The paired kidney is the body's purifier. Read more about the kidney: location, anatomy and important kidney diseases!


The kidney (Latin: ren) can also be called the purification plant of the human body. The paired organ cleanses the body of harmful substances by filtering the blood and directing the pollutants outward with the formed urine. Other functions include the regulation of blood pressure, the water and salt balance and the acid-base balance. Read all about the kidneys here: Location, structure and important diseases!

Product Overview


  • What is the kidney?

  • What function does the kidney have?

  • Where is the kidney?

  • What problems can the kidney cause?

What is the kidney?

The kidney is a red-brown organ, which occurs in pairs in the body. Both organs have a bean shape. Its longitudinal diameter is ten to twelve centimeters, the transverse diameter five to six centimeters and the thickness about four centimeters. A kidney weighs between 120 and 200 grams. The right one is usually a bit smaller and lighter than the left one.

Each kidney has two surfaces (anterior and posterior surface, facies anterior and posterior), two poles (upper and lower renal pole) and two margins (inner and outer margin, medial and lateral margins).

In the middle, inwardly curved edge of the organ lies a niche-shaped depression, the so-called renal portal (-hilus). Through them runs the renal artery (renal artery) and vein (vena renalis): The artery leads with waste laden blood into the organ, the vein brings the purified blood out again. Entry and exit points of nerves and lymphatics are also located on the hilum of the kidney.

Construction of three zones

The kidney anatomy in longitudinal section has three zones:

Inside is the renal pelvis, the collecting space for the developing urine. The fine-grained renal medulla (medulla renalis) joins the outside. On the far side lies the renal cortex (cortex renalis), which appears brighter than the medulla layer.

The medulla layer is subdivided into eight to sixteen conical marrow pyramids by extensions of the cortex (Columnae renalis). The tips of these marrow pyramids point towards Hilus.
Conversely, the marrow continues in so-called medullary rays into the cortex.

The tips of the cone-shaped medullary pyramids are called renal papillae and each have a microscopic opening. These lead into a small cavity, the kidney goblet.
In the calices, the finished urine is collected and forwarded to the renal pelvis.

Mark and bark together form the renal parenchyma. It contains about 1 to 1.4 million small filter units called nephrons. There are also specialized cells that produce the hormones renin and erythropoietin. Renin is important for the regulation of blood pressure, erythropoietin for the formation of red blood cells.

Connective tissue capsule and fat layer

Each kidney is covered by a tough capsule, a transparent connective tissue envelope. Around them lies a thick layer of fatty tissue surrounded by another thin connective tissue envelope.

The fat and connective tissue capsule protects the sensitive organ against impact injuries and anchors it to the posterior abdominal wall.


Nephrones are the functional units of the kidney. Structure of these filter units For more information on the structure of the nephrone, see the article Nephron.

What function does the kidney have?

Everything important about the renal function can be found in the subtext kidney function.

How do you recognize a pyelonephritis and who is particularly at risk?

Where is the kidney?

Both kidneys lie outside the abdominal cavity, in the so-called retroperitoneal space - behind the peritoneum. They are thus not enclosed by peritoneum.

Where are the kidneys exactly?

They are located between the posterior wall of the peritoneum and the back muscles (psoas muscle and quadratus lumborum muscle). The exact position depends on the breathing and the body position. The caused by breathing height difference of the two organs makes up three centimeters.

The kidneys range from about the twelfth thoracic vertebra to the third lumbar vertebra. Because of the liver (in the right upper abdomen), the right specimen is on average up to two centimeters deeper than the left.

The right kidney is adjacent to the liver, duodenum, and right bend of the colon (right colonic flexure). On the left, there are neighborly relations to the stomach and spleen, to the tail of the pancreas (pancreatic tail), to the descending part of the large intestine (descending colon), to the splenic vein and splenic artery.

One adrenal gland (Glandula suprarenalis) sits on both upper organ poles. It is an important hormone gland.

Before and behind each kidney, connective tissue densifications, so-called fascia, are found. They pull from the diaphragm to the intestinal ridge.

