Chronic kidney disease (CKD) is caused by progressive deterioration of kidney function due to loss of functional units in the kidneys. The functional units, called nephrons, consist of the glomerulus and tubules. The main site of filtration is called the glomerulus. It consists of an arteriole that winds around itself to form a spherical structure. The glomerulus is held together by the mesangial matrix, while the surface of the endothelial cells of the arteriole is covered by the foot processes of podocytes and the specialized glomerular basement membrane (GBM).
The GBM and the slit membranes of the interlocking foot processes of podocytes form the filtration barrier. After filtration, the filtrate enters the tubules (proximal tubules, loop of Henle, and distal tubules), where various molecules are reabsorbed or excreted into the urine; after this process, the urine enters the collecting ducts. During life, nephrons are lost due to injury and aging. Loss of nephrons is irreversible, but humans are born with a large reservoir of nephrons and a large proportion can be lost before symptoms appear. Because the kidney is the primary site for excretion of waste products, impaired kidney function has far-reaching effects throughout the body. For example, patients with CKD have a significantly increased risk of cardiovascular events.
How many people have CKD?
Large-scale, nationally representative screening programs conducted in Australia, Norway, and the United States in the 2000s have shown that more than 10% of the adult population has CKD. In the Western world, diabetes is the most common cause of CKD, followed by hypertension. With the increase in lifestyle diseases such as diabetes and hypertension and increased life expectancy, CKD is expected to become an increasing problem worldwide. In 2017, there were 697.5 million cases of CKD worldwide and about 1.2 million people died from CKD.
How is CKD treated?
If detected early, it is possible to halt or slow the progression of CKD pharmacologically. However, because of the reservoir of nephrons, CKD is usually not diagnosed until it is advanced. Patients who reach end-stage renal disease require dialysis or kidney transplantation. The main classes of treatment for CKD are medications to regulate blood pressure or treat the underlying causes of the disease (e.g. GLP-1 agonists and SGLT2 inhibitors for diabetes, which have a positive effect on kidney health).
How is CKD diagnosed?
Patients are diagnosed with CKD when the concentration of creatinine in the blood and/or protein or albumin in the urine is above a certain threshold. Because serum creatinine increases only after the loss of many nephrons and not all patients have proteinuria or albuminuria, better diagnostic tools are needed to identify patients at risk of developing CKD.
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