A 13 yo cat with CKD stage 2, hypertensive, non-proteinur...

Yes, absolutely. IRIS Stage 2 is the ideal time to transition to a therapeutic renal diet. This is one of the most effective interventions we have to slow the progression of CKD.

My primary goal at this stage is phosphorus restriction. The evidence is very clear that limiting dietary phosphorus can slow the decline in GFR and improve survival time. We should aim to maintain serum phosphorus below 5.0 mg/dL. A commercial therapeutic renal diet is the most effective way to achieve this.

While these diets also feature moderate protein restriction, it's the phosphorus control that is most critical in early-stage disease. For a cat, we must be careful to avoid excessive protein restriction that could lead to sarcopenia. The protein in renal diets is highly bioavailable to meet their needs while reducing nitrogenous waste.

Other key benefits of making the switch now include:
* Omega-3 Fatty Acids: Most renal diets are supplemented with EPA/DHA, which have renoprotective anti-inflammatory effects.
* Potassium Supplementation: They are typically fortified with potassium to help combat the hypokalemia common in feline CKD.
* Sodium Restriction: This is particularly important for your patient given the concurrent hypertension.

My recommendation is to begin a slow transition over 7-14 days, mixing the new diet into the old one. Palatability is paramount; food aversion is a major risk in these cats. I suggest trying several different brands and formulations (pâté, morsels, dry) to find one she will reliably eat.

After the transition, we should recheck weight, BCS, MCS, and a chemistry panel in 4-6 weeks to ensure adequate caloric intake and to verify our phosphorus control.

This is a key inflection point in managing her disease, and a successful diet change now can make a significant difference long-term.

— Dr. Yuki Tanaka 🥗

This is an excellent and very common question. The IRIS guidelines recommend introducing a renal diet in Stage 2, so your timing is appropriate. My approach here is driven by two main priorities: managing phosphorus and maintaining caloric intake.

The primary benefit of a therapeutic renal diet at this stage is phosphorus restriction, which is key to slowing the progression of renal secondary hyperparathyroidism. These diets are also typically sodium-restricted (beneficial for the hypertension) and contain buffered potassium and supplemented omega-3 fatty acids.

However, my main concern in any feline CKD patient is food aversion and subsequent weight loss. Inappetence is the enemy.

Here is my recommended approach:

Check Serum Phosphorus: Before making any changes, confirm the patient's current phosphorus level. The IRIS target for Stage 2 is <4.6 mg/dL. If the level is already approaching this target on their current diet, the impetus to switch is higher. If it's well below (e.g., <3.5 mg/dL), you have more flexibility.

Prioritize a Slow Transition: Do not make an abrupt switch. The goal is to transition over several weeks to maximize acceptance. If at any point the cat reduces their total food intake, I would pause or slow the transition. It is far better for a cat to eat a non-renal diet than to eat an insufficient amount of a renal diet.

Have a Backup Plan: If the cat absolutely refuses multiple formulations of therapeutic renal diets (canned, dry, different brands), my next step is not to force the issue. Instead, I would keep them on the most palatable senior or adult maintenance diet they will reliably eat and add a phosphorus binder (e.g., aluminum hydroxide) to the food. This isn't perfect, but it achieves the most critical goal of phosphorus control while maintaining body condition.

Yuki will have some excellent specific diet recommendations and transition strategies, but from a medical standpoint, this is a situation where perfect can be the enemy of good. Maintaining appetite and muscle mass is paramount.

Recommendation Confidence: High confidence.