KIDNEY KNOWLEDGE SERIES - (1)

THE KIDNEYS

Q:     What are kidneys?

A:     The kidneys are two bean-shaped organs the size of a human fist. They are located on either side of the backbone, just below the ribcage and they work around the clock to keep the body healthy. The kidneys are a sophisticated filtering system. They pump up to 200 litres (20 buckets) of blood through around a million functioning units known as “nephrons”.

Q:     What are the roles of the kidneys?

A:     By filtering the blood this way the kidneys perform a range of vital functions including:

1.     Filtering waste from the blood

2.     Balancing the body’s fluid levels

3.     Helping to control blood pressure

4.     Helping to produce red blood cells

5.     Maintaining strong, healthy bones.

Q:     How do the kidneys filter waste from the blood?

A:    

·        The kidneys remove waste and excess fluids collected by the blood as they flow through the body.

·        Approximately 200 litres (20 buckets) of blood enter the kidneys each day via the renal arteries.  Here, its filters separate waste and excess fluid from the blood.

·        The majority of this waste enters the body in food and drink. The kidneys remove salt and other minerals leaving only what the body needs.

·        Once cleansed, the blood returns to the heart to be re-circulated through the body while the waste is stored in the bladder as urine.

·        When the bladder is full, the urine exits the body via the urethra. An adult passes an average of 2L of urine each day.

Q:     How do the kidneys balance the body’s fluid levels?

A:

·        By removing just the right amount of excess fluid, healthy kidneys maintain the body’s fluid balance.

·        Fluid content accounts for approximately 55 per cent of a woman’s total weight and 60 per cent of a man’s.

·        The kidneys maintain these proportions by balancing the amount of fluid that leaves the body as urine with the amount of fluid that enters (via liquid drinks and foods with a high fluid content).

Q:     How do the kidneys help to control blood pressure?

A:     High blood pressure, or hypertension, is common among those living with kidney failure. Healthy kidneys release hormones to help control blood pressure.

·        An important way is by regulating how much sodium (salt) and fluid the body keeps. If there is too much water in the body (fluid overload), a person’s blood pressure will rise. However if the body is lacking water (dehydration), a person’s blood pressure will drop. By monitoring and adjusting salt and water levels in the blood, the kidneys can correct imbalances and increase or decrease blood pressure when necessary.

Q:     How do the kidneys help to produce red blood cells?

A:

·        Healthy kidneys also produce the hormone “erythropoietin” (EPO), which is carried in the blood to the bone marrow where it stimulates the production of red blood cells.

·        Red blood cells carry oxygen throughout the body. A depletion of these cells puts one at risk of developing anaemia, a condition that makes you feel weak, cold, tired and short of breath.

Q:     How do the kidneys maintain strong, healthy bones?

A:

·        The kidneys help keep bones strong by activating “calcitriol” (vitamin D), which stimulates calcium and phosphate absorption in the blood and bones. The kidneys also monitor and adjust these levels when necessary.

·        Kidney failure may cause a drop in the production of calcitriol, leading to abnormal levels of phosphate and calcium, resulting in renal bone disease.