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If your blood is low in red blood cells, you have anemia. Red blood cells carry oxygen (O2) to tissues and organs throughout your body and enable them to use the energy from food. Without oxygen, these tissues and organs—particularly the heart and brain—may not do their jobs as well as they should. For this reason, if you have anemia, you may tire easily and look pale. Anemia may also contribute to heart problems.

Anemia is common in people with kidney disease. Healthy kidneys produce a hormone called erythropoietin, or EPO, which stimulates the bone marrow to produce the proper number of red blood cells needed to carry oxygen to vital organs. Diseased kidneys, however, often don’t make enough EPO. As a result, the bone marrow makes fewer red blood cells. Other common causes of anemia include loss of blood from hemodialysis and low levels of iron and folic acid. These nutrients from food help young red blood cells make hemoglobin (Hgb), their main oxygen-carrying protein.
Healthy kidneys produce a hormone called erythropoietin, or EPO, which stimulates the bone marrow to make red blood cells needed to carry oxygen (O2) throughout the body.
Diseased kidneys don’t make enough EPO, and bone marrow then makes fewer red blood cells.

Laboratory Tests
A complete blood count (CBC), a laboratory test performed on a sample of your blood, includes a determination of your hematocrit (Hct), the percentage of the blood that consists of red blood cells. The CBC also measures the amount of Hgb in your blood. The range of normal Hct and Hgb in women who menstruate is slightly lower than for healthy men or healthy postmenopausal women. The Hgb is usually about one-third the value of the Hct.

 
When Anemia Begins
Anemia may begin to develop in the early stages of kidney disease, when you still have 20 percent to 50 percent of your normal kidney function. This partial loss of kidney function is often called chronic renal insufficiency. Anemia tends to worsen as kidney disease progresses. End-stage kidney failure, the point at which dialysis or kidney transplantation becomes necessary, doesn’t occur until you have only about 10 percent of your kidney function remaining. Nearly everyone with end-stage kidney failure has anemia.
Diagnosis
If you have lost at least half of normal kidney function (based on your glomerular filtration rate calculated using your serum creatinine measurement) and have a low Hct, the most likely cause of anemia is decreased EPO production. The National Kidney Foundation’s Dialysis Outcomes Quality Initiative (DOQI) recommends that doctors begin a detailed evaluation of anemia in men and postmenopausal women on dialysis when the Hct value falls below 37 percent. For women of childbearing age, evaluation should begin when the Hct falls below 33 percent. The evaluation will include tests for iron deficiency and blood loss in the stool to be certain there are no other reasons for the anemia.

When to Evaluate Dialysis Patients for Anemia   Hematocrit (Hct) Hemoglobin (Hgb)
Women who menstruate less than 33% less than 11 g/dL
All men and postmenopausal women less than 37% less than 12 g/dL
Source: The National Kidney Foundation’s Dialysis Outcomes Quality Initiative.

Treatment
EPO
If no other cause for EPO deficiency is found, it can be treated with a genetically engineered form of the hormone, which is usually injected under the skin two or three times a week. Hemodialysis patients who can’t tolerate EPO shots may receive the hormone intravenously during treatment, but this method requires a larger, more expensive dose and may not be as effective. DOQI recommends that patients treated with EPO therapy should achieve a target Hgb of 11 to 12 g/dL.

Iron
Many people with kidney disease need both EPO and iron supplements to raise their Hct to a satisfactory level. If your iron levels are too low, EPO won’t help and you’ll continue to experience the effects of anemia. You may be able to take an iron pill, but many studies show that iron pills don’t work as well in people with kidney failure as iron given intravenously. Iron is injected directly into an arm or into the tube that returns blood to your body during hemodialysis.

A nurse or doctor will give you a test dose because a very small number of people (less than 1 percent) have a bad reaction to iron injections. If you begin to wheeze or have trouble breathing, your health care provider can administer epinephrine or corticosteroids to counter the reaction. Even though the risk is small, you’ll be asked to sign a form stating that you understand the possible reaction and that you agree to have the treatment. Talk with your health care provider if you have any questions.

