World Kidney Day
03.09
2017
World
Kidney
Day
Kidney Facts
Kidneys health >> Kidney through ages

Kidney through ages

 Our body is constantly changing, growing, adapting. Here are the main changes of our kidneys and urinary system by life period, as well as specific risk factors.

Infants

Infants

Children

Children

Adolescents

Adolescents

Adults : differences between gender

Adults : differences between gender

Pregnant women

Pregnant women

Elderly

Elderly
Infants

Infants

Kidneys of the fetus are formed during pregnancy. At this time, kidneys are developing and do not play their role of wastes elimination. Wastes are eliminated in the placenta and enter the mother’s blood circulation. They are then eliminated through the mother’s urinary system.

Babies are born with their adult number of nephrons (kidneys filtering units). However, these are not fully mature and their growth and maturation will continue during infancy.

Kidney function is thus immature in new born: the two main functions of the kidneys, which are body water regulation and wastes elimination, have not reach adult levels yet. Although it is adapted to their needs, it makes them more sensitive to some situations.

  • Babies’ kidneys cannot retain water as much as adults do. Babies are thus particularly sensitive to important water losses, like in case of diarrhea or hot temperature.
  • Infants’ kidneys capacity to concentrate urine is not mature. They are thus more sensitive to excessive salt intake. This explains why we are usually advised to use low mineral water with infant formulas.

Kidneys are mature by the age of 2 years. At this point, the kidneys have the same abilities as adults to filter the blood and to concentrate or dilute urine. They are able to ensure the same functions as adults.

Children

Children

Kidneys are fully mature by the age of 2 years. At this point, they are as able as adults to regulate body water and to ensure wastes elimination.

During childhood, the urinary system is still developing, and for instance, the bladder continues to grow. Children also learn how to control the voiding of their bladder around the age of 2 to 3 years. In parallel, they become more conscious of social norms. All these factors explain why as children grow up, they will need to go to the bathroom less often.

Adolescents

Adolescents

In teenagers, the growth of the urinary system is complete. Besides, by the age of 12, they are usually familiar with the sensation of an urge to urinate, with social norms, and are able to control the voiding of their bladder. As a result, their urinary function and micturition pattern are similar to adults.

However, young women and teenage girls are more at risk of Urinary Tract Infection. Girls aged between 15 and 29 years are the most affected by this infection: 1 out of 5 will develop a UTI.
In teenage boys though, UTI incidence remains low.

Did you know ?  
Some risk factors to develop an UTI in teenagers are the same as in adults.


Adults : differences between gender

Adults : differences between gender

There are only a few differences between men and women regarding kidney health. Here are the two main differences.

Kidney stones affect mainly men and are common in adults. Part of the explanation would be the differences in diet between men and women. As they usually eat in larger quantity, men often have more wastes to eliminate then women. This partly explains why men are advised to drink 2L of water per day, and women 1,6L per day. Also, men’s kidneys have an increased ability to concentrate urine compared to women. They are thus able to produce more concentrated urine, which is known to be a risk factor for kidney stones.

Women are more at risk of Urinary Tract Infections than men. This is mainly due to anatomic differences. Indeed, bacteria causing most of UTIs are called Escherichia coli, they are found in the rectum or the vagina. Now, women’s urethra is close to their vagina, as well as closer to the rectum and shorter than in men. As a result both the location and the length of women’s urethra make them more at risk of UTI then men.

Pregnant women

Pregnant women

Pregnancy is associated with changes in the urinary system. Pregnant women blood flow increases. As more blood is coming to the kidney filters, the kidneys adapt by increasing their filtration capacity (GFR). They globally grow in size, and the filtration surface increases without any change in the number of nephrons. Besides, late in pregnancy, the mother’s bladder might be twice as big as usual.

Pregnant women are more at risk of pyelonephritis (Urinary Tract Infection of the kidneys). Anatomical and physiological changes of the urinary system taking place during pregnancy tend to facilitate the progression of bacteria to the kidneys. Besides some symptoms similar to those of UTI are commonly encountered by pregnant women (higher frequency of urination, persistent urge to urinate, …) which complicates the detection of bladder infections. This partly explains why these infections reach the kidneys more often than in non-pregnant women.

Did you know ?  
A pregnant woman needs more water: as the baby grows, her body has to respond to increasing needs for resources, such as water. Woman’s body usually gains 6 to 8L of water during pregnancy. The European Food Safety Association (EFSA) also recommends that pregnant women increase their water intake up to 1,8L of water per day as of the second trimester.


Elderly

Elderly

With aging, kidney mass and kidney function reduce. In parallel to their decrease in mass (up to 20%), elderly’s kidneys also become less capable of regulating water balance. In some situations, like in case of diarrhea or hot temperature, elderly have a reduced capacity to conserve body water. They are thus more sensitive to some situations that can put them at risk of dehydration.

Urinary Tract Infections are quite common in elderly and usually follow a catheterization, during a hospitalization for example. To prevent UTI, doctors often advise to increase fluid intake, to keep a good hygiene and a healthy lifestyle.

Elderly are more affected by Chronic Kidney Disease (CKD). Being 60 years or older is generally considered as a risk factor to develop CKD.

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