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The prostate gland, or simply prostate, is a walnut-sized gland in men, which is located in front of the rectum just below the bladder. It acts to produce fluid that becomes a part of the semen. The prostate surrounds the first part of the urethra—the tube through which urine passes out of the body.

Prostate problems may include prostatitis, prostate enlargement or benign prostatic hyperplasia (BPH), and prostate cancer. These prostate problems may have similar symptoms. This is the reason why thorough testing is needed for accurate diagnosis and to rule out other health problems.

Tests for Prostate Problems

There are several tests that your doctor can perform or recommend, which include DRE, PSA Test, urinalysis, transrectal ultrasound, and prostate biopsy.

Digital Rectal Exam (DRE)

In this exam, the doctor inserts a lubricated, gloved finger in the rectum and feels the part of the prostate that lies next to it. The doctor can check for any lumps, irregularities, soft spots, or hard spots. If infection is suspected, the doctor might massage the prostate during DRE to obtain fluid for examination with a microscope.

Prostate-specific antigen (PSA) test

PSA blood testing may be recommended by the doctor, which may help rule out prostate cancer. PSA is a protein produced by the prostate, which is often higher in men who have prostate cancer. However, high PSA levels in the blood does not necessarily mean that a person has prostate cancer.

Urinalysis

In this test, the person is asked by the doctor or health care provider to provide a urine sample. The urine sample is tested with a dipstick or examined with a microscope.

Transrectal Ultrasound

The doctor may recommend a transrectal ultrasound if he or she suspects prostate cancer. In transrectal ultrasound, a probe slightly larger than a pen is inserted into the rectum. The probe directs high-frequency sound waves at the prostate, and the echo patterns produce an image of the gland on a television monitor. The image shows how big the prostate is. Also, it can show any irregularities in the prostate. This imaging test, however, cannot clearly identify tumors.

Prostate Biopsy

A biopsy of the prostate may be recommended by the doctor to confirm diagnosis of prostate cancer. In this procedure, the doctor can use the probe and the ultrasound images to guide a biopsy needle to the suspected tumor. Samples of prostate tissues are collected for examination with a microscope.

References:

The National Institute on Aging (NIA). Age Page: Prostate Problems. U.S. Department of Health and Human Services (Public Health Service), National Institutes of Health ((NIH). March 2008, Page last updated Aug 06, 2009

National Cancer Institute (NCI). What You Need To Know About™ Prostate Cancer. National Institutes of Health (NIH). November 20, 2008

National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC).Medical Tests for Prostate Problems. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). NIH Publication No. 07–5105, October 2006

Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.

Image Credit: NIDDK Image Library

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Page Last Revised: November 14, 2009

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Prostate cancer, or prostatic cancer, is a cancer that forms in tissues of the prostate. Prostate cancer usually occurs in older men.

The prostate is a gland about the size of a walnut, which wraps around the first part of the urethra—the tube that carries urine out of the bladder. It is located in front of the rectum and just below the bladder.

In prostate cancer, cells abnormally form, which often forms a mass of tissue called a growth or tumor. Prostate growths can be benign (meaning it is not cancer) or malignant (cancer).

Benign prostatic hyperplasia (BPH) is a non-cancerous growth of prostate cells. The prostate grows larger, which can squeeze the urethra that can partially or totally block the flow of urine. To learn more about BPH, please visit our Benign Prostatic Hyperplasia page.

Cancer cells in prostate cancer can spread by breaking away from the prostate tumor. These cancer cells that break away can travel through the blood or lymph vessels and can cause cancer in other parts of the body. The spread of cancer is called metastasis.

Treatment of prostate cancer is much more effective when the disease is found early and has not spread to other parts of the body.

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Risks for Prostate Cancer

Until now, no one knows exactly what causes prostate cancer. However, research has shown that men with certain risk factors are more likely than others to develop cancer of the prostate. Your chance of getting prostate cancer may be increased if you have the following risk factors:

 Age over 65. The chance of developing prostate cancer increases as you get older. According to the National Cancer Institute, most men with prostate cancer in the United States are over 65.

 Family history. Your risk is higher if your father or brother has had prostate cancer.