In addition to measuring your Hct and Hgb, your tests will also include two measurements to show whether you have enough iron.

Your ferritin level indicates the amount of iron stored in your body. According to DOQI guidelines, your ferritin score should be no less than 100 micrograms per liter (mcg/L) and no more than 800 mcg/L.

TSAT stands for transferrin saturation, a score that indicates how much iron is available to make red blood cells. DOQI guidelines call for a TSAT score between 20 percent and 50 percent.

Other Causes of Anemia
In addition to EPO and iron, a few people may also need vitamin B12 and folic acid supplements.

If EPO, iron, vitamin B12, and folic acid all fail, your doctor should look for other causes such as sickle cell disease or an inflammatory problem. At one time, aluminum poisoning contributed to anemia in people with kidney failure because many phosphate binders used to treat bone disease caused by kidney failure were antacids that contained aluminum. But aluminum-free alternatives are now widely available. Be sure your phosphate binder and your other drugs are free of aluminum.

Anemia keeps many people with kidney disease from feeling their best. But EPO treatments help most patients raise their Hgb, feel better, live longer, and have more energy.
Hope through Research
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), through its Division of Kidney, Urologic, and Hematologic Diseases, supports several programs and studies devoted to improving treatment for patients with progressive kidney disease and end-stage kidney failure, which is sometimes called end-stage renal disease or ESRD, including patients on hemodialysis:

The End-Stage Renal Disease Program. This program promotes research to reduce medical problems from bone, blood, nervous system, metabolic, gastrointestinal, cardiovascular, and endocrine abnormalities in end-stage kidney failure and to improve the effectiveness of dialysis and transplantation. The research focuses on reuse of hemodialysis membranes and on using alternative dialyzer sterilization methods; on devising more efficient, biocompatible membranes; on refining high-flux hemodialysis; and on developing criteria for dialysis adequacy. The program also seeks to increase kidney graft and patient survival and to maximize quality of life.

The Frequent Hemodialysis Network. This multicenter clinical trial will test whether receiving hemodialysis more than three times a week provides better outcomes than the normal schedule of three sessions per week.
The U.S. Renal Data System (USRDS). This national data system collects, analyzes, and distributes information about the use of dialysis and transplantation to treat kidney failure in the United States. The USRDS is funded directly by the NIDDK in conjunction with the Centers for Medicare & Medicaid Services. The USRDS publishes an Annual Data Report, which characterizes the total population of people being treated for kidney failure; reports on incidence, prevalence, mortality rates, and trends over time; and develops data on the effects of various treatment modalities. The report also helps identify problems and opportunities for more focused special studies of renal research issues.

The Hemodialysis Vascular Access Clinical Trials Consortium is conducting a series of multicenter, randomized, placebo-controlled clinical trials of drug therapies to reduce the failure and complication rate of arteriovenous grafts and fistulas in hemodialysis. Recently developed antithrombotic agents and drugs to inhibit cytokines are being evaluated in these large clinical trials.

Source: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health

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Blood Pressure Medicines

Scientists have made great progress in developing methods that slow the onset and progression of kidney disease in people with diabetes. Drugs used to lower blood pressure can slow the progression of kidney disease significantly. Two types of drugs, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), have proven effective in slowing the progression of kidney disease. Many people require two or more drugs to control their blood pressure. In addition to an ACE inhibitor or an ARB, a diuretic can also be useful. Beta blockers, calcium channel blockers, and other blood pressure drugs may also be needed.

An example of an effective ACE inhibitor is lisinopril (Prinivil, Zestril), which doctors commonly prescribe for treating kidney disease of diabetes. The benefits of lisinopril extend beyond its ability to lower blood pressure: it may directly protect the kidneys’ glomeruli. ACE inhibitors have lowered proteinuria and slowed deterioration even in people with diabetes who did not have high blood pressure.

