Age features of the kidney

In newborns and infants, the kidney is rounded, its surface is tuberous due to its lobed structure, which is associated with inadequate development of cortical substance at this age. The lobate structure of the kidney is preserved up to 2-3 years. The length of the kidney in the newborn is 4.2 cm, and the mass is 12 g. At infancy, the kidney size increases about 1.5 times, and the mass reaches 37 g.

During the first childhood, the length of the kidney is equal to an average of 7.9 cm, weight - 56 g. In adolescents, the length of the kidney reaches 10.7 cm and the mass of the kidney is 120 g.

In newborns, the thickness of the cortical substance of the kidney is approximately 2 mm, and of the brain - 8 mm; their ratio is 1: 4. The thickness of cortex in an adult compared to that of a newborn increases approximately 4-fold, the cerebral-only 2-fold.

The growth of kidneys occurs mainly in the first year of life of the child. In the period from 5-9 years and especially in 16-19 years, the size of the kidney increases due to the development of the cortex, which lasts until the end of the puberty period; the growth of the brain substance stops by 12 years. The mass of the cortical substance of the kidneys increases due to the growth in length and width of the proximal and distal convoluted tubules and the ascending part of the nephron loop. The renal pelvis of the newborn is broad, ampoule.

The fibrous capsule of the kidney becomes well visible in the fifth year of the child's life, and by 10-14 years in its structure it is close to the fibrous capsule of an adult. The leaves of the renal fascia in the newborn are very thin, thicken gradually as the child's age increases. The fat capsule is almost absent and begins to form only to the period of the first childhood, in the future it gradually thickens. By 40-50 years, the thickness of the fatty capsule of the kidney reaches its maximum values, and in the elderly and senile age it becomes thinner, sometimes disappears.

The topography of the kidneys changes with age due to their descent. In the newborn, the upper end of the kidney is projected at the level of the upper edge of the XII thoracic vertebra, and in infancy (up to 1 year) - already at the mid-body level of the XII thoracic vertebra. The lower end of the kidney at the newborn is at the level of the lower edge of the IV lumbar vertebra, in the one-year-old child - by 1/2 vertebra above, which is associated with the rapid growth of the spinal column. After 5-7 years, the position of the kidney relative to the spine approaches that of the adult.

At the age of over 50, especially in old and malnourished people, the kidneys may be located lower than at a young age. During all periods of a person's life, the right kidney is located somewhat lower than the left one.

In a newborn, both the kidneys in the region of the upper end and the anterior medial surface (almost to the kidneys) touch the corresponding adrenal gland. The liver, the caecum and the appendix are also attached to the right kidney. The left kidney is on a small part of the spleen; the medial of the gate is the tail of the pancreas.

The longitudinal axis of each kidney in children up to 3-4 years passes parallel to the spine, the renal gates are facing somewhat anteriorly. By 5-6 years, the longitudinal axes take an oblique (converging upward) direction.

As the human body grows, the position of the kidney and the relative length of its arteries and veins that make up the "renal pedicle" change. The newborn "renal leg" is relatively long, the vessels are obliquely positioned: the beginning of the renal artery and the mouth of its vein are above the kidney gates. Then the "renal leg" gradually assumes a horizontal position, and after 50 years due to some displacement of the kidneys down the length of the "renal pedicle" increases and it is directed downwards.

[1], [2], [3], [4], [5], [6]