 Race. According to the National Institute on Aging, prostate cancer is most common among African-American men.

 Certain changes in the prostate. Men with cells called high-grade prostatic intraepithelial neoplasia (PIN) may increase the risk of prostate cancer. When viewed under a microscope, these prostate cells look abnormal.

 Certain changes in genes. Researchers have found specific regions on certain chromosomes that are linked to the risk of prostate cancer. According to the National Cancer Institute, a man who has a genetic change in one or more of these regions, the risk of prostate cancer may be increased. Other studies have shown that men with changes in certain genes, such as BRCA1 and BRCA2 have an increased risk of developing prostate cancer.

Having a risk factor, however, does not mean that a man will develop prostate cancer. Also, most men who have risk factors never develop the condition.

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Symptoms of Prostate Cancer

Early prostate cancer often does not cause symptoms. As the cancer grows, you may have trouble urinating. You may need to urinate often, especially at night or have a hard time starting or stopping the flow of urine.

Other signs and symptoms of prostate cancer include

 Painful or burning sensation during urination

 Blood in the urine (hematuria) or semen

 Painful ejaculation

 Pain in the back, hips or pelvis, or upper thighs

Often, these symptoms are not due to cancer. Other health problems, such as BPH or an infection may cause these symptoms. If you have any of these symptoms, you should inform your doctor so that problems can be diagnosed and treated.

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Diagnosing Prostate Cancer

To find out if your symptoms are caused by prostate cancer, your doctor will ask about your personal and family medical history. Your doctor will perform a physical exam. In the exam, your doctor will insert a lubricated, gloved finger into your rectum to feel your prostate and check for hard or lumpy areas. This exam is called a digital rectal exam.

Your doctor may also perform blood test for prostate-specific antigen (PSA) level. The prostate makes PSA. PSA levels may be high in men who have an enlarged prostate or prostate cancer.

The digital rectal exam and PSA test can detect a problem in the prostate. However, these tests can’t show whether the problem is cancer or a less serious condition. Your doctor may recommend an ultrasound exam, which takes computer pictures of your prostate.

To confirm the diagnosis, your doctor will likely recommend a biopsy of your prostate. Your doctor will get samples of prostate tissues to look for cancer cells. Performing a biopsy is the only sure way to diagnose prostate cancer.

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Treating Prostate Cancer

Treatment of prostate cancer depends on whether cancer is in part or the entire prostate or if it has spread to other parts of the body. It also depends on your age and overall health. The treatment that's best for one man may not be best for another. Talk with your doctor about the best treatment choice for you.

For cancer that has not spread from the prostate to other parts of the body, your doctor may suggest:

 Watchful waiting, which is also called “active surveillance.” If the cancer is growing slowly and not causing problems, you may decide not to treat it right away. Instead, your doctor will check regularly for changes in your condition. Older men with other health problems often choose this option.

 Surgery. The most common type of surgery removes the whole prostate and some nearby tissue. As with any surgery, there are risks. Talk to your doctor about keeping your sexual function.

 Radiation therapy. This treatment uses high-energy x-rays to kill cancer cells and shrink tumors. Talk with your doctor about possible side effects.

 Hormone therapy. Men who have radiation therapy may also be treated with hormone blockers. This is done if it seems likely that the cancer will come back. Hormone therapy is also used for prostate cancer that has spread beyond the prostate.

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References:

The National Institute on Aging (NIA). Age Page: Prostate Problems. U.S. Department of Health and Human Services (Public Health Service), National Institutes of Health ((NIH). March 2008, Page last updated Aug 06, 2009

National Cancer Institute (NCI). What You Need To Know About™ Prostate Cancer. National Institutes of Health (NIH). November 20, 2008

Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.

Seeley, R. et al: ESSENTIALS OF ANATOMY AND PHYSIOLOGY. 5th ed. McGraw – Hill, 2005.

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The number of nephrons is the same when a person is born. About a million of nephrons is found in each kidney.

The nephrons are the vital filtering units within the kidney. They help separate blood cells and fluid including wastes in the blood. Large substances and blood cells, such as red blood cells and white blood cells remain in the blood vessels while wastes, such as urea and excess fluids are allowed to pass through to become part of the urine.

