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 electrolytes 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 of 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.)

The kidneys have the ability to monitor the amount of body fluid, the concentrations of electrolytes like sodium and potassium, and the acid-base balance of the body. They filter waste products of body metabolism, like urea from protein metabolism and uric acid from DNA breakdown. Two waste products in the blood can be measured: blood urea nitrogen (BUN) and creatinine (Cr).

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.

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.

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 are:

• Hypovolemia (low blood volume) due to blood loss
  
  
• Dehydration from loss of body fluid (vomiting, diarrhea, sweating, fever )
  
  
• Poor intake of fluids
  
  
• Medication, for example, diuretics ("water pills") may cause excessive water loss.
  
  
• Loss of blood supply to the kidney due to obstruction of the renal artery or vein.

Renal causes (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. Others are antibiotics like aminoglycosides [gentamicin (Garamycin), tobramycin], lithium (Eskalith, Lithobid), iodine-containing medications such as those injected for radiology dye studies.
  
  
• Rhabdomyolysis: This is a situation in which there is significant muscle breakdown in the body, and the degeneration products of muscle fibers clog the filtering system of the kidneys. Often occurring because of trauma and crush injuries, it can also be caused by some medications used to treat high cholesterol.
  
  
• Multiple Myeloma
  
  
• Acute glomerulonephritis or inflammation of the glomeruli, the filtering system of the kidneys. Many diseases can cause this inflammation including systemic lupus erythematosus, Wegener's granulomatosis, and Goodpasture syndrome.

Post renal causes (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 when there is no place for the urine to go as the kidneys continue to work. When the pressure increases enough, the kidneys 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

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
  
  
• Chronic glomerulonephritis

Less common causes:

• Polycystic Kidney Disease
  
  
• Reflux nephropathy
  
  
• Kidney stones
  
  
• Prostate disease

The Facts About Chronic Kidney Disease (CKD)

• 26 million Americans have CKD and another 20 million more are at increased risk.
• Early detection can help prevent the progression of kidney disease to kidney failure.
• Heart disease is the major cause of death for all people with CKD.
• Glomerular filtration rate (GFR) is the best estimate of kidney function.
• Hypertension causes CKD and CKD causes hypertension.
• Persistent proteinuria means CKD.
• High risk groups include those with diabetes, hypertension and family history of kidney disease.
• African Americans, Hispanics, Pacific Islanders, Native Americans and Seniors are at increased risk.
• Three simple tests can detect CKD: blood pressure, urine albumin and serum creatinine.

How do your kidneys help maintain health?

In addition to removing wastes and fluid from your body, your kidneys perform these other important jobs:

• Regulate your body water and other chemicals in your blood such as sodium, potassium, phosphorus and calcium
• Remove drugs and toxins introduced into your body
• Release hormones into your blood to help your body:
  1. regulate blood pressure
  2. make red blood cells
  3. promote strong bones.

What is chronic kidney disease (CKD)?

Chronic kidney disease includes conditions that damage your kidneys and decrease their ability to keep you healthy by doing the jobs listed. If kidney disease gets worse, wastes can build to high levels in your blood and make you feel sick. You may develop complications like high blood pressure, anemia (low blood count), weak bones, poor nutritional health and nerve damage. Also, kidney disease increases your risk of having heart and blood vessel disease. These problems may happen slowly over a long period of time. Chronic kidney disease may be caused by diabetes, high blood pressure and other disorders. Early detection and treatment can often keep chronic kidney disease from getting worse. When kidney disease progresses, it may eventually lead to kidney failure, which requires dialysis or a kidney transplant to maintain life.

What causes CKD?

The two main causes of chronic kidney disease are diabetes and high blood pressure, which are responsible for up to two-thirds of the cases. Diabetes happens when your blood sugar is too high, causing damage to many organs in your body, including the kidneys and heart, as well as blood vessels, nerves and eyes. High blood pressure, or hypertension, occurs when the pressure of your blood against the walls of your blood vessels increases. If uncontrolled, or poorly controlled, high blood pressure can be a leading cause of heart attacks, strokes and chronic kidney disease. Also, chronic kidney disease can cause high blood pressure.

Other conditions that affect the kidneys are:

• Glomerulonephritis, a group of diseases that cause inflammation and damage to the kidney's filtering units. These disorders are the third most common type of kidney disease.
• Inherited diseases, such as polycystic kidney disease, which causes large cysts to form in the kidneys and damage the surrounding tissue.
• Malformations that occur as a baby develops in its mother's womb. For example, a narrowing may occur that prevents normal outflow of urine and causes urine to flow back up to the kidney. This causes infections and may damage the kidneys.
• Lupus and other diseases that affect the body's immune system.
• Obstructions caused by problems like kidney stones, tumors or an enlarged prostate gland in men.
• Repeated urinary infections.

What are the symptoms of CKD?

Most people may not have any severe symptoms until their kidney disease is advanced. However, you may notice that you:

• feel more tired and have less energy
• have trouble concentrating
• have a poor appetite
• have trouble sleeping
• have muscle cramping at night
• have swollen feet and ankles
• have puffiness around your eyes, especially in the morning
• have dry, itchy skin
• need to urinate more often, especially at night.

Anyone can get chronic kidney disease at any age. However, some people are more likely than others to develop kidney disease. You may have an increased risk for kidney disease if you:

• have diabetes
• have high blood pressure
• have a family history of chronic kidney disease
• are older
• belong to a population group that has a high rate of diabetes or high blood pressure, such as African Americans, Hispanic Americans, Asian, Pacific Islanders, and American Indians.

Kidney Transplant &Medical Treatment

The most critical part of kidney transplantation is preventing rejection of the graft kidney.

• Different transplant centers use different drug combinations to fight rejection of a transplanted kidney.
  
  
• The drugs work by suppressing your immune system, which is programmed to reject anything "foreign," such as a new organ.
  
  
• Like any medication, these drugs can have unpleasant side effects.
  
  
• Some of the most common immune-suppressing drugs used in transplantation are described here.
  
  
  • Cyclosporine: This drug interferes with communication between the T cells of the immune system. It is started immediately after the transplant to suppress your immune system and continued indefinitely. Common side effects include tremor, high blood pressure, and kidney damage. These side effects are usually related to the dose and can often be reversed with proper dosing.
    
    
  • Corticosteroids: These drugs block T-cell communication as well. They are usually given at high doses for a short period immediately after the transplant and again if rejection is suspected. Corticosteroids have many different side effects, including easy bruising of the skin, osteoporosis, avascular necrosis (bone death), high blood pressure, high blood sugar, stomach ulcers, weight gain, acne, mood swings, and a round face. Because of these side effects, many transplant centers are trying to reduce the maintenance dose of the drug as much as possible or even to replace it with other drugs.
    
    
  • Azathioprine: This drug slows the production of T cells in the immune system. Azathioprine is usually used for long-term maintenance of immunosuppression. The most common side effects of this drug are suppression of the bone marrow, which produces blood cells, and liver damage. Many transplant centers are now using a newer drug called mycophenolate mofetil instead of azathioprine.
    
    
  • Newer antirejection drugs include tacrolimus, sirolimus, and mizoribin, among others. These drugs are now being used to try to reduce side effects and to replace drugs after episodes of rejection.
    
    
  • Other costly and experimental treatments include using antibodies to attack specific parts of the immune system to decrease its response.