The kidneys, each about the size of a fist, play three major roles:
After the blood has circulated through the body, it passes into the kidneys. The kidneys filter waste products and excess salt and water out of the blood, and pass these out of the body as urine. The kidneys also make hormones that control blood pressure, as well as maintain bone metabolism and the production of red blood cells. It's a serious problem when the kidneys stop working. Waste products that build up in the body cause imbalances in chemicals needed to keep the body functioning smoothly.
There are many different types of kidney diseases. Kidney diseases can lead to end-stage renal disease (ESRD), a condition in which the kidneys fail to work normally. People with kidney failure need to receive dialysis or a kidney transplant.
The most common causes of kidney disease include diabetes, high blood pressure, and hardening of the arteries (which damages the blood vessels in the kidney). Some kidney diseases are caused by an inflammation of the kidneys, called nephritis. This may be due to an infection or to an autoimmune reaction where the body's immune or defence system attacks and damages the kidneys. Other kidney diseases, such as polycystic kidney disease are caused by problems with the shape or size of the kidneys (anatomic disorders), while other kidney diseases interfere with the inner workings of the kidneys (metabolic disorders). Most metabolic kidney disorders are rare, since they need to be inherited from both parents.
Other common causes of kidney failure include certain medications that can be toxic to kidney tissue, and blockages of the system that drains the kidneys (which can occur with prostate problems).
The symptoms of kidney disease depend on the type of disease that a person has. If the disease is caused by a bacterial infection, the person will develop a high fever. Other signs of kidney disease include passing too much or too little urine, or passing blood or abnormal levels of chemicals in the urine. Nephrogenic diabetes insipidus is a kidney disease in which the kidneys cannot remove enough water from the urine to make it concentrated.
Mild to moderate kidney disease often does not have any symptoms. However, in ERSD or uremia, when the toxins accumulate in a person's blood, symptoms may include:
Kidney disease usually does not cause pain, but in some cases pain may occur. A kidney stone in the ureter (a tube leading from the kidney to the bladder) can cause severe cramping pain that spreads from the lower back into the groin. The pain disappears once the stone has moved through the ureter.
Kidney disease can lead to both acute and chronic kidney failure, both of which can be life-threatening. Acute kidney failure happens suddenly within hours to days, whereas chronic kidney failure happens gradually over a period of months to years. Acute kidney failure can often be reversed if the underlying disease is treated. In both conditions, the kidneys shut down and can no longer filter wastes or excess water out of the blood. As a result, poisons start to build up in the blood and cause various complications that can affect various body systems. Chronic kidney failure eventually reaches an end stage. This condition occurs when the kidney is working at less than 10% of full capacity. At this stage, the person will need dialysis or a kidney transplant to be able to go on living.