In addition, the nephrons help regulate the body’s chemicals including sodium, potassium, and phosphorus.

Damage to most of the nephrons can lead to kidney failure. A person whose kidneys totally fail to function need to undergo dialysis or kidney transplantation to survive.

• The Nephron

References:

The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).NIH Publication No. 07–3195, August 2007

Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.

Seeley, R. et al: ESSENTIALS OF ANATOMY AND PHYSIOLOGY. 5th ed. McGraw – Hill, 2005.

Page Last Revised: December 7, 2010

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The organs of the urinary system and their functions.

The urinary system is the body’s primary system involved with excreting most of the body’s wastes and excess water. Also the integumentary and respiratory systems aid in excreting some of the body’s waste products. The urinary system consists of two kidneys, two ureters, a urinary bladder, and a urethra.

Generally, the kidneys are the ones responsible for filtering the blood and getting rid of wastes and excess water. The kidneys also help in controlling blood pressure, participate in forming vitamin D, and release erythropoietin—a hormone that stimulates the production of red blood cells.

These waste products and unwanted water, which comprises the urine, then pass through two tubes—one each kidney—, called ureters. The ureters act as passageway for urine to reach the urinary bladder. The urinary bladder or simply called bladder is a hollow, balloon-shaped, distensible organ, which expands as it is filled with urine and collapses when urine is emptied. The process of emptying urine is called urination or micturition. The bladder acts to store urine until it is time to empty. When urination occurs, urine is drained through the urethra—the last part of the urinary tract.

References:
National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).NIH Publication No. 07–3195, August 2007

Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.

Seeley, R. et al: ESSENTIALS OF ANATOMY AND PHYSIOLOGY. 5th ed. McGraw – Hill, 2005.

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Renal artery stenosis, or RAS, is a condition in which there is narrowing of one or both arteries that carry blood to the kidneys. The arteries carrying blood to the kidneys are called the renal arteries. RAS can cause reduction in kidney function and even elevated blood pressure.

In most cases, renal artery stenosis is caused by atherosclerosis, which causes hardening of the kidney arteries. Cholesterol deposits, called plaques, build up on the inner wall of one or both of the renal arteries, which makes the arterial wall hard and narrow. The narrowing of the artery causes reduction or even total blockage of blood supply to the kidney, which eventually results to kidney damage.

Left untreated, RAS can lead to kidney failure causing wastes and excess fluid to build up in the blood. With total kidney failure, a person needs to undergo dialysis or kidney transplantation to stay alive.

Renal Artery Stenosis Risk Factors

Many factors can put a person at risk for developing renal artery stenosis. Some of the common risk factors include

 Older people between the ages of 50 and 70

 Smoking

 Overweight or obesity

 High blood cholesterol levels

 Diabetes

 A family history of cardiovascular disease

 High blood pressure or hypertension—This can be a cause or a result of RAS.

Symptoms of Renal Artery Stenosis

The condition is considered as a silent disease because the condition may be present for many years without symptoms.

The first sign of renal artery stenosis may be hypertension, which stays elevated even after taking blood pressure medication. Renovascular hypertension is the term used for high blood pressure caused by RAS.

Diagnosis of Renal Artery Stenosis

A doctor cannot diagnose RAS based on blood pressure alone because other conditions can also cause blood pressure to become elevated. The doctor may suspect renal artery stenosis if a person suddenly develops high blood pressure and has no family history of high blood pressure, or if the person’s blood pressure is difficult to control.

The doctor may place a stethoscope on the front or side of the person to listen for bruit (BROO-ee)—a whooshing sound heard when blood flows through a narrowed (stenosed) blood vessel. The absence of this sound, however, does not exclude the possibility of RAS and more tests are needed.

For a more accurate diagnosis, getting a picture of the artery through imaging tests may be ordered by the doctor. Imaging tests may include ultrasound, angiogram, computerized tomography (CT) scans, and magnetic resonance angiograms (MRA).

Treatment of Renal Artery Stenosis

Goals of treatment include:

 Preventing RAS from getting worse

 Treating hypertension that results from RAS

 Relieving the blockage of the renal arteries

Lifestyle Changes

Making lifestyle changes is the first step in the treatment of RAS. Lifestyle changes that people with RAS can do include:

 Exercise
 Maintaining a healthy weight
 Choosing healthy foods
 Quit smoking

These lifestyle changes can help keep the blood vessels clean and flexible.

