Kidneys

What are the kidneys?

The kidneys play key roles in body function, not only by filtering the blood and getting rid of waste products, but also by balancing levels of 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.)

When blood flows to the kidney, sensors within the kidney decide 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.

After the kidneys filter blood, the urine is excreted through the ureter, a thin tube that connects it to the bladder. It is then stored in the bladder awaiting urination, when the bladder sends the urine out of the body through the urethra.

 

What causes kidney failure?

Kidney failure can occur from an acute situation or from chronic problems.

In acute renal failure, kidney function is lost rapidly and can occur from a variety of insults to the body. The list of causes 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; and
• abnormal blood flow to and from the kidney due to obstruction of the renal artery or vein.

Renal causes of kidney failure (damage directly to the kidney itself) include:

• Sepsis: The body's immune system is overwhelmed from infection and causes inflammation and shutdown of the kidneys. This usually does not occur with urinary tract infections.
• Medications: Some medications are toxic to the kidney, including nonsteroidal anti-inflammatory drugs like ibuprofen and naproxen.
• Post renal causes of kidney failure (post=after + renal= kidney) are due to factors that affect outflow of the urine:

• Obstruction of the bladder or the ureters can cause back pressure because the kidneys continue to produce urine, but the obstruction acts like a dam, and urine backs up into the kidneys. When the pressure increases high enough, the kidneys are damaged and shut down.
• Prostatic hypertrophy or prostate cancer may block the urethra and prevents the bladder from emptying.
• Tumors in the abdomen that surround and obstruct the ureters.
• Kidney stones. Usually, kidney stones affect only one kidney and do not cause kidney failure. However, if there is only one kidney present, a kidney stone may cause the lone kidney to fail.

Chronic renal failure develops over months and years. The most common causes of chronic renal failure are related to:

• poorly controlled diabetes,
• poorly controlled high blood pressure

Acute Kidney Failure Symptoms

The following symptoms may occur with acute kidney failure. Some people have no symptoms, at least in the early stages. The symptoms may be very subtle.

• Decreased urine production
• Body swelling
• Problems concentrating
• Confusion
• Fatigue
• Lethargy
• Nausea, vomiting
• Diarrhea
• Abdominal pain
• Metallic taste in the mouth

Seizures and coma may occur in very severe acute kidney failure

What is the treatment for kidney failure?

Prevention is always the goal with kidney failure. Chronic diseases such as hypertension and diabetes are devastating because of the damage that they can do to kidneys and other organs. Lifelong diligence is important in keeping blood sugar and blood pressure within normal limits. Specific treatments are dependent upon the underlying diseases.

Once kidney failure is present, the goal is to prevent further deterioration of renal function. If ignored, the kidneys will progress to complete failure, but if underlying illnesses are addressed and treated aggressively, kidney function can be preserved, though not always improved.

Dialysis

Dialysis cleanses the body of waste products in the body by use of filter systems. There are two types of dialysis; 1) hemodialysis, and 2) peritoneal dialysis.

Kidney transplantation

If kidney failure occurs and is non-reversible, kidney transplantation is an alternative option to dialysis. If the patient is an appropriate candidate, the health care practitioner will contact an organ transplant center to arrange evaluation to see if the patient is suitable for this treatment. If so, the search for a donor begins. Sometimes, family members have compatible tissue types and, if they are willing, may donate a kidney. Otherwise, the patient will be placed on the organ transplant list that is maintained by the United Network of Organ Sharing.

Not all hospitals are capable of performing kidney transplants. The patient may have to travel to undergo their operation. The most successful programs are those that do many transplants every year.

While kidney transplants have become more routine, they still carry some risk. The patient will need to take anti-rejection medications that reduce the ability of the immune system to fight infection. The body can try to reject the kidney or the transplanted kidney may fail to work. As with any operation, there is a risk of bleeding and infection.

Kidney transplants may provide better quality of life than dialysis. After one year, 95% of transplanted kidneys are still functioning and after five years the number is 80%. It seems that the longer a patient is on dialysis, the shorter the life of the transplanted kidney.

If the transplanted kidney fails, the alternative is another kidney transplant or a return to dialysis.

Kidney Failure At A Glance

• Kidneys are the organs that help filter waste products from the blood. They are also involved in regulating blood pressure, electrolyte balance, and red blood cell production in the body.
• There are numerous causes of kidney failure, and treatment of the underlying disease may be the first step in correcting the kidney abnormality.
• Some causes of kidney failure are treatable and the kidney function may return to normal. Unfortunately, kidney failure may be progressive in other situations and may be irreversible.
• Symptoms of kidney failure are due to the build-up of waste products in the body that may cause weakness, shortness of breath, lethargy, and confusion. Inability to remove potassium from the bloodstream may lead to abnormal heart rhythms and sudden death. Initially, there may be no symptoms of kidney failure.
• The diagnosis of kidney failure usually is made by blood tests measuring BUN, creatinine, and glomerular filtration rate (GFR).
• Treatment of the underlying cause of kidney failure may return kidney function to normal. Lifelong efforts to control blood pressure and diabetes may be the best way to prevent chronic kidney disease and its progression to kidney failure. Usually, kidney function gradually decreases over time.
• If the kidneys fail completely, the only treatment options available may be dialysis or transplant.