The suit concerns prescription pet foods that cost more, but that plaintiffs contend are no different than any other kind of pet food. Some highlights in this complaint:

Dear Dr. Fox: I have a 13-year-old beagle-shepherd-Lab mix named Nibbles. At her last vet appointment, her tests showed kidney problems.

Up until that point, she had always been eating Nutro Max dog food, and was on the senior formula. The vet, who I’ve gone to for years and do trust, put her on new food, Hills Prescription Diet k/D Kidney Support, which has “less phosphorus, protein and salt” — or so he said. Looking at this food’s ingredients and comparing them with Nutro Max, it seems to me like this new food has a lot more junk ingredients in it, and more fat.

Now, if this diet works despite all the crap ingredients, then fine! The issue is, prior to the diagnosis, I had seen no sign of kidney issues. Now, after about a month on this food, she seems very antsy and anxious; she pees more than she used to, drinks more than she used to and seems hungrier. The main reason I am writing is that last night, she wet the bed (she released her whole bladder). This has never happened before!

The reason she went to the vet in the first place was merely for a senior exam, during which I mentioned her recently insatiable appetite, and her weight loss (she’s lost about 5 pounds). Her whole life, she’s received a half-cup of food in the morning and a half-cup at night. We upped it to an extra half-cup in the past year, and now with the new kidney support diet, we upped it to 2 full cups a day.

Is this recent bed-wetting and altered behavior part of the kidney cleansing process? Or is this making her issue worse? To me, it seems like the less I feed her, the better (for example, go back to only 1 cup of food per day), but she is so hungry, and that also seems kind of mean. She also takes a kidney-support vitamin (VetriSCIENCE). — H.P., Washington, D.C.

Dear H.P.: Dogs with chronic kidney disease, when accurately diagnosed, need careful monitoring of blood pressure, dietary phosphate, potassium and blood urea nitrogen, as per my article on kidney disease posted on my website, www.DrFoxVet.net.

The ingredients in the special prescription diet are of dubious value, possibly harmful and certainly not providing your dog with sufficient nutrients if she is constantly hungry.

This is no way to go. Chronic kidney disease can lead to sarcopenia — wasting of muscles due to the kidneys passing out more protein. So your dog needs some good-quality protein in her daily diet.

Dogs with kidney disease drink more, so take your dog out more frequently to urinate. But this, coupled with the increased appetite, could be related to di-abetes, which I would have your dog checked for, along with a blood test to see how her kidneys are functioning.

Do keep me posted on the outcome, and good luck.