Humans have two kidneys so that if one of them fails, the body is still able to maintain basic functions. This redundancy of one of the two kidneys allows one kidney to take over the function of the other if it is damaged, diseased or stops functioning for other reasons.
What is the function of the kidneys in the body?
The kidneys are filtering organs and are responsible for continuously filtering our blood and ridding it of waste and excess fluid.
The actual filtering takes place in the nephrons, the functional areas of the kidneys. Each kidney consists of about one million nephrons. When the blood is filtered, urine is produced as a waste product, also known as urine, which is transported via the ureters into the urinary bladder and then excreted via the urethra. Due to their filtering function, the kidneys are also significantly involved in the regulation of electrolytes such as sodium, calcium and potassium, as well as in the regulation of the acid-base balance, blood pressure and blood volume.
Where in the body are the kidneys located and how are they structured?
Almost all people have two kidneys, which are arranged in pairs and are located on either side of the spine in the back of the abdomen just below the ribs. In adult humans, the kidneys are between 10 and 12 cm long, 5 to 5 cm wide and about 3 cm thick. As a rule, the kidneys are bean-shaped. They are surrounded by a connective tissue-like capsule, and are also protected against injury by a layer of fat and the renal fascia.
What happens when a kidney breaks down?
The fact that almost all people have two kidneys is an evolutionary safety measure. This ensures that the body can only survive with one functioning kidney and that it can maintain its basic functions. This means that one kidney is theoretically able to take over all the tasks of the other kidney and the body is affected little if at all by the absence of one of the two kidneys.
Can the kidneys regenerate themselves?
To a certain extent, the kidneys are able to regenerate and even adapt their function to changing conditions. For example, if part of a kidney is lost or damaged, the remaining nephrons of that kidney can hypertrophy – increase in size – and increase their function to compensate for the lost nephrons. Complete regeneration is not possible and compensation can only occur to a certain extent.
In what cases do people have only one kidney?
There are many different reasons why people have only one kidney. These include congenital malformations, injuries, diseases or living donations. Some people are born with only one kidney. This congenital anomaly is called renal agenesis and in most cases the remaining kidney can compensate for the absence. In other cases, people need to have a kidney surgically removed because of disease or injury. This operation is called a nephrectomy. Reasons for a nephrectomy can include kidney cancer, severe kidney infections, kidney stones or trauma, i.e. injury. Another reason why some people only have one kidney is because they voluntarily donate a kidney to another person who is suffering from complete kidney failure.
Voluntary kidney donation
If a person with two healthy kidneys decides to donate one of them to another person, this is possible because of the kidneys‘ compensatory ability. Such a living donation can be life-saving for people with kidney failure or, in any case, significantly improves the recipient’s quality of life, as he or she will no longer be dependent on dialysis and medication.
What is dialysis?
Dialysis is a medical treatment that relieves the kidneys of their work. It involves cleansing the patient’s blood at regular intervals. If a transplant is not possible, dialysis treatment can be used as a replacement therapy to partially take over the function of the kidneys. By removing waste products, excess fluids and electrolytes from the blood, dialysis ensures that the body’s internal balance is maintained. There are two main types of dialysis: haemodialysis, where the patient’s blood is filtered through an artificial kidney or dialysis machine, and peritoneal dialysis, where the body’s own abdominal cavity and peritoneum are used as a filter membrane.
How can kidney disease be prevented?
To minimise risk factors for kidney disease, diet is a particularly important factor. Healthy foods with little fat and salt as well as sufficient fluid intake play a central role in maintaining kidney health.
Regular blood pressure control and the prevention of diabetes are also important.
Last but not least, alcohol and nicotine also contribute to damaging the kidneys, as does the excessive use of medication or drugs.