The architectural unit of kidney, fat capsule and fascia is often summarized under the term kidney stock.

What problems can the kidney cause?

Diseases of the kidney (renal diseases) are expressed by a variety of different symptoms. These result from changes in the body that result from impaired organ function.

Possible complaints in renal diseases are, for example, dull back pain and colicky back pain with radiation in the direction of the bladder. The urine may turn red or cloudy and smell unpleasant. Foam formation in the urine can often be observed in renal diseases.

In addition, the urine production can be reduced so that the patients excrete only little or no urine (anuria). Swelling of the eyelids or ankles (edema) may also indicate a renal disease.

In the further course of such a disease, additional symptoms may be added. These include, for example, loss of appetite, nausea, vomiting, general feeling of weakness, pale or greyish skin color, shortness of breath and water retention (especially in the legs). Itching of the skin, bad breath or metallic taste in the mouth as well as a strong acidic body odor can accompany a renal disease.

The most important renal diseases are:

  • Kidney stones (nephrolithiasis)
  • Kidney (pelvic) inflammation (glomerulonephritis, pyelonephritis)
  • Organ damage caused by medications such as certain painkillers
  • Organ malformations
  • Renal artery calcification
  • Acute and chronic renal failure (renal insufficiency)
  • benign and malignant tumors

If both organs can no longer fulfill their function due to illness (insufficiency), the toxic substances accumulate in the body because they are no longer (sufficiently) disposed of through the urine. Then the blood must be purified in another way to prevent life-threatening poisoning of the body:

One option is to wash the blood; The blood of the patient is either filtered via a machine (hemodialysis) or his own peritoneum (peritoneal dialysis). The second option is to transplant a healthy one kidney from an organ donor.

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    Nine tips for healthy kidneys

    Kidneys are heavy laborers. Among other things, they filter and detoxify the entire blood volume of the body around 300 times a day - that's up to 15 baths of blood. Everybody can do something to keep the organs fit. Here are nine simple tips to keep your kidneys healthy.

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    Keep yourself fit

    Sport improves cardiovascular function and protects your kidneys as well. Find a sport that you enjoy. So, exercise does not become a chore. The rule is: Exercise regularly and in smaller units than about every two weeks for three hours at a time.

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    Control your blood sugar

    High blood glucose levels are generally bad for the blood vessels. The sugar also forms complexes with proteins, which are deposited in tiny blood vessel nodules of the kidneys called glomeruli. Regularly checking that the values โ€‹โ€‹are in order helps to recognize a creeping developing diabetes in good time. Those who already suffer from diabetes also protect their kidneys with good blood sugar levels.

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    Measure your blood pressure

    High blood pressure damages the vessels considerably in the long run. Even if you do not feel it: Increased values โ€‹โ€‹are no trifle, even for the kidneys.

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    Eat healthy

    A balanced diet provides your body with all the essential vitamins and minerals. Caution salt: Large amounts of the popular condiment strain the kidneys too much. Make sure you eat low in salt. Spice up with fresh herbs!

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    Drink enough

    Kidneys need water to work properly - this is the only way to get enough urine out of the body, and therefore pollutants. It should be 1.5 liters a day - even more in sports and heat.

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    Avoid cigarettes

    Smoking is poison, especially for the vessels. If you succeed in giving up cigarettes, you also do something for your kidneys. Because the organs have to filter the toxins contained in the tobacco from the blood - and that is a big burden.

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    Avoid being overweight

    Obesity is a risk factor for many diseases - including kidney failure. The organs benefit from a not too lush body shape. Therefore, try to lose extra pounds. This works best with a healthy diet and regular exercise.

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    Take painkillers only for a short time

    The kidneys as filter organs have the task to remove drug substances from the body. In particular, they respond sensitively to a continuous shot by painkillers.Therefore, take especially over-the-counter analgesics only for a short time.

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    Have your kidney function checked

    Monitoring kidney function is particularly useful if you belong to a high-risk group. These include all people over the age of 60, diabetics, people with high blood pressure, overweight people and people with kidney disease family members.

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