higher fiber but also higher protein food for old cat

[Mareva]

Hi,
My 14-year-old cat had recently a constipation episode. The vet suggested to change her food from 1st Choice for senior cats to Hills's Prescription diet w/d. Although this food has lower fat and minerals and more fibers, it also has more protein (min. 34%) than my current food (min. 30%). My cat being an Himalayan, they have a tendency to have kidney problem. So far my cat doesn't have symptoms of kidney problems, but I was wondering in giving it food with a bit more protein would be such a good idea? Should I ask my vet for a food with high fiber and lower protein than 34%, or is the 4% difference not relevant? I'd like an second opinion,
Thank you!
Maria