Chronic Kidney Disease & IRIS Staging in Cats
Chronic kidney disease (CKD) is prevalent among cats and arises from persistent, irreversible alterations in kidney function that hinder their capacity to filter and eliminate toxins from the bloodstream.
This condition progresses gradually over weeks, months, or even years, with the rate of decline differing significantly among cats. Symptoms typically manifest when kidney function has diminished by approximately 75%. These signs are often non-specific and may encompass weight loss, increased thirst, increased urination, and diminished overall health.
WHAT CAUSES CHRONIC KIDNEY DISEASE?
Although most cases of CKD are idiopathic (have an unknown underlying cause), some causes are well recognised. These include:
- Polycystic kidney disease (PKD)
- Kidney tumours
- Infections
- Toxins and drugs
- Glomerulonephritis (an inflammatory condition)
- Trauma
- Stones affecting the kidneys and/or ureters
Kidney disease may also develop secondary to other diseases, such as heart disease, dental disease and high blood pressure.
If an underlying cause can be pinpointed, there are instances where it can be treated, potentially halting the progression of the condition. However, in most cases, treatment focuses on managing the disease and addressing any resulting complications.
SYMPTOMS OF CKD
In many instances, chronic kidney disease is a gradually worsening condition that develops slowly over time. Common symptoms observed in affected cats include:
- Increased thirst and/or urination
- Decreased appetite and weight loss
- Dull or unkempt coat
- Dehydration
- Constipation
- Lethargy or weakness
Additional symptoms may involve vomiting, halitosis, and oral ulcers
DIAGNOSIS
CKD is diagnosed using a combination of historical findings, physical examination, blood and urine tests, and/or abdominal ultrasound. Occasionally we screen for family or breed- elated kidney disorders (e.g. Polycystic kidney disease in Persian cats) allowing us to detect CKD in its very early stages, before symptoms are seen.
STAGING
Following diagnosis, the next step is to determine how advanced the disease is in order to instigate appropriate treatment and monitoring for each patient. This process is known as “Staging.”
The staging steps are as follows:
Fasting Blood Creatinine Concentration – Creatinine is a waste product of metabolism and is eliminated by the kidneys. If the patient is hydrated and creatinine increases, it indicates kidney function is reduced.
SDMA Test – SDMA is a sensitive “biomarker” of kidney function and can be readily assessed with a blood test. If the SDMA for your cat is elevated, we assess the result in combination with the creatinine result to accurately stage the CKD. The above two tests would likely have been performed for initial diagnosis, and they are repeated for the staging process when the patientis hydrated and stable so thatthe reading is a true representation of patient status in order to
make Staging more accurate and in line with the patients’ needs.
Urine Protein – A urine protein to creatinine ratio (UP/C) is used to both confirm and gauge the loss of kidney function. Simple dipsticks commonly used in practice can give false positives. Ideally two urine samples are collected over a 2 to 6 week period, then submitted to the lab for analysis. The higher the UPC ratio, the more advanced the stage of CKD.
Blood Pressure – The kidneys play an integral role in maintaining normal blood pressure. As function deteriorates, so does their ability to regulate blood pressure. Typically the blood pressure increases with a loss of function.
TREATMENT
The management of CKD depends on the stage (1-4) of the CKD, with specific treatments targeting individual abnormalities. Most cats respond well to dietary changes, supplements, and additional therapies. Your veterinarian will collaborate with you to determine the most suitable approach for your cat.
Special Diets
These diets restrict protein and lower phosphorus levels, reducing waste products in the blood. They can be obtained from your veterinary clinic.
Medical Management Option
Subcutaneous fluids (SC fluids): In advanced CKD stages, cats may struggle to stay hydrated by drinking. SC fluids are administered under the skin and can significantly improve quality of life.
B Vitamins: Cats with compromised kidney function may require supplementation of water-soluble vitamins like B12, to avoid signs of deficiency.
Blood pressure management: Many cats with CKD develop high blood pressure, which can further damage the kidneys and other organs such as the eyes.
Medications can help control high blood pressure.
Medication for protein in the urine: This condition accelerates CKD progression and requires specific treatment. Antibiotics: Cats with CKD are prone to frequent bladder infections, increasing the risk of kidney infections. Routine urine cultures are often recommended.
Potassium supplementation: Cats with renal failure often lose potassium in their urine, leading to muscle weakness, stiffness, and poor coat quality. Low potassium
levels can worsen kidney function.
Phosphate binders: Despite dietary adjustments, some cats may still have elevated blood phosphorus levels. Oral phosphate binders like aluminium hydroxide help decrease phosphorus absorption through the gut, improving your cat’s health and
slowing disease progression.
Symptomatic Management Options for Advanced Stages
Appetite stimulants: Appetite stimulants such as mirtazapine have been shown to improve appetite, reduce vomiting and increase weight gain in cats with CKD.
Anti-nausea medications: help to reduce nausea and vomiting and improve appetite.
Anaemia treatment: CKD can lead to anaemia due to reduced red blood cell production in the bone marrow. Medications to stimulate bone marrow function may be necessary.
Nutritional support: A feeding tube may be required for nutritional and hydration support and ease of medicating.
Although CKD is not a curable or reversible disease, appropriate support and treatment can both increase the quality of life and prolong life by slowing down the progression of the disease.