Phosphorus
Phosphorus is a common mineral that your body needs for energy. It's found in nearly all foods, especially:
- Meats
- Chocolate
- Dairy products
- Cola drinks
- Whole grains
- Dried beans
Like calcium, phosphorus is stored in your bones. Remodeling lets small amounts of it into your blood. Healthy kidneys remove extra phosphorus from your blood. When the kidneys fail, extra phosphorus can bind with calcium to create sharp, calcium phosphate crystals. These crystals can cause itching, skin sores, and worse. In the long term, having the wrong levels of phosphorus in your blood can harm your bones.
Phosphorus is hard to remove with dialysis—and each time you eat, you take in more. The NKF KDOQI guidelines for people on dialysis say that your phosphorus level should be between 3.5 and 5.5 mg/dL. To stay in this range, most people on dialysis need to eat fewer high-phosphorus foods and take some phosphate binders with each meal and snack. These drugs bind with phosphorus and remove it in your stool.
Getting more dialysis by doing daily or nocturnal treatments will remove more phosphorus so you need fewer binders and can eat a more normal diet. In fact, people who do nocturnal HD 5 or 6 nights per week often need phosphate supplements instead of binders, because their treatments work so well.
Using binders and eating fewer high-phosphorus foods can help to keep your bones healthy. To learn more about eating less phosphorus, read Module 9—Nutrition and Fluids for People on Dialysis.
Turning to Stone: Calcified Blood Vessels
You know that too much phosphorus causes itching and bone problems. Having the wrong levels of calcium and phosphorus in your blood can also harm your blood vessels. Calcium phosphate crystals can form in arteries and veins, making them calcify (turning them—quite literally—to stone).
Stone-like blood vessels can't respond to changes in your activity level. Stone-like heart valves can't pump your blood, which can lead to heart failure. Research has found that phosphate binders based on calcium, like Os-Cal® or PhosLo®, can cause this problem or make it worse if calcium levels are already too high. Non-calcium binders, like Renagel® or Fosrenol®, are less likely to make blood vessels calcify, but they cost more.
When you get more dialysis (e.g., daily or nocturnal HD), or if you have a transplant, you don't need to take as many binders. This is something to think about to help you live long and well with kidney failure.
Your doctor can see how much of a problem you have with blood vessel calcification by doing an X-ray, ultrasound, CT scan, or electron beam tomography (EBT). An echocardiogram (echo) test to see how well your heart pumps can also help.
Do you have calcified blood vessels now? Getting more dialysis may help shrink the deposits. Also, osteoporosis drugs called bisphosphonates show some promise for treating this problem.
