What is Chronic Kidney Disease (CKD)
Chronic kidney disease (CKD) is a condition that causes gradual damage to the kidneys over time, greatly reducing their ability to function.
As the disease progresses, medical treatment may be required to perform the functions of the kidney. These options include dialysis, or as a last resort, kidney transplant. It is estimated that CKD affects around 14 percent of the general population in the US. Globally, CKD is recognized as a growing epidemic that has a major impact on an individual’s ability to maintain a regular schedule and social life. Additionally, prevention and careful management of CKD can prevent the onset of other related conditions, such as heart disease.
The Kidneys: structure and function
The kidneys are two bean-shaped organs that are about 12 centimetres in length and located the back of the abdomen on either side of the spine.
Each kidney is made up of around a million small functional units called nephrons. Each nephron is subdivided into two parts: The renal glomerulus, which is in charge of filtering the blood, and the renal tubule, which puts important substances back into the blood and excretes waste in the urine.
The kidneys perform purification of blood constantly. They also regulate the body's fluid balance, control levels of electrolytes (sodium, potassium, chlorine, bicarbonate, phosphorus, calcium), glucose, amino acids, uric acid, and urea.
They help to control blood pH by absorbing and/or excreting bicarbonate.
Additionally, they control the volume of fluids in the body by conserving or removing water. They perform this function by secreting hormones that are essential for a number of vital functions in the body.
The parameters used to assess kidney health are:
- azotemia, which is increased concentration of nitrogen in the blood
- creatinemia, which is increased concentration of creatinine in the blood
- creatinine clearance, which is a measure of how much creatinine is removed from the blood per minute
By measuring the amount of creatinine, we can also obtain the glomerular filtration rate (GFR), which gives an indication of how efficiently the kidneys are in purifying the blood over a period of time.
What are the causes of CKD?
CKD can be caused by a series of diseases that affect kidney function.
The most common are hypertension and diabetes mellitus, but can also include pyelonephritis, glomerulonephritis, polycystic kidney disease or other congenital or genetic kidney diseases, and chronic obstruction of the urinary tract.
There are also risk factors that increase the likelihood of developing the disease, such as obesity, high cholesterol levels, and urinary tract infections.
What are the stages of CKD?
The stages of CKD are defined using a model based on glomerular filtration rate (GFR)
GFR is measured in ml per minute. This measurement is obtained by evaluating the volume of plasma “cleared” of a given substance (in this case, creatinine) in a given amount of time by the kidney. GFR slows as kidney function declines.
See the reference values in the diagram:
Stage 5 is defined as the uremic or end stage, signifying almost complete loss of kidney function. Once this stage is reached, the nephrologist decides, depending on the clinical picture, the best form of treatment, especially with regard to preparation for renal replacement therapy (dialysis or kidney transplant).