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Understanding Kidney Disease -- the Basics

What Is Kidney Disease?

The kidneys are two organs located on either side of your spine in the middle of your back, just above the waist. They perform several life-sustaining roles: They cleanse your blood by removing waste and excess fluid, maintain the balance of salt and minerals in your blood, and help regulate blood pressure.

When the kidneys become damaged, waste products and fluid can build up in the body, causing swelling in your ankles, vomiting, weakness, poor sleep, and shortness of breath. If left untreated, diseased kidneys may eventually stop functioning completely. Loss of kidney function is a serious -- and potentially fatal -- condition.

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Healthy kidneys handle several specific roles. Healthy kidneys:

  • Maintain a balance of water and concentration of minerals, such as sodium, potassium, and phosphorus, in your blood
  • Remove waste by-products from the blood after digestion, muscle activity, and exposure to chemicals or medications
  • Produce renin, an enzyme that helps regulate blood pressure
  • Produce erythropoietin, which stimulates red blood cell production
  • Produce an active form of vitamin D, needed for bone health

What Causes Acute Kidney Injury?

The sudden loss of kidney function is called acute kidney injury, also known as acute renal failure (ARF). ARF can occur following:

  • A traumatic injury with blood loss
  • The sudden reduction of blood flow to the kidneys
  • Damage to the kidneys from shock during a severe infection called sepsis
  • Obstruction of urine flow, such as with an enlarged prostate
  • Damage from certain drugs or toxins
  • Pregnancy complications, such as eclampsia and pre-eclampsia, or related HELLP Syndrome

Marathon runners and other athletes who don't drink enough fluids while competing in long-distance endurance events may suffer acute renal failure due to a sudden breakdown of muscle tissue. This muscle breakdown releases a large amount of protein into the bloodstream called myoglobin that can damage the kidneys.

What Causes Chronic Kidney Disease?

Kidney damage and decreased function that lasts longer than 3 months is called chronic kidney disease (CKD). Chronic kidney disease is particularly dangerous, because you may not have any symptoms until considerable, often irreparable, kidney damage has occurred. Diabetes (types 1 and 2) and high blood pressure are the most common causes of CKD. Other causes are:

  • Immune system conditions such as lupus and chronic viral illnesses such as HIV/AIDS, hepatitis B, and hepatitis C
  • Urinary tract infections within the kidneys themselves, called pyelonephritis, can lead to scarring as the infection heals. Multiple episodes can lead to kidney damage.
  • Inflammation in the tiny filters (glomeruli) within the kidneys; this can happen after strep infection and other conditions of unknown cause.
  • Polycystic kidney disease, in which fluid-filled cysts form in the kidneys over time. This is the most common form of inherited kidney disease.
  • Congenital defects, present at birth, are often the result of a urinary tract obstruction or malformation that affects the kidneys; one of the most common involves a valve-like mechanism between the bladder and urethra. These defects, sometimes found while a baby is still in the womb, can often be surgically repaired by a urologist.
  • Drugs and toxins, including long-term exposure to some medications and chemicals, such as NSAIDs (nonsteroidal anti-inflammatory drugs), like ibuprofen and naproxen, and use of intravenous “street” drugs

WebMD Medical Reference

Reviewed by Michael Dansinger, MD on February 12, 2015

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