Why Are Calcium Levels Low in Renal Failure?

Reviewed on 9/29/2020

Why are calcium levels low in renal failure?

The kidneys help regulate calcium levels in the body.
The kidneys help regulate calcium levels in the body.

There is a complex coordination between the calcium controlling glands (the parathyroid gland), vitamin D (made by the skin or a diet) and the kidneys that is affected once kidney disease progresses.

Renal failure usually causes calcium imbalance.

  • During renal failure, the kidneys may no longer filter out extra phosphorus and remove it from the body or from urine. Over time, phosphorus may increase in the blood. Calcium and phosphorous usually keep each other in check. With the progression of kidney disease, high phosphorus levels may lead to low serum calcium by depositing it onto the bones and other tissues.
  • Vitamin D usually aids in the absorption of calcium from food. Healthy kidneys usually change vitamin D from sunlight and foods into active vitamin D that may help in balancing calcium levels through absorption. When the kidneys fail, there is a short supply of active vitamin D. This causes calcium and phosphorus to get out of balance

It should also be noted that renal failure may also lead to high calcium levels.

  • Parathyroid hormone (PTH) may be produced in large quantities, stimulated by low levels of calcium in the blood. PTH tries to keep the calcium level in the blood normal by increasing calcium absorption from food, but it also takes calcium out of the bones. Eventually the parathyroid glands work so hard they go out of control and may cause persistently high calcium levels.

What is renal failure?

Renal or kidney failure is a condition in which the kidney does not perform its functions properly. This condition may be temporary or permanent. There are two different types of kidney failure

  • Acute kidney injury: It may start suddenly and may be reversible. It may occur due to injury, infections, medication side effects or sometimes preexisting diseases.
  • Chronic/severe kidney disease: It progresses slowly over at least three months and can lead to permanent kidney failure. It may be caused by various medical conditions including diabetes, high blood pressure, hereditary kidney disease, etc. It usually does not produce any symptoms until it progresses to advanced stages.

Stages

  • Stage 1: 90% kidney function is usually preserved. 
  • Stage 2: 60% to 89% kidney function is preserved.
  • Stage 3: Symptoms may include tiredness, puffiness, changes in appetite, dull back pain and urine changes. Kidney functioning may be reduced to 40% to 59%.
  • Stage 4: Patients experience fatigue, swelling, changes in appetite, back pain, changes in urination, hypertension and slowed digestion. Kidney function may be reduced to 15% to 29%.
  • Stage 5: This is end-stage kidney failure. The kidneys are only functioning at less than 15%.

How is renal failure treated?

Early stages of renal failure are usually treated with lifestyle modifications and by controlling underlying causes such as hypertension and diabetes.

When kidney function falls below 10% of normal, the options below may be used

  • Dialysis: This is a way to pump blood through a machine that filters out waste and returns the blood to the body. There are two types of dialysis
    • Hemodialysis: A tube is stuck into one of the veins (the neck, arm or leg) to remove toxins from the blood. This is usually done three times a week for three to four hours at a time.
    • Peritoneal dialysisThis is done through a tube that is placed inside the belly.
  • Kidney transplant: This is a procedure in which a surgeon puts a healthier kidney from another person into the person who has kidney disease. A kidney transplant is the best way to treat many patients with end-stage kidney failure. Kidneys for transplant come from people who have agreed to donate their kidneys when they die (deceased donors) or healthy people (living donors). Living donors are most often family members of the patient. There is a shorter wait time to surgery for a transplant from a living donor. This is because there is a waiting list for the kidneys from deceased donors and not enough donors. Additionally, patients with kidneys donated by living donors live longer (and the kidneys last longer) than those with kidneys from deceased donors or who just stay on dialysis.

What is the life expectancy with kidney failure?

Kidney disease or failure may affect the lifespan. Estimating a timeframe may be complex. In acute cases, death may occur within a few days to a week without treatment. In severe cases, life expectancy may be a few years at most without treatment. However, even people who have complete renal failure may live for years with proper care and regular dialysis treatments. A kidney transplant may also result in a longer survival period.

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References
Medscape Medical Reference

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Kidney Care UK


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