An example of an effective ARB is losartan (Cozaar), which has also been shown to protect kidney function and lower the risk of cardiovascular events.

Any medicine that helps patients achieve a blood pressure target of 130/80 or lower provides benefits. Patients with even mild hypertension or persistent microalbuminuria should consult a health care provider about the use of antihypertensive medicines.

Moderate-protein Diets

In people with diabetes, excessive consumption of protein may be harmful. Experts recommend that people with kidney disease of diabetes consume the recommended dietary allowance for protein, but avoid high-protein diets. For people with greatly reduced kidney function, a diet containing reduced amounts of protein may help delay the onset of kidney failure. Anyone following a reduced-protein diet should work with a dietitian to ensure adequate nutrition.

Intensive Management of Blood Glucose

Antihypertensive drugs and low-protein diets can slow CKD. A third treatment, known as intensive management of blood glucose or glycemic control, has shown great promise for people with diabetes, especially for those in the early stages of CKD.

The human body normally converts food to glucose, the simple sugar that is the main source of energy for the body’s cells. To enter cells, glucose needs the help of insulin, a hormone produced by the pancreas. When a person does not make enough insulin, or the body does not respond to the insulin that is present, the body cannot process glucose, and it builds up in the bloodstream. High levels of glucose in the blood lead to a diagnosis of diabetes.

Intensive management of blood glucose is a treatment regimen that aims to keep blood glucose levels close to normal. The regimen includes testing blood glucose frequently, administering insulin throughout the day on the basis of food intake and physical activity, following a diet and activity plan, and consulting a health care team regularly. Some people use an insulin pump to supply insulin throughout the day.

A number of studies have pointed to the beneficial effects of intensive management of blood glucose. In the Diabetes Control and Complications Trial supported by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), researchers found a 50 percent decrease in both development and progression of early diabetic kidney disease in participants who followed an intensive regimen for controlling blood glucose levels. The intensively managed patients had average blood glucose levels of 150 milligrams per deciliter—about 80 milligrams per deciliter lower than the levels observed in the conventionally managed patients. The United Kingdom Prospective Diabetes Study, conducted from 1976 to 1997, showed conclusively that, in people with improved blood glucose control, the risk of early kidney disease was reduced by a third. Additional studies conducted over the past decades have clearly established that any program resulting in sustained lowering of blood glucose levels will be beneficial to patients in the early stages of CKD

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Complete and irreversible kidney failure is sometimes called end-stage renal disease, or ESRD. If your kidneys stop working completely, your body fills with extra water and waste products. This condition is called uremia. Your hands or feet may swell. You will feel tired and weak because your body needs clean blood to function properly.

Untreated uremia may lead to seizures or coma and will ultimately result in death. If your kidneys stop working completely, you will need to undergo dialysis or kidney transplantation.

Dialysis

The two major forms of dialysis are hemodialysis and peritoneal dialysis. In hemodialysis, your blood is sent through a filter that removes waste products. The clean blood is returned to your body. Hemodialysis is usually performed at a dialysis center three times per week for 3 to 4 hours.

In peritoneal dialysis, a fluid is put into your abdomen. This fluid captures the waste products from your blood. After a few hours, the fluid containing your body’s wastes is drained away. Then, a fresh bag of fluid is dripped into the abdomen. Patients can perform peritoneal dialysis themselves. Patients using continuous ambulatory peritoneal dialysis (CAPD) change fluid four times a day. Another form of peritoneal dialysis, called continuous cycling peritoneal dialysis (CCPD), can be performed at night with a machine that drains and refills the abdomen automatically.

Transplantation

A donated kidney may come from an anonymous donor who has recently died or from a living person, usually a relative. The kidney that you receive must be a good match for your body. The more the new kidney is like you, the less likely your immune system is to reject it. Your immune system protects you from disease by attacking anything that is not recognized as a normal part of your body. So your immune system will attack a kidney that appears too “foreign.” You will take special drugs to help trick your immune system so it does not reject the transplanted kidney.

