One of the functions of the kidneys is to eliminate excess stomach acid. When the kidneys are impaired, they are less able to perform this function and acidosis is often the result. Excess stomach acid often leads to loss of appetite and in severe cases vomiting bile (foam). An acid reducer is needed too keep your renal patient's stomach in balance such as Famotidine(Pepcid), Ranitidine(Zantac), or Omeprazole (Prilosec). Most veterinarians recommend Famotidine(Pepcid). While Famotidine can be an excellent treatment, it has the unfortunate side-effect of causing nausea. If your pet is not getting relief from Famotidine please consult with your vet about whether Zantac or Omeprazole may be option.