The kidneys, each about the size of a fist, play three major roles:
- removing waste products from the body, keeping toxins from building up in the bloodstream
- producing hormones that control other body functions, such as regulating blood pressure and producing red blood cells
- regulating the levels of minerals or electrolytes (e.g., sodium, calcium, and potassium) and fluid in the body
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 only one working kidney can live a normal life, since one kidney can do the work of two, but when both kidneys are no longer able to clear the body of waste, a person with kidney failure needs 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 damage 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. Some 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).
Symptoms and Complications
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 may 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:
- puffy eyes, hands, and feet (called edema)
- high blood pressure
- shortness of breath
- loss of appetite
- nausea and vomiting
- a bad taste in the mouth or bad breath
- weight loss
- generalized, persistent itchy skin
- muscle twitching or cramping
- a yellowish-brown tint to the skin
- urine that is cloudy or tea-coloured
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.
Making the Diagnosis
Unless the kidneys are swollen or there's a tumour, your doctor can't usually check for disease by feeling the kidneys. Instead, your doctor might test the urine and blood, take a scan of the kidneys, and test samples of kidney tissue. A routine urine test, called a urinalysis, checks for protein, sugar, blood, and ketones (created when the body breaks down fat). The urine is tested with a dipstick, which is a thin piece of plastic covered with chemicals that react when they touch substances in the urine. Your doctor will also check for red and white blood cells in the urine during a urinalysis (the urine is examined using a microscope). Depending on the suspected cause of the kidney problem, imaging tests such as an ultrasound, CT (computed tomography) or MRI (magnetic resonance imaging) may also be done.
Treatment and Prevention
Treatment of kidney disease depends on the type of disease, the underlying cause, and the duration of the disease.
When treating kidney disease, your doctor will try to treat the original cause. Kidney infections can be treated with antibiotics if the infection is caused by bacteria. Inflammation due to an immune reaction is more difficult to treat. However, your doctor will try and control the immune reaction with immunosuppressant medications such as corticosteroids. These work only in some types of nephritis (inflammation of the kidney). Some people have to eat less salt and protein until the kidney can remove these substances from the blood properly. Taking a diuretic medication (or "water pills") to make the body excrete more water and salt can also help control the swelling associated with kidney disease.
If your kidneys are not working correctly to eliminate waste, your levels of electrolytes (such as potassium or sodium) or minerals (such as calcium and phosphorus) in the body may be too high or too low. Your doctor may have you take medication to regulate these.
If someone has acute kidney failure, treating the underlying cause will often return kidney function to normal. In almost all cases of kidney failure, it is very important for high blood pressure to be treated aggressively to prevent further damage from occurring and to delay the progression of the disease.
You can potentially slow down or prevent the onset of kidney disease by regularly seeing your doctor to make sure your blood pressure, blood sugars, and cholesterol are under control. If you smoke, you should work with your doctor to quit.
Dialysis or transplantation treats end-stage kidney failure. In hemodialysis, blood is filtered through a tube that's inserted in the vein. The tube is connected to a machine that cleans the blood of wastes and the "clean blood" is returned to the body through another tube. Hemodialysis is usually performed in a hospital in three 4-hour sessions a week. In peritoneal dialysis, the space between the abdominal wall and organs is filled with a cleansing solution that absorbs toxins from the abdominal lining. The solution is then drained out into a bag. This procedure is done at home one to four times a day, seven days a week or overnight using a cycling machine.
In kidney transplantation, diseased kidneys are replaced with a healthy one. Kidney transplants usually work at least 80% of the time. The greatest danger is that the body might reject the transplant. To prevent this, transplant recipients are given powerful medications to suppress the immune system; these have the potential drawback of making one more susceptible to infections and to some types of cancer. The risks are usually worth it since the new kidney improves a person's chance for a normal and healthy life.
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