Unfortunately, chronic kidney disease often cannot be cured. But if you are in the early stages of a kidney disease, you may be able to make your kidneys last longer by taking certain steps. You will also want to be sure that risks for heart attack and stroke are minimized, since CKD patients are susceptible to these problems.

• If you have diabetes, watch your blood glucose closely to keep it under control. Consult your doctor for the latest in treatment.
• Avoid pain pills that may make your kidney disease worse. Check with your doctor before taking any medicine.

Blood Pressure

People with reduced kidney function (a high creatinine level in the blood or a low creatinine clearance) should have their blood pressure controlled, and an ACE inhibitor or an ARB should be one of their medications. Many people will require two or more types of medication to keep their blood pressure below 130/80 mm Hg. A diuretic is an important addition to the ACE inhibitor or ARB.

Diet

People with reduced kidney function need to be aware that some parts of a normal diet may speed their kidney failure.

Protein. Protein is important to your body. It helps your body repair muscles and fight disease. Protein comes mostly from meat. As discussed in an earlier section, healthy kidneys take wastes out of the blood but leave protein. Impaired kidneys may fail to separate the protein from the wastes.

Some doctors tell their kidney patients to limit the amount of protein they eat so that the kidneys have less work to do. But you cannot avoid protein entirely. You may need to work with a dietitian to find the right food plan.

Cholesterol. Another problem that may be associated with kidney failure is too much cholesterol (koh-LES-tuh-rawl) in your blood. High levels of cholesterol may result from a high-fat diet.

Cholesterol can build up on the inside walls of your blood vessels. The buildup makes pumping blood through the vessels harder for your heart and can cause heart attacks and strokes.

Smoking. Smoking not only increases the risk of kidney disease, it contributes to deaths from strokes and heart attacks in people with CKD. You should try your best to stop smoking.

Sodium. Sodium is a chemical found in salt and other foods. Sodium in your diet may raise your blood pressure, so you should limit foods that contain high levels of sodium. High-sodium foods include canned or processed foods like frozen dinners and hot dogs.

Potassium. Potassium is a mineral found naturally in many fruits and vegetables, like oranges, potatoes, bananas, dried fruits, dried beans and peas, and nuts. Healthy kidneys measure potassium in your blood and remove excess amounts. Diseased kidneys may fail to remove excess potassium, and with very poor kidney function, high potassium levels can affect the heart rhythm.

Treating Anemia

Anemia is a condition in which the blood does not contain enough red blood cells. These cells are important because they carry oxygen throughout the body. If you are anemic, you will feel tired and look pale. Healthy kidneys make the hormone EPO, which stimulates the bones to make red blood cells. Diseased kidneys may not make enough EPO. You may need to take injections of a man-made form of EPO.

Preparing for End-Stage Renal Disease

As your kidney disease progresses, you will need to make several decisions. You will need to learn about your options for treating ESRD so that you can make an informed choice between hemodialysis, peritoneal dialysis, and transplantation

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Since you can have kidney disease without any symptoms, your doctor may first detect the condition through routine blood and urine tests. The National Kidney Foundation recommends three simple tests to screen for kidney disease: a blood pressure measurement, a spot check for protein or albumin in the urine (proteinuria), and a calculation of glomerular filtration rate (GFR) based on a serum creatinine measurement. Measuring urea nitrogen in the blood provides additional information.

Blood Pressure Measurement

High blood pressure can lead to kidney disease. It can also be a sign that your kidneys are already impaired. The only way to know whether your blood pressure is high is to have a health professional measure it with a blood pressure cuff. The result is expressed as two numbers. The top number, which is called the systolic pressure, represents the pressure when your heart is beating. The bottom number, which is called the diastolic pressure, shows the pressure when your heart is resting between beats. Your blood pressure is considered normal if it stays below 120/80 (expressed as “120 over 80”). The NHLBI recommends that people with kidney disease use whatever therapy is necessary, including lifestyle changes and medicines, to keep their blood pressure below 130/80.

