The Kidneys - Functions / Location

What are the kidneys? Where are they?

The kidneys are two abdominal organs, which are located on the left and right of the spine, well-protected in the back of the abdominal cavity. They are just at or below the ribs. As the liver is also located on the right side, the right kidney is about 3-4 centimeters lower than the left one. A single kidney weighs about 150-250 grams and is about 12 centimeters long and 5 centimeters wide. In order to fulfill their functions of elimination and detoxification, both kidneys must be thoroughly supplied with blood. The kidneys are supplied with arterial blood from the aorta via the so called renal artery (renal refers to the kidney). The renal vein drains the venous blood from the kidney. Together with the ureter, which carries the urine to the bladder, these blood vessels enter the kidney at the hilus.



Upon close examination of the insides of a kidney, you can see various anatomical details with the naked eye. The outer layer of the kidney is called the cortex in which are found the glomeruli (tiny ball-shaped structures composed of capillary blood vessels) and the kidney tubules (tiny tubes). In the inside layers is the so called medulla which is composed of renal pyramids in which the collecting ducts are located. So called renal calices (funnel shaped tubes) lead out of each pyramid into the renal pelvis. The urine then flows out of the renal pelvis through the ureter into the bladder.


What are the functions of the kidneys?

The main task of the kidneys is to clean and filter the blood; they could be seen as the sewage treatment plant of the human body. Despite their small size, they work very hard. In 24 hours about 1500 liters of blood flow through the kidneys where it is cleaned in a filter system. All poisons and waste products which are produced daily in the course of metabolism are filtered out and expelled in the urine. Substances which are important for the body such as proteins or minerals are either not filtered out or are returned to the blood.


Additionally, the kidneys must carry out a number of other important tasks. They regulate the balance of salt and water in the body, the blood pressure, the production of various hormones (e.g. erythropoietins which stimulate the development of red blood cells) and the pH level of the blood.

Urine Production

The filter system of a kidney is composed of over 1 million tiny filter units, the so called nephrons. Each nephron has a filtration body (glomerulus) and a tubule (a small tube), and filters the blood which flows through it (like a coffee filter) and thusly cleanses it. The total length of all neprons, if strung out together, would be about 25 kilometers! The greater part of the liquid which has thusly been filtered out of the blood (primary urine) is returned to the blood via various transportation mechanisms. From the approximately 180 liters of liquid which are filtrated out of the blood daily, there are only about 2 or 3 liters of urine which land in the bladder. 



My kidney is ill and I need kidney transplant.
What kind of testing and examinations await me?

To be recognized as a candidate for kidney transplantation by Eurotransplant, the patient's entire health situation must be examined and evaluated. For this many examinations are necessary. These can be done in various departments of our University Clinic or by a local specialist. The patient will be cared for and accompanied by our experienced team and the nephrologist in charge of his or her case throughout the examinations and planning thereof.



Your health insurance will cover the costs of these examinations.

The following list should give you an overview of the mandatory examinations:

  • Blood testing
  • ECG, exercise ECG, heart sonogram
  • Lung x-rays
  • Abdominal sonogram (abdominal organs)
  • Vascular sonogram (neck, pelvis, legs)
  • Ear, nose, and throat examination
  • Dental examination
  • Dermatologist examination
  • Eye doctor examination
  • Gynecology examination
  • Urology examination



Depending upon the kind of disease, the test results, and the patient's age, additional tests and examinations could be required in order to deepen the diagnostics. Some examples follow: 


  • Lung function test
  • Heart catheter examination
  • Stomach or intestinal endoscopy
  • Computer Tomography / Magnetic Resonance Tomography