How does the kidney function?
What causes chronic kidney failure?
What is chronic kidney failure?
What are the potential repercussions of chronic kidney failure?

How does the kidney function?
The kidneys play an important role in maintaining the body's water, electrolyte and acid-base balance, discharging metabolic end products and toxins. Both kidneys are situated in the retroperitoneal space. Each receives blood via a large artery (arteria renalis) and a large vein (vena renalis). At the microscopic level, a kidney consists of nephrons each of which comprises a glomerulus and a tubular system. Every glomerulus is made up of a capillary tuft, an efferent artery and an enclosing capsule named Bowman capsule. Located between the Bowman capsule and the glomerulus is a space into which the primary urine from the capillaries is pressed out by the blood pressure (glomerular filtration). The composition of primary urine is similar to plasma water. It contains all substances capable of passing through the glomerular filter (< approximately 60 kDaA).
Substances are resorbed or secreted the primary urine as it travels through the tubular system in a selective process, which determines the substances which the body is to recover or discharge; body water is recovered in quantities that ensure a beneficial water balance for the body. At the end of the tubular system, the final urine reaches the pelvis of the ureter (pelvis renalis) from where it is discharged via the ureter and bladder. Besides serving to discharge uremic toxins, kidneys also play a vital role in regulating electrolyte (potassium, sodium, calcium, etc.), acid-base (bicarbonate, H+ ions), and water metabolism. In combination with other metabolic functions, these kidney functions ultimately also serve to regulate blood pressure. Furthermore, kidneys are responsible for producing and activating important hormones like erythropoietin for hematosis and vitamin D for bone metabolism (endocrine function).

What causes chronic kidney failure?
Chronic kidney failure can have a variety of causes differing in terms of location. Causes can be prerenal e.g. circulatory shock, intrarenal e.g. inflammation, diabetes, high blood pressure, or postrenal e.g. blockage of urinary channels through kidney stones. Common causes of chronic renal insufficiency are diabetes mellitus, glomerulonephritis and hypertension.
 
What is chronic kidney failure?
Chronic kidney failure is a slow, progressive loss in renal functions over a period of several months or years until the final phase of a chronic kidney disease. It is characterized by a residual renal capacity of just 15% or less, and notably impaired or even entirely absent urine discharge. Chronic kidney failure typically occurs in 4 phases:

1. Impaired kidney function. There are hardly any clinical symptoms, since residual renal functions are still just sufficient.

2. Minor renal insufficiency. Substances requiring renal discharge are present in higher levels; creatinine in quantities of up to 3 mg/dl (normal value < 1.1 mg/dl). Renal functions are borderline.

3. Renal insufficiency. Creatinine levels are 3-10 mg/dl. Renal functions are severely impaired and clinical symptoms are emerging distinctly.

4. Terminal renal insufficiency (final stage). Creatinine levels are > 10 mg/dl. Renal functions are no longer adequate and the patient exhibits uremic syndrome, including oedema, acidosis , and hypertension. Only a kidney transplant or renal replacement therapy (dialysis) will now help.
 
What are the potential repercussions of chronic kidney failure?
Chronic kidney failure can have diverse repercussions. Different symptoms can occur depending on which renal functions are impaired. All consequential symptoms are categorized under uremic syndrome. Potential complications include oedemas in the extremities and organs, possibly leading to hypertension. The patient is no longer able to properly discharge uremic toxins, and additionally suffers imbalances in acid-base, sodium, potassium, calcium, phosphate and vitamin D levels. Many patients ultimately develop anaemia. Because chronic renal insufficiency is often irreversible, the patient either requires a kidney transplant or life-long dialysis therapy.