Microalbuminuria and Proteinuria

Healthy kidneys take wastes out of the blood but leave protein. Impaired kidneys may fail to separate a blood protein called albumin from the wastes. At first, only small amounts of albumin may leak into the urine, a condition known as microalbuminuria, a sign of deteriorating kidney function. As kidney function worsens, the amount of albumin and other proteins in the urine increases, and the condition is called proteinuria. Your doctor may test for protein using a dipstick in a small sample of your urine taken in the doctor’s office. The color of the dipstick indicates the presence or absence of proteinuria.

A more sensitive test for protein or albumin in the urine involves laboratory measurement and calculation of the protein-to-creatinine or albumin-to-creatinine ratio. This test should be used to detect kidney disease in people at high risk, especially those with diabetes. If your first laboratory test shows high levels of protein, another test should be done 1 to 2 weeks later. If the second test also shows high levels of protein, you have persistent proteinuria and should have additional tests to evaluate your kidney function.

Glomerular Filtration Rate (GFR) Based on Creatinine Measurement

GFR is a calculation of how efficiently the kidneys are filtering wastes from the blood. A traditional GFR calculation requires an injection into the bloodstream of a substance that is later measured in a 24-hour urine collection. Recently, scientists found they could calculate GFR without an injection or urine collection. The new calculation requires only a measurement of the creatinine in a blood sample.

Creatinine is a waste product in the blood created by the normal breakdown of muscle cells during activity. Healthy kidneys take creatinine out of the blood and put it into the urine to leave the body. When kidneys are not working well, creatinine builds up in the blood.

In the lab, your blood will be tested to see how many milligrams of creatinine are in one deciliter of blood (mg/dL). Creatinine levels in the blood can vary, and each laboratory has its own normal range, usually 0.6 to 1.2 mg/dL. If your creatinine level is only slightly above this range, you probably will not feel sick, but the elevation is a sign that your kidneys are not working at full strength. One formula for estimating kidney function equates a creatinine level of 1.7 mg/dL for most men and 1.4 mg/dL for most women to 50 percent of normal kidney function. But because creatinine values are so variable and can be affected by diet, a GFR calculation is more accurate for determining whether a person has reduced kidney function.

The new GFR calculation uses the patient’s creatinine measurement along with weight, age, and values assigned for sex and race. Some medical laboratories may make the GFR calculation when a creatinine value is measured and include it on their lab report.

Blood Urea Nitrogen (BUN)

Blood carries protein to cells throughout the body. After the cells use the protein, the remaining waste product is returned to the blood as urea, a compound that contains nitrogen. Healthy kidneys take urea out of the blood and put it in the urine. If your kidneys are not working well, the urea will stay in the blood.

A deciliter of normal blood contains 7 to 20 milligrams of urea. If your BUN is more than 20 mg/dL, your kidneys may not be working at full strength. Other possible causes of an elevated BUN include dehydration and heart failure.

Additional Tests for Kidney Disease

If blood and urine tests indicate reduced kidney function, your doctor may recommend additional tests to help identify the cause of the problem.

Renal imaging. Methods of renal imaging (taking pictures of the kidneys) include ultrasound, computed tomography (CT scan), and magnetic resonance imaging (MRI). These tools are most helpful in finding unusual growths or blockages to the flow of urine.

Renal biopsy. Your doctor may want to see a tiny piece of your kidney tissue under a microscope. To obtain this tissue sample, the doctor will perform a renal biopsy—a hospital procedure in which the doctor inserts a needle through your skin into the back of the kidney. The needle retrieves a strand of tissue about 1/2 to 3/4 of an inch long. For the procedure, you will lie on your stomach on a table and receive local anesthetic to numb the skin. The sample tissue will help the doctor identify problems at the cellular level.

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People in the early stages of kidney disease usually do not feel sick at all.

