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Table of Contents
Types of kidney disease in cats
The kidneys are vital organs and have a critical role in urine production, filtration and excretion of toxins, maintaining fluid balance, hydration, blood pressure, pH, balance of calcium and phosphorus, and red blood cell production. Like us, cats have two kidneys, distinctive bean-shaped organs that are located on either side of the spine. Each kidney contains around a million microscopic filtering units called nephrons. As filtrate travels through these units, essential substances like water, glucose, and electrolytes are reabsorbed into the bloodstream, while waste products and excess substances are concentrated into urine. The urine is then carried through the ureters to the bladder for storage and eventual elimination through the urethra. We are born with many more nephrons than we need – over time or due to a certain disease process, nephrons are damaged and die off. When only ⅓ of nephrons are left, a patient may present with signs and indicators of kidney disease. There are two types of kidney disease that can develop in cats.Chronic kidney disease (CKD)
CKD involves the gradual and irreversible loss of functional kidney units (nephrons). Signs of kidney disease may not be evident until ⅔ of the nephrons have been damaged. While there is no treatment for CKD, early detection and treatments can help slow the progression of the disease. CKD is extremely common in senior cats, affecting an estimated 30-40% of cats over 10 years and 81% of cats over 15 years. There are several possible causes:- Age-related degeneration
- Congenital abnormalities – inherited issues such as polycystic kidney disease, amyloidosis, or renal dysplasia. These occur more commonly in certain breeds.
- Infections – such as pyelonephritis (kidney infection), feline infectious peritonitis, feline leukemia virus, feline immunodeficiency virus, or tick-borne disease
- Glomerulonephritis – inflammation of the filtering units
- Neoplasia – cancers, such as lymphoma
- Kidney or ureteral stones
- Secondary to acute kidney injury
- Idiopathic (unknown cause)
Acute kidney injury (AKI)
AKI is characterized by a rapid and severe decline in kidney function, often triggered by a toxin, infection, or urinary obstruction. With prompt and appropriate treatment, recovery of kidney function may be possible. Triggers of acute kidney injury in cats include:- Toxins – such as ingestion of lilies, antifreeze, rodenticide, or certain medications like NSAIDs
- Infections – such as pyelonephritis
- Urinary obstruction – inability to urinate
- Organ failure
- Ischemia, shock, trauma, or low blood pressure
Symptoms of kidney disease
It’s important for pet parents to be aware of the signs of feline kidney disease, including:- Increased thirst (polydipsia) – Most owners rarely see their cats drink water, especially if they eat a canned food diet, so this can be a big clue that something is amiss. Cats with kidney disease drink more water because they are trying to keep up with fluid loss through large amounts of dilute urine. They also need more water in an attempt to help flush out toxins.
- Increased urination (polyuria)
- Lethargy
- Poor appetite
- Weight loss
- Vomiting
- Urinary accidents, incontinence, or inability to urinate
- Bloody urine (hematuria)
- Ulcerations in the mouth and bad breath
- Vision disturbances as a result of high blood pressure
How veterinarians diagnose kidney disease
In addition to a medical history and thorough physical exam, kidney disease is diagnosed on routine bloodwork and urine testing.Bloodwork
Bloodwork provides insights into kidney function by measuring creatinine and BUN (blood urea nitrogen). These waste products increase in the blood when kidney function declines. They are also responsible for making your pet feel ill. Electrolyte imbalances (potassium, phosphorus, calcium) are also common in kidney disease. It’s important to examine the numbers of red and white blood cells, as anemia (decreased red blood cells) is common in cats with CKD, while high numbers of white blood cells may indicate infection or inflammation. SDMA (symmetric dimethylarginine) is a newer and more sensitive biomarker that can detect kidney dysfunction earlier than traditional bloodwork values. Ask your vet if this test is recommended for your cat.Urinalysis
An evaluation of the urine is essential for assessing kidney health. Cats with kidney disease often produce dilute urine (low urine specific gravity). Proteinuria (protein in the urine) is another indicator of kidney damage.Additional diagnostics
Additional tests may be recommended to help determine the extent of kidney damage and look for an underlying cause.- Blood pressure measurement is important because hypertension is a common complication of kidney disease.
- Imaging can also provide valuable information. Radiographs (X-rays) help assess kidney size and shape, and can potentially reveal stones or other abnormalities. Ultrasound provides a detailed evaluation of the kidney’s internal structure and architecture.
- A urine culture can help detect and grow bacteria causing an infection.
- Urine protein creatinine ratio (UPCR) can help determine the significance of protein in the urine.
- In certain cases, a renal biopsy might be recommended to obtain a tissue sample and definitively diagnose the underlying cause of the kidney disease.
