pet.

The International Renal Interest Society (IRIS) has developed a staging system for CKD based on serum creatinine concentrations . A serum creatinine greater than 1.6 mg/dL in cats and greater than 1.4 mg/dL in dogs is generally considered azotemic. However, significant renal disease can be present in your pet even without azotemia (IRIS stage 1).

Therefore, when measuring your pet's serum creatinine, a urine specific gravity should always be determined concurrently to aid in interpretation. A complete urinalysis provides valuable information about your pet's urinary tract health and should be part of the minimum diagnostic database. The IRIS staging system, which also incorporates proteinuria and blood pressure, is crucial for guiding your pet's therapy, monitoring their condition, and allowing for comparison of your pet's disease with others.

The primary objectives of CKD treatment are to minimize the clinical signs of uremia, slow the progressive loss of renal function, and preserve your pet's nutritional status . Establishing an appropriate treatment plan for your pet involves several key areas, including controlling electrolyte imbalances, managing vomiting and inappetence, providing hormone replacement, and controlling hypertension and proteinuria.

Dietary management is a fundamental aspect of CKD treatment in both human and veterinary medicine, with renal diets providing the greatest benefit supported by extensive evidence. Restricting your pet's dietary protein can help decrease the amount of organic acids that the kidneys need to excrete, potentially easing the burden on their compromised kidneys. Phosphorus restriction is also crucial in managing your pet's CKD.

Ensuring adequate hydration is vital for patients with impaired urine concentrating ability, and feeding your pet wet food can help increase their water intake . While commercial renal diets are strongly recommended for azotemic cats (IRIS stages 2-4), home-prepared diets may be an alternative if properly balanced by a veterinary nutritionist to meet your pet's desired nutrient requirements with reduced protein and phosphorus levels.

This is common in CKD due to the retention of acids in your pet's system. Bicarbonate therapy, often using potassium citrate (75 mg/kg orally every 12 hours initially), is preferred as it provides both alkalization and potassium supplementation for your pet. Sodium bicarbonate (8-12 mg/kg orally every 8-12 hours) can also be used but may worsen hypertension and fluid retention due to its sodium content.

Anemia in CKD can be managed by pharmacologically stimulating your pet's red blood cell production. Erythropoietin and darbepoetin are used to stimulate red blood cell production . However, a significant limitation of erythropoietin is the potential development of antierythropoietin antibodies in 20% to 70% of patients.

Iron supplementation, such as ferrous sulfate (dogs: 100-300 mg orally daily; cats: 50-100 mg orally daily), is often necessary to address iron deficiency due to blood loss in your pet. The goal hematocrit is often around 35% to 40%.

Hyperphosphatemia and Renal Secondary Hyperparathyroidism: Phosphate binders can help control elevated phosphorus levels in your pet's bloodstream. Calcitriol supplementation (initial dose of 2.0-2.5 ng/kg orally every 24 hours) may help decrease serum phosphorus and parathyroid hormone concentrations. It should be administered to your pet in the evening on an empty stomach to reduce the risk of hypercalcemia.

Calcitriol has been shown to improve survival in dogs with stage 3 or 4 CKD but has not been proven beneficial in cats with any stage of CKD.

For nutritional supplementation, omega-3 fatty acids may support kidney function, especially in dogs, and some evidence suggests a survival benefit in cats fed diets higher in them. B vitamins are often included in renal diets to replace those lost through increased urination. Potassium supplementation, frequently with potassium citrate or gluconate in cats, helps manage hypokalemia and potassium citrate can also aid in alkalization.

Maintaining your pet's lean muscle mass and optimal body condition (Body Condition Score [BCS] of 2.5 to 3 out of 5 or 4 to 5 out of 9, and Muscle Condition Score [MCS]) is crucial for their overall health. Appetite stimulants like mirtazapine or cyproheptadine may be used if needed to encourage your pet to eat.

Due to the progressive nature of CKD, regular monitoring of your pet is essential . This includes periodic check-ups at the veterinary clinic, ideally every 1-2 months. As your pet's caregiver, you play a key role in monitoring for any changes in clinical signs such as anorexia, vomiting, lethargy, changes in water intake and urination, and weight loss.

Regular bloodwork, including serum creatinine, BUN, phosphorus, potassium, and bicarbonate levels, as well as urinalysis and blood pressure measurements, are important to assess your pet's disease progression and response to treatment.

It is important for you to understand that CKD is typically a progressive and often uncurable condition in your pet. The severity of proteinuria has been linked to survival in cats with naturally occurring CKD. However, with appropriate management, many dogs and cats with CKD can maintain a good quality of life for months to years .

The focus of your pet's treatment is not only on prolonging their life but also on ensuring they remain comfortable and maintain a good quality of life. Effective communication between your veterinary team and you is vital for successful management, ensuring you are well-informed and actively involved in your pet's care.

Chronic Kidney Disease is a significant health concern for our aging dog and cat population. Early detection of CKD in your pet , followed by a comprehensive management plan involving dietary modifications, appropriate medical therapies, and consistent monitoring, is crucial for slowing disease progression and maintaining a good quality of life for your beloved companion.

By being vigilant for early signs and working closely with your veterinarian , you can help your pet with CKD live a more comfortable and fulfilling life. Remember that individualized treatment plans are essential for your pet, and regular communication with your veterinary team will ensure the best possible outcome for your furry friend.