Chronic kidney disease (CKD) is a common disease in older animals. It affects 6% of cats and 1% of dogs, with the incidence
increasing to 15% in cats over 15 years old. Just as there are many different causes of chronic kidney disease, there are
many different levels of dysfunction.
IRIS staging system
The International Renal Interest Society has developed a staging system for kidney disease in dogs and cats, to facilitate
management recommendations and for standardization that will hopefully allow comparison in the research arena. Substages include
proteinuria and hypertension.
Stage I includes non-azotemic pets, such as a Persian cat with polycystic kidney disease. Clinical signs of uremia will not
be present; management involves monitoring the primary condition. Most pets with Stage II CKD are asymptomatic, with mild
elevations in BUN or creatinine, are maintaining body weight and appropriate hydration, and may not need specific treatment,
although routine monitoring is indicated. Pets with Stage III disease usually have some cIlinical signs, which may include
polyuria and polydipsia, or partial anorexia, among others. More intervention is usually needed for these animals. Most pets
with Stage IV CKD have significant clinical signs. Pets with CKD may develop a uremic crisis, characterized by acute decompensation
with dehydration and significant clinical signs, and they will need to be hospitalized for management. Once they are stabilized,
they can be sent home to continue outpatient management. About 30% of cats that present in a decompensated crisis can be stabilized
at 1 or 2 stages lower than presentation.
Nutrition: Stages II, III, IV
Use of a renal diet will double the survival time in dogs, compared to a maintenance diet, which makes it one of the most
potent treatments we have for CKD. Similar effects are seen in cats eating a renal diet. A renal diet is formulated to have
restricted protein and phosphorus. In addition to a restricted quantity of protein, the protein source should have high biologic
value, which generally means animal source protein. There are several commercial options available, including Hill's K//D;
Royal Canin Renal LP, Renal MP (dogs only), and Modified Formula; Purina CNM NF; Eukanuba Renal Disease Early Stage and Late
Stage diets for dogs (dry only) and Multi-Stage Renal Diet for cats. Several home-cooked recipes are available but have not
been rigorously evaluated.
If the pet is consuming exclusively a renal diet, the BUN:Creatinine ratio should be in the range of 10 to 15 (normal 15-20),
and alterations in this ratio can indicate gastrointestinal bleeding or poor patient or client compliance with dietary recommendations.
Enhancing dietary compliance
Pets with stage III or IV CKD may have anorexia that makes switching to a renal diet problematic. Because of the possibility
of creating a food aversion, a new diet should not be introduced in the hospital during a period of decompensation. Instead,
the new diet should be introduced once the animal is home and eating its normal diet. The new diet should be offered in a
separate bowl next to the regular food and removed after an hour and replaced at the next feeding time. After a few days,
offer the new food at times when the pet is hungriest, and then offer the regular food if the pet does not eat the new food.
Gradually decrease the amount of the regular food that is offered. It may take 3-4 weeks to completely switch a pet to the
renal diet. Weekly phone calls to the client may help encourage compliance.