Many puppies with renal dysplasia or kidney disease have elevated phosphorus (phosphate) levels (hyperphosphatemia). Normal range in dogs is 2.5 mg/dL to 6 mg/dL (0.8–1.9 mmol/L). It is important to note that growing puppies in general have higher levels of phosphorus in their bodies due to growth hormone and bone development. Elevated phosphorus levels in puppies by itself without other bloodwork or urinalysis abnormalities may not be a health concern. While phosphorus is an essential mineral for dogs to maintain healthy bones, and does not by itself cause kidney disease, dogs with kidney disease have issues getting rid of the phosphorus, which lead to a build up in their blood/bodies. Studies have shown that limiting dietary phosphorus can help prolong life and slow kidney disease progression.
There is a delicate balance between phosphorus and calcium levels in the body. Dogs with elevated phosphorus levels may also have low levels of calcium (hypocalcemia). In an attempt to balance the phosphorus, the body may leach calcium from the bones, and form calcium phosphate deposits in the body which is damaging. Hypocalcemia also has other symptoms and can lead to other health issues.
In addition to putting puppies on a kidney-support diet which has lower phosphorus, vets often recommend owners to add phosphorus binders to their food to further reduce phosphorus absorption. All things equal, I prefer to restrict phosphorus amounts in the diet first, rather than using binders.
Restricting Phosphorus in diet
Phosphorus is an essential mineral for dogs, especially growing puppies. It is important to balance this need whilst also supporting the kidneys. In general, restricting protein will lead to a lower phosphorus diet, and many commercial kidney diets go this route. I personally prefer to focus on restricting phosphorus itself rather than protein. Studies have shown that restricting protein does not necessarily improve longevity of a dog with kidney disease. When comparing diets and evaluating the amount of phosphorus in the diet, it is important to factor in the calories per ounce. One diet may be lower in phosphorus but if it is also lower in calories, a dog will need to consume more of it (and hence more phosphorus) in order to meet it’s daily energy requirements.
Here is a useful chart I found containing phosphorus amount comparisons for different ingredients.
Phosphorus Binders
Based on my research, there are 4 main types of phosphorus binders that are commonly used in dogs with kidney disease: Aluminum Hydroxide, Calcium-based binder, Lanthanum & Chitosan.
- Aluminum Hydroxide is an effective phosphorus binder that is commonly used in dogs with elevated phosphorus levels. This is the phosphorus binder I give Arlo. It has been difficult finding consensus on dosage amount for aluminum hydroxide, so work with with your vet to determine the starting dosage and use repeated bloodwork to determine effectiveness and make adjustments. Aluminum hydroxide is generally considered stable but there is a risk that long-term use of aluminum-based binders could lead to aluminum toxicity. Two common products containing Aluminum Hydroxide are:
- Calcium Carbonate and Calcium Acetate are two commonly used phosphorus binders. These are often not the first-choice phosphorus binders as they are not as effective as other phosphorus binders. Using calcium-based binders can also potentially lead to hypercalcemia. I have read that some owners like to give their dogs crushed egg shells which are high in calcium carbonate. Others buy human-grade Calcium Carbonate supplements. Two common products containing Calcium-based phosphorus binders are:
- Epakitin - Contains Calcium Carbonate, as well as Chitosan, another type of phosphorus binder
- Naraquin - Contains Calcium Acetate, as well as Chitosan
- Lanthanum Carbonate is a newer type of phosphorus binder. It requires a prescription and seems to be very expensive and not easily available. Fosrenol is a drug available in the US containing lanthanum carbonate. Vets from research hospitals may recommend trying Lanthanum if other binders do not effectively control phosphorus levels.
- Chitosan is found in the shells of crabs and shrimp and can bind with phosphorus to limit absorption. Epakitin and Naraquin mentioned above both contain Chitosan.
A combination of phosphorus binders may be used if one type does not effectively control phosphorus levels. However, it is important to work closely with your vet to determine the appropriate dosage of phosphorus binder to add to your dog’s food to avoid side effects and other issues.