If your kidney disease gets worse, you may need to urinate more often or less often. You may feel tired or itchy. You may lose your appetite or experience nausea and vomiting. Your hands or feet may swell or feel numb. You may get drowsy or have trouble concentrating. Your skin may darken. You may have muscle cramps.

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Many factors that influence the speed of kidney failure are not completely understood. Researchers are still studying how protein in the diet and cholesterol levels in the blood affect kidney function.

Acute Renal Failure

Some kidney problems happen quickly, like an accident that injures the kidneys. Losing a lot of blood can cause sudden kidney failure. Some drugs or poisons can make your kidneys stop working. These sudden drops in kidney function are called acute renal failure (ARF).

ARF may lead to permanent loss of kidney function. But if your kidneys are not seriously damaged, acute renal failure may be reversed.

Chronic Kidney Disease

Most kidney problems, however, happen slowly. You may have “silent” kidney disease for years. Gradual loss of kidney function is called chronic kidney disease (CKD) or chronic renal insufficiency. People with CKD may go on to permanent kidney failure. They also have a high risk of dying from a stroke or heart attack.

End-Stage Renal Disease

Total or nearly total and permanent kidney failure is called end-stage renal disease (ESRD). People with ESRD must undergo dialysis or transplantation to stay alive.

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Most kidney diseases attack the nephrons, causing them to lose their filtering capacity. Damage to the nephrons may happen quickly, often as the result of injury or poisoning. But most kidney diseases destroy the nephrons slowly and silently. Only after years or even decades will the damage become apparent. Most kidney diseases attack both kidneys simultaneously.

The two most common causes of kidney disease are diabetes and high blood pressure. If your family has a history of any kind of kidney problems, you may be at risk for kidney disease.

Diabetic Nephropathy

Diabetes is a disease that keeps the body from using glucose (sugar) as it should. If glucose stays in your blood instead of breaking down, it can act like a poison. Damage to the nephrons from unused glucose in the blood is called diabetic nephropathy. If you keep your blood glucose levels down, you can delay or prevent diabetic nephropathy.

High Blood Pressure

High blood pressure can damage the small blood vessels in your kidneys. The damaged vessels cannot filter wastes from your blood as they are supposed to.

Your doctor may prescribe blood pressure medication. Blood pressure medicines called angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) have been found to protect the kidneys even more than other medicines that lower blood pressure to similar levels. The National Heart, Lung, and Blood Institute (NHLBI), one of the National Institutes of Health, recommends that people with diabetes or reduced kidney function should keep their blood pressure below 130/80 mm Hg.

Glomerular Diseases

Several different types of kidney disease are grouped together under this category, including autoimmune diseases, infection-related diseases, and sclerotic diseases. As the name indicates, glomerular diseases attack the tiny blood vessels (glomeruli) within the kidney. The most common primary glomerular diseases include membranous nephropathy, IgA nephropathy, and focal segmental glomerulosclerosis. Protein, blood, or both in the urine are often the first signs of these diseases. They can slowly destroy kidney function. Blood pressure control is important with any kidney disease. Treatments for glomerular diseases may include immunosuppressive drugs or steroids to reduce inflammation and proteinuria, depending on the specific disease.

Inherited and Congenital Kidney Diseases

Some kidney diseases result from hereditary factors. Polycystic kidney disease (PKD), for example, is a genetic disorder in which many cysts grow in the kidneys. PKD cysts can slowly replace much of the mass of the kidneys, reducing kidney function and leading to kidney failure.

Some kidney problems may show up when a child is still developing in the womb. Examples include autosomal recessive PKD, a rare form of PKD, and other developmental problems that interfere with the normal formation of the nephrons. The signs of kidney disease in children vary. A child may grow unusually slowly, may vomit often, or may have back or side pain. Some kidney diseases may be “silent” for months or even years.

If your child has a kidney disease, your child’s doctor should find it during a regular checkup. Be sure your child sees a doctor regularly. The first sign of a kidney problem may be high blood pressure, a low number of red blood cells (anemia), or blood or protein in the child’s urine. If the doctor finds any of these problems, further tests may be necessary, including additional blood and urine tests or radiology studies. In some cases, the doctor may need to perform a biopsy—removing a tiny piece of the kidney to examine under a microscope.