Staging of kidney disease
If your cat has been diagnosed with chronic kidney disease, your vet will determine their stage of disease, based on guidelines from the International Renal Interest Society (IRIS) considering creatinine levels. Here’s a very simplified summary of the IRIS CKD Stages:- Stage 1: Early kidney disease. Creatinine may be within the normal range or slightly elevated and clinical signs are usually not apparent.
- Stage 2: Mild kidney disease. Creatinine levels are moderately elevated.
- Stage 3: Moderate kidney disease. Creatinine levels are significantly elevated.
- Stage 4: Severe kidney disease. Creatinine levels are very high, and the cat is likely to be showing clinical signs of severe disease.
Treatment of kidney disease in cats
In general, there is no cure for CKD, so the goal of treatment is to slow the progression of the disease, manage symptoms (such as vomiting and loss of appetite), and control complications (such as anemia and high blood pressure). This often involves a combination of diet, fluid support, and medication. In some cases (especially those of acute kidney injury), an underlying cause may be identified and treated – examples would be treating a kidney infection with antibiotics or unblocking a cat with a urinary obstruction. Cats who are severely ill often require hospitalization for several days for IV fluids or even hemodialysis if available. Your veterinarian will tailor a specific treatment plan for your cat based on the stage of kidney disease, individual needs, and response to therapies. Regular checkups and monitoring are essential for optimal management and adjustment of the treatment plan over time. Let’s explore some of the common treatment options for cats with CKD:- Prescription renal diets: Specially formulated renal diets contain restricted protein and phosphorus to reduce the workload on the kidneys. These diets can be prepared at home with careful guidance or purchased as ready-made prescription formulas from your veterinarian. Your veterinarian will recommend the most appropriate diet (like Hill’s Prescription Diet K/D, Purina Veterinary Diet NF, or Royal Canin Renal Support) based on your cat’s needs.
- Phosphate binders: If dietary phosphorus restriction alone is insufficient, phosphate binders are medications that reduce the absorption of phosphorus from the intestines, helping to maintain healthy blood phosphorus levels.
- Antibiotics: Cats with kidney disease are more susceptible to urinary tract infections, which can further worsen kidney function. Regular urine cultures and antibiotics, when necessary, are important.
- Potassium supplementation: Kidney dysfunction can lead to excessive potassium loss through the urine. Supplementation helps maintain normal potassium levels, which is essential for muscle function and overall well-being.
- B Vitamins: These water-soluble vitamins can become depleted in cats with kidney disease. Supplementation may be necessary to support overall health.
- Anti-emetics: Nausea and vomiting are common in cats with kidney disease. Anti-nausea medications can help control these symptoms, improving appetite and quality of life.
- Blood pressure management: Hypertension (high blood pressure) is often seen in cats with kidney disease, and requires treatment to prevent associated complications. Medications are used to lower blood pressure to a safe range.
- Management of proteinuria: Reducing protein loss through the urine (proteinuria) can help slow the progression of CKD. Special medications might be recommended for this purpose.
- Treatment of anemia: Kidneys play a role in red blood cell production. Anemia is a common complication of CKD, and treatments may include medications to stimulate red blood cell production.
- Subcutaneous (SQ) fluids: Providing additional fluids under the skin can be beneficial for cats with kidney disease, especially in later stages when they may struggle to maintain adequate hydration through drinking alone. Your vet team can teach you how to do this at home.
Prognosis and prevention
Kidney disease is a complex and often progressive condition in cats. While there is no cure for CKD, early diagnosis, proactive treatment, and ongoing veterinary care can significantly slow disease progression and improve your cat’s quality of life for months to years. In cases of acute kidney injury, the potential for recovery depends on the underlying cause, severity of damage, and how quickly treatment is initiated. Many causes of AKI, such as ingestion of antifreeze or lilies, are often fatal. However, cats who survive the initial incident with appropriate treatment often go on to do well long-term. Preventive strategies like regular veterinary checkups (especially for senior cats), providing ample fresh water, and avoiding potential toxins can play a crucial role in protecting your feline companion’s kidney health.FAQ
In most cases, kidney disease itself is not directly painful. However, symptoms such as vomiting, nausea, and ulcers in the mouth, can be extremely uncomfortable and debilitating, especially in end stage disease.
While kidney disease is often diagnosed based on bloodwork and urinalysis, your vet will likely recommend additional tests to help stage the disease and determine if there may be a treatable underlying condition. This may include blood pressure measurement, urine culture, and imaging.
The lifespan of a cat with kidney disease depends on the type of disease (acute vs. chronic), the stage at diagnosis, the underlying cause, and how well the cat responds to treatment. Early diagnosis and appropriate management are key to maximizing both survival time and quality of life. While there’s no single answer, with optimal care, many cats live comfortably for months or even years after a kidney disease diagnosis.
