The kidneys are two bean-shaped organs that extract waste from blood, balance body fluids, form urine, and aid in other important functions of the body.

They reside against the back muscles in the upper abdominal cavity. They sit opposite each other on both sides of the spine. The right kidney sits a little bit lower than the left to accommodate the liver.

When it comes to components of the urinary system, the kidneys are multi-talented powerhouses of activity. Some of the core functions of the kidneys include:

• Waste excretion: There are many things your body doesn’t want inside of it, and the kidneys help get rid of some of them. The kidneys filter out toxins, excess salts, and urea, a nitrogen-based waste created by cell metabolism. Urea is synthesized in the liver and transported through the blood to the kidneys for removal.
• Water level balancing: As the kidneys are key in the production of urine, they react to changes in the body’s water level throughout the day. As water intake decreases, the kidneys adjust accordingly and leave water in the body instead of helping excrete it.
• Blood pressure regulation: The kidneys need constant pressure to filter the blood. When it drops too low, the kidneys increase the pressure. One way is by producing a blood vessel-constricting protein (angiotensin) that also signals the body to retain sodium and water. Both the constriction and retention help restore normal blood pressure.
• Red blood cell regulation: When the kidneys don’t get enough oxygen, they send out a distress call in the form of erythropoietin, a hormone that stimulates the bone marrow to produce more oxygen-carrying red blood cells.
• Acid regulation: As cells metabolize, they produce acids. Foods we eat can either increase the acid in our body or neutralize it. If the body is to function properly, it needs to keep a healthy balance of these chemicals. The kidneys do that, too.

Most people are born with two kidneys, but many people can live on just one. Kidney transplant surgeries with live donors are common medical procedures today.

Because of all of the vital functions the kidneys perform and the toxins they encounter, the kidneys are susceptible to various problems.

Acute kidney failure is a condition in which the kidneys suddenly lose their ability to function properly. This can occur for many reasons, including:

• Infection
• Blood-clotting disorders
• Decreased blood flow caused by low blood pressure
• Acute tubular necrosis, or death of the tubular cells that deliver urine to the ureters
• Autoimmune kidney disorders
• Urinary tract infections
• Complications from pregnancy