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6.3. Kidney disease

Most frequent diseases of the urinary system

The main diseases of the urinary system are:

Kidney stones

The kidney stones or "kidney stones", are formed by precipitation of certain salts that were dissolved in the urine. They occur when the concentration in the urine is very high. When they leave the kidney and pass into the urinary tract, they produce the painful "nephritic colic".

If the size of the stones is small, they can be expelled through the urinary tract, but if it is larger, they can clog the ureters and cause renal colic. Then it is necessary to take medications to dissolve the stone or apply lasers or ultrasounds to break it down.

The nephrolithiasis is the disease that causes kidney stones when urine is very saturated salt of calcium or uric acid. You can prevent the formation of stones by drinking plenty of water so that the urine is more dilute.

It is a very common disease, affecting more than 10% of the population, more common in men and in people with a lot of exposure to heat, which makes them sweat a lot and lose water.


The cystitis is an infection of the urinary bladder that causes frequent desire to urinate, as well as itching and pain. Bacteria that make it to the bladder are eliminated during urination, but if not, they cause infection.

Cystitis is more common in women than in men, since they have a shorter urethra and closer to the anus. Older men, if they have an enlarged prostate that prevents them from urinating normally, are also at higher risk of suffering from it.


The nephritis is an inflammation of the kidney, which may have infectious origin or due to an autoimmune disease. Some of the symptoms are pain, blood in the urine, and fever.

Renal insufficiency

The kidney failure occurs when the kidneys are unable to filter enough blood in the glomeruli Malpighian, causing a smaller volume of urine and poor removal of waste substances.

It can be due to kidney damage, low blood pressure in the kidneys or urine is blocked in the urinary tract, which can affect chronically or acutely.

If the concentration of toxic substances is so high that it can endanger the life of the person, it is necessary to clean the blood by dialysis or, if necessary, transplant a kidney.


When the kidneys are not doing their job properly, dialysis (hemodialysisremoves waste substances from the blood and allows the patient to continue living.

In hemodialysis, a pump extracts the blood and passes it through a device that performs the functions of an artificial kidney, where the blood is in contact, through a semi-permeable, porous membrane, with a dialysate solution of a composition similar to that of of blood plasma. Small molecules will pass through this membrane, and water, urea, mineral salts, etc., which cannot be filtered by the kidney in a natural way, will be eliminated.

The duration of this treatment depends on the needs of each person, but it is usually about four hours, three times a week, since the blood has to pass through this filter several times, and a healthy kidney works 24 hours a day.

When the blood is clean, the blood returns to the patient's body through a vein.


Kidney transplant

If kidney failure is extreme, the best solution that allows the patient to have a quality life is kidney transplantation, which consists of placing a healthy kidney in the patient's body so that it fulfills the functions that the kidneys do not perform.

The transplanted kidney is placed in the lower abdomen, connected to the renal artery and renal vein. It will start to produce urine when blood flows through it.

One of the main problems in transplants is rejection, so transplant people must take immunosuppressive drugs so that their body does not detect the transplanted kidney as something foreign and tries to destroy it.

The donors of these kidneys can be deceased people, but they can also be living relatives, as long as they are compatible, since you can have a normal life with only one kidney.

Trasplante de un riñón

Basado en By BruceBlaus (Own work) [CC BY-SA 4.0], via Wikimedia Commons

Answer in your notebook

6.8.- Why do you think it is convenient for us to drink about 2 liters of water a day?


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