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.
Creatinine is a waste product from the normal breakdown of muscle tissue. As creatinine is produced, it's filtered through the kidneys and excreted in urine. Doctors measure the blood creatinine level as a test of kidney function. The kidneys' ability to handle creatinine is called the creatinine clearance rate, which helps to estimate the glomerular filtration rate (GFR) -- the rate of blood flow through the kidneys.
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 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 chemical 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; overuse of NSAIDs (nonsteroidal anti-inflammatory drugs), such as ibuprofen and naproxen; and use of intravenous “street” drugs.