Kidney Anatomy

The kidneys are a pair of bean-shaped organs located on either side of the spine just below the waist. Each one is about the size of your fist. In color, the kidneys are purplish-brown.

The kidneys are designed to:

  • Filter the blood
  • Remove wastes from the body
  • Regulate the chemical and water balances of the blood in various ways to help control blood pressure. Some of these chemicals cause the body to retain water; others cause the body to release water
  • Produce erythropoietin. It stimulates the bone marrow to produce and release red blood cells. People who have failing kidneys often have
    anemia, because their bodies are not making enough erythropoietin.

One of the major roles of the kidneys is to keep the entire body in a stable state (homeostasis). Among the factors involved in doing this are controlling the chemical and minerals in the blood (electrolytes), controlling how acidic the body is, controlling the volume of blood flowing through the body and controlling blood pressure.

The innermost part of the kidney is called the renal medulla. It is divided into 10 to 12 sections. These sections are known as the renal pyramids. The tip of each pyramid empties into a calyx. The calyces then empty into the renal pelvis. From there, urine is carries into the bladder by the ureter.

Blood is carried into the kidneys by the renal arteries. The renal arteries branch off from the abdominal aorta.

Within each kidney are more than a million nephrons. These filter the blood and then reabsorb water and selected chemicals that the body needs. Many kidney diseases attack the nephrons and cause them to lose their filtering capabilities. High levels of sugar in the blood from diabetes can damage the nephrons. This is called diabetic nephropathy. High blood pressure can damage the small blood vessels in the kidneys. Chemicals that are absorbed by the kidneys for use in the body include sodium, glucose (the sugar that is in blood), water and amino acids. The body uses amino acids to make proteins.

Chemicals that the body cannot use -- such as ammonia, drugs, hormones and other substances -- go into the urine.

The urine is moved from the nephrons into the renal pyramids through the calyces into the renal pelvis to the ureter. The ureter carries the urine to the bladder. The bladder moves the urine outside the body through the urethra.

In the meantime, the blood is being carried by the veins back to the heart to pick up oxygen.

Most people have two kidneys. Some people have a horseshoe kidney. This is where the two kidneys are fused into a horseshoe shape.

Diseases such as diabetes, high blood pressure (hypertension), glomerulonephritis and polycystic kidney disease can cause the kidneys to fail. It is possible to live with only one kidney because the kidney that remains compensates for the loss of the second kidney.

If both kidneys fail, a kidney transplant may be needed. This allows the function of the kidneys to be replaced most effectively. At the Minimally Invasive Urology Program and the Kidney and Pancreas Transplant Center minimally invasive techniques are used when a living donor is allowing his or her kidney to be used to help a person who needs a kidney transplant. These techniques are less painful and allow for faster healing than traditional, open surgical techniques.

The Minimally Invasive Urology Program also treats: