kidney
Dr. Manuela Mai studied medicine at the Universities of Heidelberg and Mannheim. After graduating, she gained clinical experience in gynecology, pathology and clinical pharmacology. She is particularly interested in the broader connections that lead to diseases - also outside of conventional medicine. She completed additional training in classical homeopathy as well as ear and skull acupuncture.
More about the experts All content is checked by medical journalists.The kidney (Latin: ren) can also be referred to as the purification plant of the human body. The paired organ cleanses the body of harmful substances by filtering the blood and directing the harmful substances outwards with the urine that is formed. Other functions include regulating blood pressure, the water and salt balance and the acid-base balance. Here you can read everything you need to know about the kidneys: location, structure and important diseases!
What is the kidney
The kidney is a red-brown organ that occurs in pairs in the body. Both organs are bean-shaped. Their 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, and the right one is usually slightly smaller and lighter than the left.
Each kidney has two surfaces (anterior and posterior surface, facies anterior and posterior), two poles (upper and lower kidney pole) and two edges (inner and outer edge, margo medialis and lateralis).
In the inwardly curved edge of the organ towards the center there is a niche-shaped depression, the so-called kidney gate (-hilus). The renal artery (arteria renalis) and vein (vena renalis) run through them: the artery carries blood laden with waste materials into the organ, the vein brings the purified blood out again. The entry and exit points of nerves and lymph vessels are also located on the hilus of the kidney.
Structure from three zones
The kidney anatomy in longitudinal section has three zones:
Inside is the renal pelvis, the collecting space for the urine that is produced. The finely striped renal medulla (medulla renalis) connects to the outside. The renal cortex is located on the very outside and appears lighter than the medullary layer.
The medullary layer is divided into eight to sixteen conical medullary pyramids by extensions of the cortex (Columnae renalis). The tips of these marrow pyramids point in the direction of the hilus.
Conversely, the pith continues into the cortex in so-called pith rays.
The tips of the conical medullary pyramids are called renal papillae and each has a microscopic opening. These open into a small cavity, the kidney calyx.
The finished urine is collected in the goblets and passed on to the renal pelvis.
The pith and cortex 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 regulating blood pressure, and erythropoietin is important for the formation of red blood cells.
Connective tissue capsule and fat layer
Each kidney is covered by a tough capsule, a transparent covering of connective tissue. Around this is a thick layer of fatty tissue, which is surrounded by another thin layer of connective tissue.
The fat and connective tissue capsule protects the sensitive organ from impact injuries and anchors it to the posterior abdominal wall.
Nephron
Nephrons are the functional units of the kidney. Structure of these filter units You can find out more about the structure of nephrons in the article Nephron.
What is the function of the kidney?
You can read everything you need to know about renal function in the sub-text Kidney Function.
Where is the kidney located?
Both kidneys are located outside the abdominal cavity, in the so-called retroperitoneal space - i.e. behind the peritoneum (peritoneum). They are therefore not enclosed by the peritoneum.
Where exactly are the kidneys located?
They are located between the back wall of the peritoneum and the back muscles (psoas and quadratus lumborum muscles). The exact position depends on the breathing and the position of the body. The difference in height between the two organs caused by breathing is three centimeters.
The kidneys extend roughly from 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 lower than the left.
The right kidney is adjacent to the liver, duodenum, and the right bend of the large intestine (right colonic flexure). On the left there are neighborly relationships with the stomach and spleen, the tail of the pancreas (pancreatic tail), the descending part of the large intestine (descending colon), the splenic vein and splenic artery.
An adrenal gland (glandula suprarenalis) sits on each of the two upper organ poles. This is an important hormonal gland.
In front of and behind each kidney, there are densities of connective tissue, so-called fascia. They stretch from the diaphragm to the ridge of the intestine.
The architectural unit of kidney, fat capsule and fascia is often summarized under the term kidney bed.
What problems can the kidney cause?
Kidney diseases (renal diseases) manifest themselves through a variety of different symptoms. These result from the changes in the body that result from impaired organ function.
Possible complaints with renal diseases are, for example, dull back pain and colic-like back pain radiating towards the bladder. The urine may be red or cloudy and have an unpleasant smell. Foaming in the urine can also often be observed in renal diseases.
In addition, urine production can be reduced, so that patients pass very little or no urine at all (anuria). Swelling of the eyelids or ankles (edema) may also indicate renal disease.
In the further course of such a disease, additional symptoms may appear. These include, for example, loss of appetite, nausea, vomiting, general weakness, pale or grayish skin color, shortness of breath and water retention (especially in the legs). Itching of the skin, bad breath or a metallic taste in the mouth as well as a strong acidic body odor can also accompany a renal disease.
The main renal diseases are:
- Kidney stones (nephrolithiasis)
- Kidney (pelvic) inflammation (glomerulonephritis, pyelonephritis)
- Organ damage from drugs such as certain pain relievers
- Organ malformations
- Calcification of the renal arteries
- acute and chronic kidney 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 in the urine. Then the blood must necessarily be cleaned in another way to prevent life-threatening poisoning of the body:
One possibility is blood washing; The patient's blood is either filtered through a machine (hemodialysis) or his own peritoneum (peritoneum dialysis). The second option is to transplant a healthy kidney from an organ donor.
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