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 electrolytesElectrolytes are substances that produce an electrically conducting solution when dissolved in water, releasing mineral ions such as sodium, potassium, chloride and calcium. These ions can either be the positively or negatively charged or, combined as a salt, neutral.... (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 reninA hormone-like enzyme, generated and stored in the kidneys. If blood pressure drops, it is released from the kidneys and is highly efficient in raising blood pressure.....
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
ErythropoietinErythropoietin, abbreviated to EPO, is a growth factor that stimulates red blood cell production. EPO can be produced biotechnologically and administered for kidney failure or after chemotherapy.... is an essential hormone for regulating red blood cell (erythrocyte) production. Renin controls blood pressure. CalcitriolCalcitriol is the active form of vitamin D3. It is synthesised in the kidney from vitamin D. It is independently activated by three factors: increased parathyroid hormone levels, reduced calcium levels or indirectly via reduced phosphate levels. Calcitriol acts on four organs: 1) Bones: It... 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 hormoneParathyroid hormone (PTH) is a hormone secreted by the parathyroid glands, which regulates calcium levels in the blood. PTH is secreted in response to low blood calcium levels (hypocalcaemia). An increase in calcium concentration above the normal value inhibits PTH production (negative feedback). PTH stimulates... is released from the parathyroid glands, which liberates phosphate and calcium from the bone through bone resorptionThe re-uptake of substances from tissues, in particular bone, into the blood. It should not be confused with absorption, the initial uptake of substances into the body, for instance from food in the intestines, through the lungs and via the skin. Reabsorption, in contrast, occurs.... 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 toxinsToxic, nitrogen-containing urinary substances responsible for uraemia and kidney damage.... can accumulate in the blood if less urine is passed and then directly damage the kidneys, blood vessels and impair bone metabolism.