Description, Causes and Risk Factors:
Renal osteodystrophy, the term used to describe the skeletal complications of end-stage renal disease, is a multifactorial disorder of bone remodeling. Renal osteodystrophy is a bone disease that occurs when your kidneys fail to maintain the proper levels of calcium and phosphorus in your blood. It's a common problem in people with kidney disease and affects 90 percent of dialysis patients.
Renal osteodystrophy is most serious in children because their bones are still growing. The condition slows bone growth and causes deformities. One such deformity occurs when the legs bend inward toward each other or outward away from each other; this deformity is referred to as "renal rickets." Another important consequence is short stature. Symptoms can be seen in growing children with renal disease even before they start dialysis.
The bone changes from renal osteodystrophy can begin many years before symptoms appear in adults with kidney disease. For this reason, it's called the "silent crippler." The symptoms of renal osteodystrophy aren't usually seen in adults until they have been on dialysis for several years. Older patients and women who have gone through menopause are at greater risk for this disease because they're already vulnerable to osteoporosis, another bone disease, even without kidney disease. If left untreated, the bones gradually become thin and weak, and a person with renal osteodystrophy may begin to feel bone and joint pain. There's also an increased risk of bone fractures.
In healthy adults, bone tissue is continually being remodeled and rebuilt. The kidneys play an important role in maintaining healthy bone mass and structure because one of their jobs is to balance calcium and phosphorus levels in the blood.
Calcium is a mineral that builds and strengthens bones. It's found in many foods, particularly milk and other dairy products. If calcium levels in the blood become too low, four small glands in the neck called the parathyroid glands release a hormone called parathyroid hormone (PTH). This hormone draws calcium from the bones to raise blood calcium levels. Too much PTH in the blood will remove too much calcium from the bones; over time, the constant removal of calcium weakens the bones.
Phosphorus, which is found in most foods, also helps regulate calcium levels in the bones. Healthy kidneys remove excess phosphorus from the blood. When the kidneys stop working normally, phosphorus levels in the blood can become too high, leading to lower levels of calcium in the blood and resulting in the loss of calcium from the bones.
Healthy kidneys produce calcitriol, a form of vitamin D, to help the body absorb dietary calcium into the blood and the bones. If calcitriol levels drop too low, PTH levels increase, and calcium is removed from the bones. Calcitriol and PTH work together to keep calcium balance normal and bones healthy. In a patient with kidney failure, the kidneys stop making calcitriol. The body then can't absorb calcium from food and starts removing it from the bones.
Renal osteodystrophy is often called the "silent crippler" since kidney patients may not experience symptoms at all. Usually symptoms do not occur until a patient has been on dialysis for a few years. Typical symptoms can be:
Early indicators of renal osteodystrophy include high phosphorus and/or high parathyroid hormone (PTH) levels, red eyes, itching and sores from calcium-phosphorus deposits.
Children with kidney disease can be especially affected by renal osteodystrophy because their bones are still growing. Even before children with kidney disease begin dialysis, they can have symptoms of renal osteodystrophy. This bone disease can lead to slow bone growth in children and can cause "renal rickets" where the leg bones grow either bowed toward each other or away from each other. Children with renal osteodystrophy are also prone to be shorter in stature.
Because there are different types of bone disease, your doctor will test you specifically for renal osteodystrophy if you are experiencing symptoms such as bone pain or deposits of calcium under your skin or if blood test suggests that you suffer from renal osteodystrophy. Testing for renal osteodystrophy involves taking a blood sample to measure your levels of calcium, phosphorus and parathyroid hormone (PTH). If you are on dialysis, calcium and phosphorus tests are done on a monthly basis (or sometimes more frequently). PTH is measured quarterly for most patients — although testing may be done more frequently for people just starting vitamin D therapy or those with severe bone disease while the health care team is determining the correct dosage of vitamin D. Your renal dietitian will review your lab results with you and recommend treatments such as changes in your diet or change your phosphorus binder prescription. Depending on your situation and risk factors, your doctor may also take a bone biopsy from your hip to see how dense your bones are. After reviewing the results of your tests, your doctor will recommend an appropriate treatment regimen if renal osteodystrophy is found.
The goal of treating renal osteodystrophy is to restore balance between calcium, parathyroid hormone (PTH), phosphorus and vitamin D in the body. Renal osteodystrophy can be managed with phosphorus binders, activated vitamin D and a low-phosphorus diet. If you have a high level of PTH in your blood, it is important to bring it back to a normal level to prevent calcium loss from your bones. Medicines to treat renal osteodystrophy can be given in pill form, but are usually given intravenously during dialysis treatments for people on in-center hemodialysis. These medicines are only used in patients with kidney disease, since normal kidneys are able to activate the vitamin D that is normally made by the body. Another drug that may be used acts directly on the parathyroid glands to block PTH release. In severe cases the parathyroid glands may be surgically removed.
In addition to a low-phosphorus diet and taking prescribed medicines, exercise can also help increase your bone strength. Check with your doctor before beginning an exercise program.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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