Renal Osteodystrophy

What is renal osteodystrophy?

Renal osteodystrophy is a bone disease that occurs in adults and children with chronic kidney disease.

Your kidneys help regulate mineral levels of calcium and phosphorus in your blood. They also produce calcitriol hormone by activating vitamin D to keep your bones strong and healthy. When your kidneys fail or aren’t functioning as well, they can’t maintain proper levels of these minerals and calcitriol hormone. This can weaken your bones and lead to fractures.

What minerals and hormones are important for bone health?

The minerals and hormones that help keep your bones healthy include:

• Calcium: Your bones are the calcium bank for your body. Calcium makes your bones strong. It also aids in many other bodily processes, such as nerve and muscle function. Your kidneys help balance calcium levels in your blood.
• Phosphorus: Along with calcium, phosphorus is a key component of bone. Your kidneys remove excess phosphorus from your body to make sure your blood contains the right balance of calcium and phosphorus.
• Calcitriol: This hormone is an active form of vitamin D made by your kidneys. It helps control how much calcium you absorb from the food you eat and the function of your parathyroid glands.
• Fibroblast growth factor (FGF): Fibroblast growth factor 23 (FGF23) is a hormone produced in your bones. It helps control levels of phosphorus and vitamin D. People with chronic kidney disease tend to have higher levels of FGF23.
• Parathyroid hormone: Your parathyroid glands produce this hormone. Its role is to maintain stable calcium levels in your blood when your body needs it by activating calcium resorption from your bones. You have four parathyroid glands in your neck behind your thyroid gland.

What are the types of renal osteodystrophy?

Bone growth occurs during childhood. As an adult, your bones are in a constant state of turnover and renewal. Old bone tissue breaks down and new tissue takes its place.

Renal osteodystrophy can occur when bone turnover is too fast or too slow. The four main types of renal osteodystrophy include:

• Osteitis fibrosa: Bone tissue breaks down too fast and leads to higher-than-normal levels of parathyroid hormone (hyperparathyroidism).
• Osteomalacia: Bone tissue breaks down but new bone doesn't form, leaving it spongy and weak. Osteomalacia can cause low levels of vitamin D, heavy metal toxicity and overproduction of FGF23 by certain cancers.
• Adynamic bone disease: Bone tissue doesn't renew itself as it should. This condition is the result of lower levels of parathyroid hormone.
• Mixed renal osteodystrophy: Includes signs of osteitis fibrosa and osteomalacia.

Osteitis Fibrosa

People with chronic kidney disease often have higher parathyroid hormone levels. Parathyroid hormone balances calcium levels in your blood by transferring calcium from your bones to your blood. But when parathyroid hormone levels are too high, it can pull too much calcium from your bones. When this occurs, fibrous cysts can form in your bones, making them weak.

Some factors that cause high parathyroid hormone levels include:

• Decreased calcitriol: Damaged kidneys don’t make calcitriol as they should. This leads to increased production of parathyroid hormone.
• Elevated levels of FGF23: This may be an early sign of kidney disease and could be a response by your bones to prevent high phosphorus levels.
• Increased phosphorus: With chronic kidney disease, your kidneys don't remove phosphorus and it builds up in your blood. This stimulates the production of parathyroid hormone.

Osteomalacia

This condition is the result of low levels of vitamin D, which is common in people with chronic kidney disease.

Metal toxicity can also lead to osteomalacia. Metals such as aluminum can interfere with bone formation and maintenance. Aluminum is an ingredient in some older phosphorus-binder medications. These medications are no longer recommended for use in people with chronic kidney disease or terminal kidney disease on dialysis. People with kidney disease take phosphorus binders with meals to control high phosphorus levels in their blood. The phosphorus binders prevent phosphorus in their food from entering their bloodstream. Non-aluminum phosphorus binders are now the preferred drugs used to control high phosphorus levels.

Overproduction of FGF23 by certain cancers may cause osteomalacia of malignancy leading to bone fractures.

Adynamic Bone Disease

Bone tissue doesn’t renew itself as it should in people with advanced kidney disease or terminal kidney disease on dialysis. The main cause of adynamic bone disease is excess calcium and vitamin D. Treatment for kidney disease may involve supplementation with high levels of calcium and vitamin D. While this treatment can help prevent renal osteodystrophy associated with high bone turnover, it can also suppress parathyroid hormone levels.

Other causes of adynamic bone disease include:

• Continuous peritoneal dialysis: This is a type of dialysis where the filtration occurs in your abdomen. It differs from hemodialysis, which filters your blood through a port, usually in your arm. Some peritoneal dialysis fluids contain high levels of calcium. These can reduce parathyroid hormone levels.
• Diabetes: Elevated glucose and decreased insulin levels with diabetes can reduce parathyroid hormone production.

What is chronic kidney disease mineral and bone disorder (CKD-MBD)?

