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The kidney (ren, Greek nephros) is a paired excretory organ that forms and removes urine. Kidney bean-shaped, dark red, dense consistency. The size of the kidney in an adult is as follows: length 10-12 cm, width 5-6 cm, thickness 4 cm. Kidney mass varies from 120 to 200 g. The kidney surface in an adult is smooth. There are a more convex front surface (facies anterior) and a less convex posterior surface (facies posterior), an upper extremity (extremitas superior), and a convex lateral margin (margo lateralis) and a concave medial margin (margo medialis). In the middle section of the medial edge there is a depression - the renal gates (hilum renalis). The renal artery includes the renal artery and nerves, the ureter, renal vein, and lymphatic vessels exit from them. Blood vessels and nerves form a so-called renal pedicle. The renal gates pass into a vast depression that extends into the kidney substance and is called the sinus renalis. In the renal pancreas are small and large renal cups, renal pelvis, blood and lymph vessels, nerves and fatty tissue.
The renal parenchyma consists of two distinctly different layers: the outer and the inner. The outer layer, the cortex of the kidney (cortex renalis), or the kidney cortex, is abundantly blood-flowing, as a result of which it has an intense red color. Cortical matter occupies the entire peripheral (external) part of the organ; its thickness is 1 cm. The inner layer, known as the medulla renalis, is significantly inferior to the cortex in terms of blood flow intensity. Structurally the brain substance is devoid of homogeneity. It is divided into 8-18 conical structures, which are known as pyramides renales, located fan-shaped: their base faces the kidney cortex, and the tip (renal papilla renalis) is located in the area of the renal gates (hilum renale). Each of the pyramids is separated from the other by the renal columns (columnae renales), which are parts of the cortical substance of the kidney that are implanted in the brain substance.
The kidney pyramid and part of the cortical substance above it is called the kidney lobe. In the brain substance, two zones are distinguished: the outer and the inner. The area of the outer zone of the medulla that borders the cortical substance of the kidney is called the corticomedullar compound. From it to the cortex of the kidneys are the so-called brain rays (radii medullares), which are the functional structures of the cortex - the direct segments of the proximal tubules, the thick ascending segments and the cortical collecting tubes. The inner zone (zona interna) of the medulla ends with the region of the renal papilla, free from the structural elements of the nephron. Papillae permeated with 10-25 small holes, which are the terminal segments of the renal collecting tubes (Bellini's ducts). The mouth of these ducts is located around the tip of the papilla.
The renal papillae open into small calyce minerals (calices renales minores) - the first structural elements of the urinary tract, connecting the kidney parenchyma with the urinary system, which is represented by the ureters, bladder and urethra.
Topography of the kidneys
The kidneys are located in the lumbar region (regio lumbalis) on either side of the vertebral column, on the inner surface of the posterior abdominal wall and lie retroperitoneally (retroperitoneally). The upper ends of the kidneys are approximated to each other up to 8 cm, and the lower ends are separated from each other by II cm. The longitudinal axis of the right and left kidneys intersect at the top at an angle open downward. The left kidney is slightly higher than the right kidney, which lies directly under the liver. The upper end of the left kidney is at the level of the middle of the XI thoracic vertebra, and the upper end of the right kidney corresponds to the lower edge of this vertebra. The lower end of the left kidney lies at the level of the upper edge III of the lumbar vertebra, and the lower end of the right kidney is at the level of its middle. In relation to the ribs, the kidneys are arranged as follows: the XII rib crosses the posterior surface of the left kidney almost at the middle of its length, and the right one roughly at the border of its upper and middle thirds. There are individual features of the topography of the kidneys. Their high and low location is different. In 11% of women, the lower end of both kidneys touches the crest of the iliac bones.
The kidneys are in complicated relationships with neighboring organs. The posterior surface of the kidney, along with its membranes, is attached to the lumbar part of the diaphragm, the square muscle of the waist, the transverse abdominal muscle and the large lumbar muscle, which form a kidney for the kidney . The upper end of the kidney is in contact with the adrenal gland. The anterior surface of the kidneys on the larger length is covered with a leaf of the parietal peritoneum and comes into contact with some internal organs. To the upper two thirds of the anterior surface of the right kidney is the liver, and to the lower third - the right bend of the colon. The medial margin of the right kidney is the descending part of the duodenum. The anterior surface of the left kidney in the upper third touches the stomach, in the middle - with the pancreas, and in the lower - with the loops of the jejunum. The lateral margin of the left kidney is due to the spleen and left curvature of the colon. The normal topographic location of the kidneys is provided by its fixation apparatus, which includes the kidney bed, the "renal pedicle", the kidney shell (especially the renal fascia).
Of great importance is intra-abdominal pressure, supported by contraction of the abdominal muscles.
In the kidney, several membranes are isolated. Outside, the kidney is covered with a thin connective tissue plate with a fibrous capsule (capsula fibrosa), which can be easily separated from the kidney substance. Outside the fibrous capsule is a significant thickness of the fat capsule (capsula adiposa), which penetrates through the renal gates into the renal sinus. The fat capsule is most pronounced on the posterior surface of the kidney, where a peculiar fat pad is formed - the perineal fat body (corpus adiposum pararenale). With a rapid reduction in the thickness of the fat capsule (with rapid weight loss), the kidney can become mobile (a wandering kidney).
Outside the fatty capsule, the kidney is covered (in the form of an open bottom of the sac) by the fascia renalis, consisting of two sheets - the preference and the back-bone fascia. The preference sheet covers the front of the left kidney, kidney vessels, the abdominal part of the aorta, the lower vena cava and extends in front of the spine to the right kidney. The posterior- kidney fascia of the renal fascia on the left and right is attached to the lateral sections of the vertebral column. The lower edge of the pre- and posterolateral leaf of the renal fascia is not joined together. Renal fascia by means of strands of fibrous connective tissue that permeate the fatty capsule is connected to the fibrous capsule of the kidney. Ahead of the preference sheet of the renal fascia is the parietal leaflet of the peritoneum.
Renal X-ray of the kidney
On the roentgenogram, the contours of the kidney are smooth, have the appearance of arcuate lines; the shadow of the kidneys is uniform. The upper border of the shadow of the left kidney reaches the XI rib and the middle of the body XI of the thoracic vertebra, and the right - the lower edge of the same vertebra. The shape and magnitude of the kidney are detected by introducing oxygen or gas into the retroperitoneal space - pneumoreteroperitoneum. When pyelography (after the introduction of contrast agent into the blood or retrograde through the ureter), the shadow of the renal pelvis is at the level of the bodies of I and II lumbar vertebrae, the shadows of the kidney cups are visible. The condition of the arterial bed of the kidney is revealed through arteriography.