CKD and kidney function

Kidney functions affected by CKD

Water and electrolyte balance

The kidneys regulate water and electrolyte/mineral loss and thus balance the volume of water in the body. Excess electrolytes (for instance potassium, calcium and phosphate) and excess water are eliminated.

If less water is drunk, water and electrolytes can also be retained by decreasing urine production. Since over 75% of the body consists of water, and even a 2% reduction in body fluid is dangerous, it is clear how finely tuned the role of the kidneys is in regulating and maintaining fluid and electrolyte balance.

Regulation of blood pressure

The kidneys also influence blood pressure via control of water and electrolytes. The kidneys actively regulate this by producing a hormone known as renin.

Regulation of pH

The kidneys can eliminate both increased acids and bases, as required, and thus regulate the pH of the blood, which is essential for metabolic activity. Many enzymes are dependent on the pH of the blood to function correctly.

Production of hormonal substances

Erythropoietin is an essential hormone for regulating red blood cell (erythrocyte) production. Renin controls blood pressure. Calcitriol is the active form of vitamin D and regulates calcium and, thus, secondarily also phosphate levels in the blood. If there is too little calcium in the blood, calcitriol is released to reduce calcium excretion. In addition, if there is too little calcium in the blood, parathyroid hormone is released from the parathyroid glands, which liberates phosphate and calcium from the bone through bone resorption. Excess parathyroid hormone levels can lead to softening of the bones. Thus, the kidneys indirectly influence bone metabolism via regulation of calcium and phosphate excretion.

Removal of toxins

The kidneys continuously filter metabolic waste products and foreign substances (for instance drugs) from the blood and excrete them in the urine. Urinal substances of this kind include those that no longer have a function in the body and also toxins and toxic metabolic products, for instance from protein metabolism. These uraemic toxins can accumulate in the blood if less urine is passed and then directly damage the kidneys, blood vessels and impair bone metabolism.