Understanding Kidney Disease -- the Basics

What Is Kidney Disease?

The kidneys are two organs located in your midsection on either side of your spine in the middle of your back, just above the waist. They clean your blood, keep the balance of salt and minerals in your blood, and help control blood pressure.

When your kidneys are damaged, waste products and fluid can build up in your body, causing swelling in your ankles, vomiting, weakness, poor sleep, and shortness of breath. If you don't treat them, diseased kidneys may eventually stop working completely. Loss of kidney function is a serious -- and potentially fatal -- condition.

Healthy kidneys:

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


What Causes Acute Kidney Injury?

Doctors call the sudden loss of kidney function "acute kidney injury" or "acute renal failure" (ARF). It has three main causes:

  • Lack of blood flow to the kidneys
  • Direct damage to the kidneys themselves
  • Urine backed up in the kidneys

These can happen when you:

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

What Causes Chronic Kidney Disease?

Kidneys that don't work well for longer than 3 months is called chronic kidney disease (CKD). It's dangerous, because you may not have any symptoms until a lot of damage, that often can't be repaired, has happened.


Diabetes (types 1 and 2) and high blood pressure are the most common causes.

Immune system diseases, such as lupus, and long-term viral illnesses, such as HIV/AIDS, hepatitis B, and hepatitis C, can also cause problems.

Urinary tract infections within the kidneys themselves, called pyelonephritis, can lead to scarring as the infection heals. Multiple episodes can lead to kidney damage.

You could have inflammation in the tiny filters (glomeruli) within your kidneys. This can happen after a strep infection.

Polycystic kidney disease, where fluid-filled cysts form in your kidneys, is the most common type of inherited kidney disease.

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 kind of valve between the bladder and urethra. These defects, sometimes found while a baby is still in the womb, can often be repaired with surgery by a urologist.

Drugs and toxins, including long-term use of some medications, such as NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen and naproxen, and intravenous "street" drugs can permanently damage your kidneys. So can being around certain chemicals over time.

WebMD Medical Reference Reviewed by Michael Dansinger, MD on January 09, 2016



National Institute of Diabetes and Digestive and Kidney Disease. 

National Library of Medicine. 

National Kidney Disease Education Program.

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