What are the major functions of the kidneys?

Kidneys are two essential organs in the human body’s metabolic process. They serve as a natural filter of the blood, and remove water soluble wastes, which are then diverted to the urinary bladder. In addition, kidneys also play an important role in eliminating excess acidity from the blood, as well as regulating blood pressure. They also produce hormones such as the one stimulating the production of blood cells in the bone marrow. Kidneys also have an influence on the production of vitamin D and the amount of calcium in the blood.

Kidneys come in pairs, each measuring around 11 cm long and weighting 160 g. It is possible to live normally with just one kidney, as one has more functioning renal tissue than is needed to survive. However, a large reduction of the amount of functioning kidney tissue will lead to chronic kidney disease, which is eventually fatal if not treated through dialysis or kidney transplantation.

What is kidney disease?

Kidney disease can have different causes. Kidneys can be damaged and lose long-term function due to inflammation in kidney tissue, high blood pressure (hypertension), diabetes or an excessive intake of certain medications. Various other causes exist, sometimes linked to genetic predispositions, such as polycystic kidney disease. Most kidney disease cases develop quietly and are not noticed for many years, not before a late stage of the illness. More rarely, cases can develop quickly (over days or weeks), with acute renal failure.

When the kidneys can no longer fulfil their duties, the functioning of the entire body is affected. The consequences for the organism vary depending on how the kidneys become defective. In most cases, too little of metabolic waste products are removed and these accumulate in the body. It also leads to imbalances in electrolytes and in the acid-base system. These changes can also lead to heart or digestive tract issues, or even abnormal changes in the nervous system. Most people show an increase in blood pressure because of a dysfunction of hormonal regulation and accumulation of water. In the advanced stages of the disease, decalcification of the bones may happen, as well as anaemia (due to the dysfunction of blood cell production) and the accumulation of water in the lungs and legs because of an insufficient removal of urine.


How is kidney disease treated?

If the kidneys’ performance decreases to less than 10-15% of the normal function, and they are left untreated over a long period, it will eventually lead to death. Therefore, when treating advanced renal failure, doctors must work on two main aspects: they have to prevent the life-threatening complications from the lack of kidney function while the long-term goal remains the full or nearly complete restoration of the patient’s health. However, severely damaged kidneys can only be treated through renal replacement therapy, which means replacing the organ’s vital functions with an appropriate treatment.

The best and most efficient form of renal replacement therapy is the successful transplantation of a healthy kidney. Although it is possible to receive a kidney from a living donor (since the donor can live normally with only one healthy kidney) as well as a deceased donor, there are not enough organs available worldwide. Moreover, sometimes transplantation may not be possible or desirable for medical reasons. In such cases, the only option is treatment with dialysis. There are various types of dialysis treatment, which all consist in filtering the patient’s blood, the most common being haemodialysis – using an artificial kidney – and peritoneal dialysis – using the peritoneal membrane as filter.

Read more about the main forms of renal replacement therapy.

Check out our infographic document for a brief overview of CKD and its consequences: