Webinar Club- CKD in Cats, \"What's new in an old disease\"

Redefining Feline CKD: Moving Beyond the "Umbrella" Diagnosis

Chronic Kidney Disease (CKD)

In cats is often treated as a single disease entity, but in reality, it is a heterogeneous umbrella diagnosis.

It represents a persistent reduction in kidney structure or function caused by various conditions with different etiologies, management needs, and prognoses.

While we often assume chronic tubulointerstitial nephritis is the culprit (especially when no other cause is found), the biological behavior of the disease varies greatly between individuals.

The Evolution of IRIS Guidelines

The International Renal Interest Society (IRIS) guidelines remain the "gold standard" cheat sheet for clinicians. However, the latest updates emphasize a shift toward cat-specific nuances that the general pocket guides may overlook:

• Proteinuria (UPC): While a UPC >0.4 is a landmark for CKD, values between 0.2 and 0.4 (borderline) are now recognized as clinically significant in cats.

• SDMA and Creatinine: Treatment for hypertension can cause a slight increase in these values. This doesn’t necessarily mean the kidneys have worsened; it is often an expected finding of the medication.

• FGF23 vs. Phosphate: There is a shift toward using FGF23 as an early biomarker to determine when to restrict phosphate, helping to prevent mineral bone disorders before phosphate levels even rise.

Common Pitfalls in Diagnosis and Staging

1. The Danger of Premature Diagnosis

Before labeling a cat with a progressive, incurable disease, clinicians must confirm the condition is truly chronic and not a reversible Acute Kidney Injury (AKI).

• Ensure results are repeatable.

• Rule out "lab glitches," pre-renal causes, or infections (like pyelonephritis).

• Tip: If a Stage 1 or 2 cat presents with vomiting or sudden weight loss, look for concurrent conditions. Early-stage CKD rarely causes these symptoms; chronic enteropathy is a much more likely culprit.

2. Muscle Condition Score (MCS)

MCS is highly underreported but critical. Muscle loss directly impacts creatinine levels. For example, breeds like the Birman have naturally higher creatinine baselines. Without a baseline and an MCS, a single lab result can be easily misinterpeted.

3. Lab Variability

Recent studies show that the same blood sample run at four different labs can result in different IRIS staging. One in five cats may be mis-staged simply due to lab calibration differences.

Clinical Pearl: Always use the same reference lab for monitoring to ensure trends are accurate. Individual trends are far more reliable than fixed cut-off values.

Emerging Therapies and Management Strategies

Managing Uremic Toxins (Porus One)

Uremic toxins, like indoxyl sulfate, result from protein metabolism in the colon. When kidneys fail, these toxins build up, causing further renal damage and systemic inflammation.

• Porus One (Renaltec): These tiny spheres bind toxins in the gut, which are then excreted in feces.

• Unlike traditional binders, they do not interfere with amino acid absorption and are well-tolerated when mixed with food.

The "Cat-Specific" Protein Dilemma

In humans and dogs, reducing protein intake helps control uremic toxins. In cats—obligate carnivores—dropping protein too low leads to muscle wasting, the number one negative prognostic factor.

• The Goal: It’s not about "low protein" as a blanket rule; it’s about high-quality, highly digestible protein and maintaining caloric intake to preserve lean body mass.

Addressing Anemia (Molyidustat)

Anemia in CKD is linked to reduced quality of life and survival. Traditional EPO-stimulating agents carry risks of hypertension and antibody development.

• Molyidustat (Varenzin-CA1): A new oral HIF-PH inhibitor that "tricks" the body into producing its own erythropoietin.

• Dosing: Once daily for 28 days, followed by a break. It is highly effective and more practical for owners than weekly injections.

The "Japanese Vaccine" (AIM Protein)

Current research is exploring the AIM (Apoptosis Inhibitor of Macrophages) protein. In CKD cats, this protein is often "trapped" and unable to clear inflammatory debris in the kidneys.

• Preliminary studies show that injecting a modified AIM protein can slow the rise of creatinine and significantly increase one-year survival rates.

Conclusion: Focus on the Cat, Not the Paper

The most important takeaway for modern CKD management is to treat the patient, not the numbers. A four-point shift in creatinine that moves a cat from Stage 2 to Stage 3 on paper may just be biological variation.

Prioritize:

1. Hydration and appetite.

2. Managing concurrent enteropathy or hypertension.

3. Maintaining muscle mass.

4. Preserving the human-animal bond by minimizing the stress of medication.