Kidneys are two organs in the abdomen of vertebrates that are shaped like beans. They make urine (the yellow waste water that comes out of the urethra.) They are part of the urinary system. When medical professionals discuss the kidneys, they typically refer to the word renal. For example, renal failure is when the kidneys are sick and do not work.
Erythropoetin is made by the kidneys if there is less oxygen in the kidney. Erythropoetin tells the bone marrow to make more red blood cells. Red blood cells carry oxygen in the blood. So this means there will be more oxygen carried in the blood.
Renin is made by the kidney if there is low blood pressure, low volume of blood, or too low salts in the blood. Renin tells the blood vessels to be smaller. It tells the adrenal gland to make aldosterone (which tells the kidneys to save salts). It tells the body to drink more water. All of this makes the blood pressure go up.
The kidney's most important work is keeping homeostasis. Homeostasis means that the body keeps a stable environment inside itself. The body wants to have the consistent and proper amount of water, salt, and acid in the blood. This makes the body work better. The kidney keeps these things constant.
If there is too much water, the kidney puts more water in the urine. If there is not enough water, the kidney puts less water in the urine. This is why people make less urine when they are dehydrated (have not enough water in the body and are thirsty).
There are many types of kidney diseases. If kidney disease makes the kidneys not able to do but they do work in part. People can have mild renal failure and have no symptoms. As long as it does not become worse, people may not even know they have it. Severe renal failure means very bad failure. The kidneys do not work very much at all. People with severe renal failure always have symptoms. They may need special care from doctors
The main kinds of kidney diseases are:
- Kidney stones – this is when a solid substance forms in the urine. This stone moves through the urinary system until it cannot go more, because it is too big to go through. Then it stops the urine flow. This usually causes very bad pains. After a time, the stone usually goes out or passes. If it does not go out, doctors may have to help it.
- Kidney infections – also called pyelonephritis. This is when a bacteria grows in the kidney. Symptoms are back pain, vomiting, fever, and dark or bloody urine. People with pyelonephritis need strong antibiotic medicines to kill the bacteria.
- Glomerulonephritis – this is a disease of the small things in the kidney that make the urine. These are called glomeruli. Glomerulonephritis is an autoimmune disease. It makes it so that the kidneys do not work well. It can cause mild or severe renal failure.
- Congenital kidney disease – this is when people are born with kidneys that do not work right. Sometimes people are born with kidneys that are in the wrong place, or do not have the right shape. About 1% of people are born with only one kidney.
- Polycystic kidney disease - this is an inherited disorder in which cysts grow in the kidneys, and destroy the kidney tissue until the kidneys can no longer perform their functions.
- Diabetic nephropathy – this is the disease diabetics get when their blood sugar is very high for a long time. This is one of the most common causes of kidney failure in the United States
- Hypertensive nephropathy – this is the disease people with hypertension (high blood pressure) get when their blood pressure is high for a long time. Many people have hypertensive and diabetic nephropathy together.
- Cancer – Renal cell carcinoma is the most common kind of kidney cancer. It is most often in adults. It is a very bad cancer. It is hard to stop it with radiation treatments or chemotherapy.
People who do not have good kidneys are very sick. If they have severe renal failure, they cannot live unless they have a replacement for their kidneys. Replacement is something that takes the place of something else.
There are two ways to replace the kidneys: dialysis and transplantation
Dialysis is when doctors use a machine and medicines to do the work that kidneys do. There are two kinds of dialysis: hemodialysis and peritoneal dialysis.
Peritoneal dialysis is when doctors put a plastic tube into the persons abdomen. Every day the person fills the abdomen with fluid. The extra salts, waste, and water that the body does not need goes into the fluid. Then the fluid comes out and takes the wastes with it. This does part of the job that kidneys do.
Hemodialysis is when doctors take blood from a person, clean the blood with a special kind of filter, called haemodialyser, managed through a special machine, and put it back in the person. When the blood is cleaned, water, salts, and wastes are taken out of it. This must be done 2-4 times every week (usually 3 times.) It takes 2-4 hours to do this each time.
Hemodialysis and peritoneal dialysis are not perfect. They do some of the work of the kidney, but it is not as good as a real kidney. So people who need dialysis are not as healthy. They must take medicines also. For example, in kidney failure, the kidneys do not make erythropoetin. So doctors have to give people erythropoetin so they make enough red blood cells.
A better way to do the kidneys' work is to give the person another kidney. This is called a renal transplant. Kidney transplants are the most common organ transplant that happens. It is more common because we have two kidneys, but only need one kidney to live. People who are alive can donate a kidney to another person. With other organs, the donor must be dead first.
Even transplants are not the same as kidneys people were born with. A person who gets a renal transplant must take strong medicines to stop their body from attacking the new kidney. Sometimes, after years, the transplanted kidney stops working. But sometimes a patient can get a new transplanted kidney after the first one stops working.
It was widely believed in Europe that the conscience was actually located in the kidneys. This idea was taken from the Hebrew Bible. In modern times, medical scientists have shown kidneys do not have this kind of psychological role.
|Urinary system (edit)|
|Kidneys | Ureters | Urinary bladder | Urethral sphincters | Urethra|