After undergoing a health check-up, the doctor says that you have chronic kidney disease, which often causes a lot of anxiety among the elderly. They are worried whether they will need to undergo dialysis or not, concerned about what caused it, wondering what to do next, if their kidney function will return to normal or not, what medications to take, and if they must take medications to clean the kidneys. Therefore, it is essential to understand the changes in kidney function as one enters old age.
Understanding Kidney Values
First, it is important to understand what “kidney values” are. When doctors report blood test results, you often hear the term creatinine, which is the “kidney value” doctors refer to. High creatinine levels indicate deteriorating kidney function. Currently, there are more reliable and precise calculations of kidney function, such as calculating the “GFR” value, which also depends on the creatinine levels, and a decrease in GFR indicates declining kidney function.
Changes in the Kidneys
As age increases, both the structure and overall function of the kidneys change. The kidneys become smaller in size, and their weight and volume decrease. Compared to young people, a normal kidney weighs about 245 – 290 grams, but by the age of 90, the kidney’s weight can decrease by 15 – 20%, leaving it at only about 180 – 200 grams. Microstructural changes also occur; the ability of the kidney units to filter waste and water and retain proteins in the bloodstream decreases because the components of the kidney units and blood vessels overall tend to deteriorate with age. Fibrosis begins to accumulate in the kidney units. The body releases certain substances, including free radicals and inflammatory agents, which have the potential to damage the kidney structure. These changes are normal with aging. However, if the elderly have chronic conditions such as high blood pressure, diabetes, or insulin resistance, stress, etc., or consume a diet too high in protein, carbohydrates, or fats that the body cannot fully metabolize, it will accelerate these changes.
An important note is that in the elderly, when kidney disease or injury occurs, the recovery to normal condition is relatively slow compared to that of younger kidneys. It has been reported that the progression of kidney deterioration promotes a higher incidence of cardiovascular diseases.
Meanwhile, studies have identified factors that can help maintain kidney health and slow down the deterioration, such as certain blood pressure medications, Vitamin D, Vitamin E, and some genes, which may help slow the disease progression. Still, ultimately, it is up to the doctor to decide what is appropriate for each elderly individual. Besides medication, it is found that limiting daily caloric intake by about 25 – 45%, while keeping essential minerals, amino acids, and vitamins the same, and avoiding high-fat foods can help slow down the development of kidney disease, heart disease, and vascular diseases.
The changes in kidney function with aging show that every 10 years of age, the blood supply to the kidneys reduces by 10%, leading to a decrease in kidney function or GFR, and these changes occur more in men than women. Additionally, the response to hormones and neurotransmitters affecting the kidneys also decreases.
In the elderly, blood vessels supplying the kidneys have a reduced ability to expand compared to younger people, but the rate of blood vessel contraction supplying the kidneys is roughly the same between the two groups. Overall, in the elderly, the blood supply to the kidneys decreases, which, combined with structural changes in the kidneys, further promotes the progression towards chronic kidney disease.
There are also changes in the balance of minerals in the body. The ability of the kidneys to absorb or excrete sodium decreases, as does the ability to expel acids from the body. Combined with consuming too much protein, this can lead to an increased acidic condition of the blood. If this acidic condition persists chronically, it will lead to the breakdown of calcium and bicarbonate from the bones, reducing calcium absorption in the kidneys and leading to osteoporosis.
In terms of potassium balance in the elderly, overall body potassium generally decreases because elderly people have less muscle mass than younger people. However, blood potassium levels tend to increase because the blood supply to the kidneys decreases with age, reducing potassium excretion and the production of hormones that help reabsorb potassium.
As for calcium balance, the rate of calcium reabsorption and expulsion through the kidneys between young and old is roughly the same. However, in the elderly, the reabsorption of calcium in the intestines is much less than in younger people, and there is an increased production of parathyroid hormone, which is used to release calcium from the bones into the bloodstream. This response to the hormone is quicker in the elderly, thus promoting osteoporosis more easily than normal.
Regarding vitamin D, even though the vitamin D produced by the kidneys decreases, overall blood levels of vitamin D between the two age groups are roughly the same. Additionally, in the elderly, the ability of the kidneys and intestines to reabsorb phosphate decreases, thus there is a greater chance of developing low blood phosphorus.
In summary, the characteristic changes in the kidneys with aging are quite diverse. Today, with longer life expectancy, people live with kidney deterioration for longer. If the deterioration is not slowed down, they may face end-stage kidney disease, which ultimately requires dialysis.
