The Peculiarities of Kidney Function in Early Infancy

The peculiarities of kidney function in early infancy are as follows
1. Glomerular filtration rate is low and does not reach adult values until the child is between 1 and 2 years of age.
2. There is a large variation in the tubular length between nephrons, although glomerular size is less variable
3. The juxtaglomerular nephrons show more advanced development than cortical nephrons
4. The concentrating ability of the newborn kidney does not reach adult levels until about the third month of life.
5. Adequate amounts of antidiuretic hormone are secreted by the newborn pituitary gland, other factors appear to interfere with water reabsorption
6. The Henle's loop, essential to concentration ability, is incompletely developed in the newborn.
7. Urea synthesis and excretory burden is minimized.
8. The lower concentration of Urea, the principal end product of nitrogen metabolism, reduces concentrating capacity, since it also contributes to the concentration mechanism
9. Newborn infants are unable to excrete a water load at rates of older persons.
10. Hydrogen ion excretion is reduced
11. Acid secretion is lower for the first year of life
12. Plasma bicarbonate level is low.
13. As a result of these inadequacies of the kidney and less efficient blood buffers, the newborn is more liable to develop severe acidosis
14. Sodium excretion is reduced in the immediate newborn period, and the kidneys are less able to adapt to deficiencies and excesses of sodium
15. A isotonic saline infusion may produce edema because the ability to eliminate excess sodium is impaired. Conversely, inadequate reabsorption of sodium from tubules may compound sodium losses in disorders such as vmitting or diarrhea
16. Infants have a diminished capacity to reabsorb glucose and, during the first few days, to produce ammonium ions.

Quantitative age-depending characteristics of the kidneys and collecting system in children

1-3 days of Life
• Urine volume is 30-50 UV per 24 hour (ml)
• Frequency of Urination is 4-6 times/day
• Average volume of 1 urination is 5-10 ml
• Specific gravity of Urine is 1006-1012
• Glomerular filtration rate, according to creatinine clearance (endogenous) is 34-40 ml/min/1.73m2.

4-28 days of Life
• Urine volume is 200-300 UV per 24 hour (ml)
• Frequency of Urination is 20-25 times/day
• Average volume of 1 urination is 12-20 ml
• Specific gravity of Urine is 1002-1006
• Glomerular filtration rate, according to creatinine clearance (endogenous) is 40-50 ml/min/1.73m2

1-12 months of Life
• Urine volume is 600 UV per 24 hour (ml)
• Frequency of Urination is 10-25 times/day
• Average volume of 1 urination is 50-60 ml
• Specific gravity of Urine is 1004-1008
• Glomerular filtration rate, according to creatinine clearance (endogenous) is 60-70 ml/min/1.73m2

1-3 years of Life
• Urine volume is 700 UV per 24 hour (ml)
• Frequency of Urination is 8-10 times/day
• Average volume of 1 urination is 80-90 ml
• Specific gravity of Urine is 1009-1012
• Glomerular filtration rate, according to creatinine clearance (endogenous) is 70-100 ml/min/1.73m2

3-6 years of Life
• Urine volume is 800-1000 UV per 24 hour (ml)
• Frequency of Urination is 6-8 times/day
• Average volume of 1 urination is 90-100 ml
• Specific gravity of Urine is 1010-1016
• Glomerular filtration rate, according to creatinine clearance (endogenous) is 100-120 ml/min/1.73m2

6-10 years of Life
• Urine volume is 1100-1500 UV per 24 hour (ml)
• Frequency of Urination is 5-6 times/day
• Average volume of 1 urination is 100-150 ml
• Specific gravity of Urine is 1012-1020
• Glomerular filtration rate, according to creatinine clearance (endogenous) is 120-140 ml/min/1.73m2

Localization of kidneys according to vertebra column

Newborn
• The left side of the upper apex is on the level of the lower edge of XI thoracic vertebra
• The tight side of the upper apex is on the level of XII thoracic vertebra
• The left side of the lower apex is below the iliac crest.

3-5 months
• The left side of the upper apex is on the level of XII thoracic vertebra
• The right side of the upper apex is on the level of the lower edge of XII thoracic vertebra

1 year
• The left side of the upper apex is located on the level of the lower edge of XII thoracic vertebra
• The right side of the upper apex is located on the level of the lower edge of XII thoracic vertebra

2 years and older
• The left side of the upper apex is located like in Adult
• The right side of the upper apex is located like in Adult
• The left side of the lower apex is located above the iliac crest.

Any conspicuous deviation form any of these normal indexes indicate one thing- an abnormality!