An imbalance in minerals and hormones can also affect your heart and blood vessels. CKD-MBD is an umbrella term that includes renal osteodystrophy and related cardiovascular disease.

Excess calcium and phosphorus in your blood can cause cardiovascular disease through a process called calcification. Calcium builds up on the inside of your blood vessels. This can lead to hardening of your blood vessels (atherosclerosis), high blood pressure, heart attack and stroke.

How common is renal osteodystrophy?

Approximately 15% of U.S. adults have chronic kidney disease. Most people who have it are likely to have some degree of renal osteodystrophy. Bone damage becomes more severe after kidney failure and long-term dialysis.

What causes renal osteodystrophy?

Chronic kidney disease causes renal osteodystrophy. Kidney disease disrupts mineral and hormone levels and normal bone turnover. High and low bone turnover can weaken your bones.

What are the symptoms of renal osteodystrophy?

The main symptoms are bone pain and fractures. Some people with early forms of the disease may not have any symptoms.

Children with kidney disease may experience growth delays that are due to renal osteodystrophy. It can also cause skeletal deformities known as rickets. This is the childhood form of osteomalacia.

How is renal osteodystrophy diagnosed?

Your healthcare provider will review your symptoms, along with your medical and family history. They'll also perform a physical exam.

Tests providers use to diagnose this condition include:

• Blood tests: These include measurements of calcium, phosphorus, vitamin D and parathyroid hormone. Blood tests can also measure other markers, such as alkaline phosphatase, that help with bone turnover (regeneration). If you have chronic kidney disease, your provider will perform blood tests routinely to look for changes in these levels.
• Bone biopsy: A biopsy involves collection of a small sample of tissue for laboratory analysis. Bone biopsies can help your provider check bone density and structure, but they're rarely used.
• Bone density test: Also called a DEXA scan, this test measures the strength of your bones and risk of fracture.
• Imaging tests: X-rays, CT scans and MRIs can help your provider assess bone changes. Providers also use CT scans and echocardiograms to look for calcification in your blood vessels.

How is renal osteodystrophy treated?

Your treatment will depend on the extent of bone damage and kidney disease and whether bone turnover is high or low. The main types of treatments include:

• Dietary changes: Your healthcare provider may recommend a low phosphorus diet. This includes limiting processed and packaged foods which are often high in added phosphorus. You may also have to limit foods that have naturally high levels of phosphorus if you have advanced kidney disease.
• Medications and supplements: These can help balance mineral and hormone levels. They include calcium and vitamin D supplements, parathyroid hormone-lowering drugs and phosphorus binders. Your provider may recommend non-calcium phosphorus binders to reduce phosphorus levels without increasing calcium. Persistent high calcium levels can lead to low bone turnover and adynamic bone disease.
• Parathyroid surgery: Surgery is an option if other treatments aren't effective. It involves removal of one or more of your parathyroid glands (parathyroidectomy). Providers usually leave at least one of your parathyroid glands in place. This can help prevent low parathyroid levels and adynamic bone disease.

Your provider will also help you manage kidney disease. Keeping up with your treatment plan can help you prevent further bone damage.

How can I prevent renal osteodystrophy?

You can't prevent renal osteodystrophy, but you can slow down its progression by managing chronic kidney disease. Take your medications, follow your prescribed diet and complete your dialysis treatments. Exercising, quitting smoking and limiting alcohol can also help.

What can I expect if I have renal osteodystrophy?

There's no cure except for a kidney transplant. People with chronic kidney disease lose kidney function gradually. Many progress to kidney failure and dialysis. Renal osteodystrophy is a common complication.

Many people with chronic kidney disease also develop heart disease. It's the most common cause of death among people with kidney failure.

Your healthcare provider will track your mineral and hormone levels. They’ll make treatment recommendations to help protect your bone and heart health.

When should I talk to my healthcare provider?

If you have chronic kidney disease, talk to your healthcare provider if you have any bone pain. This may be a sign of renal osteodystrophy.

Most people with chronic kidney disease don’t know they have it until it becomes advanced. Routine checkups with your provider can help you detect kidney disease early. With early detection, you can take steps to slow its progression. This is especially important if you have any risk factors for kidney disease, such as:

• Carrying excess weight.
• Diabetes.
• Family history of chronic kidney disease.
• Heart disease.
• High blood pressure.

A note from Cleveland Clinic

Renal osteodystrophy is one of the many complications of chronic kidney disease. It can weaken your bones and cause bone pain and fractures. If you have kidney disease, your healthcare provider will check the levels of minerals and hormones in your blood regularly. Treatments can help correct any imbalances in these substances. If you have chronic kidney disease, follow your provider’s guidance for your diet, medications and dialysis. You can’t cure this condition, but you can take steps to slow its progression and maintain a good quality of life.