Some hereditary kidney diseases may not be detected until adulthood. The most common form of PKD was once called “adult PKD” because the symptoms of high blood pressure and renal failure usually do not occur until patients are in their twenties or thirties. But with advances in diagnostic imaging technology, doctors have found cysts in children and adolescents before any symptoms appear.

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If you have a problem with urine leakage or blocked urine flow, your doctor or nurse may be able to help. One of the tools they may use to evaluate the cause of your symptoms is urodynamic testing.

Several muscles, organs, and nerves are involved in collecting, storing, and releasing urine. The kidneys form urine by filtering wastes and extra water from the bloodstream. The ureters are tubes that carry urine from the kidneys to the bladder. Normally urine flows in one direction. If urine backs up toward the kidneys, infections and kidney damage can occur.

The bladder, a hollow muscular organ shaped like a balloon, sits in the pelvis and is held in place by ligaments attached to other organs and to the pelvic bones. The bladder stores urine until you are ready to empty it. It swells into a round shape when it is full and gets smaller as it empties. A healthy bladder can hold up to 16 ounces (2 cups) of urine comfortably. How frequently it fills depends on how much excess water your body is trying to get rid of.

The bladder opens into the urethra, the tube that allows urine to pass outside the body. Circular muscles called sphincters close tightly to keep urine from leaking. The involuntary leakage of urine is called incontinence.

Nerves in the bladder tell you when it is time to empty your bladder. When the bladder begins to fill with urine, you may notice a feeling that you need to urinate. The sensation becomes stronger as the bladder continues to fill and reaches its limit. At that point, nerves in the bladder send a message to the brain, and your urge to urinate intensifies.

When you are ready to urinate, the brain signals the sphincter muscles to relax. At the same time, the brain signals the bladder muscles to squeeze, thus allowing urine to flow through the urethra. When these signals occur in the correct order, normal urination occurs.

Problems in the urinary system can be caused by aging, illness, or injury. The muscles in and around your bladder and urethra tend to become weaker with age. Weak bladder muscles may result in your not being able to empty your bladder completely, leaving you at a higher risk for urinary tract infections. Weak muscles of the sphincters and pelvis can lead to urinary incontinence because the sphincter muscles cannot remain tight enough to hold urine in the bladder, or the bladder does not have enough support from the pelvic muscles to stay in its proper position.

Urodynamics is a study that assesses how the bladder and urethra are performing their job of storing and releasing urine. Urodynamic tests help your doctor or nurse see how well your bladder and sphincter muscles work and can help explain symptoms such as

• incontinence
• frequent urination
• sudden, strong urges to urinate
• problems starting a urine stream
• painful urination
• problems emptying your bladder completely
• recurrent urinary tract infections

These tests may be as simple as urinating behind a curtain while a doctor or nurse listens or more complicated, involving imaging equipment that films urination and pressure monitors that record the pressures of the bladder and urethra.

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A biopsy is a diagnostic test that involves collecting small pieces of tissue, usually through a needle, for examination under a microscope. A kidney biopsy can help find a diagnosis and determine the best course of treatment. Your doctor may recommend a kidney biopsy if you have any of the following conditions:

• hematuria which is blood in your urine
• proteinuria which is excessive protein in your urine
• impaired kidney function which causes excessive waste products in your blood

A pathologist will look at the kidney tissue samples to check for unusual deposits, scarring, or infecting organisms that would explain your condition. The doctor may discover that you have a condition that can be treated and cured. If you have progressive kidney failure, the biopsy may indicate how quickly the disease is advancing. A biopsy can also help explain why a transplanted kidney is not working properly.

Talk with your doctor about what information might be obtained from the biopsy and the risks involved so that you can help make a decision about whether a biopsy is worthwhile in your case.

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