WHAT ARE THE KIDNEYS? WHERE ARE THEY LOCATED?
The kidneys play key roles in body function, not only by filtering the blood and getting rid of waste products, but also by balancing the electrolyte levels in the body, controlling blood pressure, and stimulating the production of red blood cells.
The kidneys are located in the abdomen toward the back, normally one on each side of the spine. They get their blood supply through the renal arteries directly from the aorta and send blood back to the heart via the renal veins to the vena cava. (The term “renal” is derived from the Latin name for kidney.)
WHAT DO THE KIDNEYS DO?
When blood flows to the kidney, sensors within specialized kidney cells regulate how much water to excrete as urine, along with what concentration of electrolytes. For example, if a person is dehydrated from exercise or from an illness, the kidneys will hold onto as much water as possible and the urine becomes very concentrated. When adequate water is present in the body, the urine is much more dilute, and the urine becomes clear. This system is controlled by renin, a hormone produced in the kidney that is part of the fluid and blood pressure regulation systems of the body.
Kidneys are also the source of erythropoietin in the body, a hormone that stimulates the bone marrow to make red blood cells. Special cells in the kidney monitor the oxygen concentration in blood. If oxygen levels fall, erythropoietin levels rise and the body starts to manufacture more red blood cells.
Urine that is made by each kidney flows through the ureter, a tube that connects the kidney to the bladder. Urine is stored within the bladder, and when urination occurs, the bladder empties urine through a tube called the urethra.
WHAT CAUSES RENAL FAILURE?
Kidney failure may occur from an acute situation that injures the kidneys or from chronic diseases that gradually cause the kidneys to stop functioning.
In acute renal failure, kidney function is lost rapidly and can occur from a variety of insults to the body. Since most people have two kidneys, both kidneys must be damaged for complete kidney failure to occur. Fortunately, if only one kidney fails or is diseased it can be removed, and the remaining kidney may continue to have normal kidney (renal) function. If a both patient’s kidneys are injured or diseased, a donor kidney(s) may transplanted.
The list of causes of kidney failure is often categorized based on where the injury has occurred.
- Prerenal causes (pre=before + renal=kidney) causes are due to decreased blood supply to the kidney. Examples of prerenal causes of kidney failure are:
- Hypovolemia (low blood volume) due to blood loss
- Dehydration from loss of body fluid (for example, vomiting, diarrhea, sweating, fever)
- Poor intake of fluids
- Medication, for example, diuretics (“water pills”) may cause excessive water loss
- Abnormal blood flow to and from the kidney due to obstruction of the renal artery or vein.