Blood Pressure Medications

Medications to control renovascular hypertension may be prescribed by the doctor. However, each type of blood pressure medicine has its own potential side effects. The choice of anti-hyperstensive drugs can be best determined by the doctor.

The doctor may also prescribe drugs that lower cholesterol to prevent plaques from forming in the arterial wall.

Surgery

Surgery may be recommended to treat advanced RAS, where the blood vessel is almost or completely blocked. Surgical procedure may be used to upen up the flow of blood to the kidney. Different types of surgical procedures for RAS include:

 Angioplasty and stenting. Angioplasty is a procedure in which a catheter is put into the renal artery, usually through the groin, just as in a conventional angiogram. In addition, for angioplasty, a tiny balloon at the end of the catheter can be inflated to flatten the plaque against the wall of the artery. Then your doctor may position a small mesh tube, called a stent, to keep plaque flattened and the artery open.

 Endarterectomy. In an endarterectomy, a vascular surgeon cleans out the plaque, leaving the inside lining of the artery smooth and clear.

 Bypass surgery. To create a bypass, a vascular surgeon uses a vein or synthetic tube to connect the kidney to the aorta. This new path serves as an alternate route for blood to flow around the blocked artery into the kidney.

Reference:

National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). NIH Publication No. 07–6020, May 2007

Image Credit: NIDDK Image Library

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The renal arteries are blood vessels that carry blood to the kidneys. They directly branch off from the abdominal aorta. The aorta is the largest artery of the body and is the main blood vessel from the heart that supplies blood to most of the body’s organs.

Sometimes, plaque or cholesterol deposits stick in the inner wall of the artery. This causes the artery to become narrowed, a condition called renal artery stenosis.

Source: National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). NIH Publication No. 07–6020, May 2007

Image Credit: NIDDK Image Library

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This Page Last Revised: September 27, 2009

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Acquired cystic kidney disease, or ACKD, is a condition in which the kidneys develop fluid-filled sacs called renal (kidney) cysts. ACKD can occur in children and adults. The cysts are more likely to develop in people who have been on dialysis for many years. Dialysis, however, does not cause cysts to develop. ACKD is usually caused by kidney failure.

Most cases of cysts are harmless and do not require treatment. In some cases, infection in the cyst can occur. Sometimes the cysts bleed and blood will appear in the urine. Blood in the urine should always be reported to a doctor.

Causes of ACKD

Dialysis filters out many, but not all, of the wastes that healthy kidneys remove. Researchers believe that an unidentified waste product not removed through dialysis causes cysts to form in the kidneys. Dialysis itself does not cause the cysts.

Difference between polycystic kidney disease (PKD) and acquired cystic kidney disease (ACKD)

ACKD differs from PKD differs in many ways. People with PKD often have family history of PKD. In PKD, the kidneys enlarge and cysts also form in other parts of the body. ACKD, on the other hand, does not cause the kidneys to enlarge and cysts do not form in other parts of the body. In PKD, the presence of cysts marks the start of the disease. People with ACKD already have chronic kidney disease when cysts develop.

Symptoms of ACKD

ACKD often has no symptoms. However, when a cyst becomes infected, a person may have fever and back pain. A person may notice blood in the urine, which may indicate that there is bleeding in the cyst.

Diagnosis of ACKD

A doctor may suspect ACKD based on the patient’s history and symptoms. Imaging tests, such as ultrasound, computerized tomography (CT) scan, and magnetic resonance imaging (MRI) may be ordered by the doctor to confirm the diagnosis. In addition, images of the kidnes may help the doctor distinguish ACKD from PKD

Treatment of ACKD

No treatment is needed if ACKD is not causing discomfort or pain. Infections are treated with a course of antibiotics. If large cysts are causing pain, they may be drained using a long needle inserted through the skin.

If tumors are suspected, a person may need regular examinations to monitor the kidneys for cancer. Some doctors recommend all patients be screened for kidney cancer after 3 years of dialysis. In rare cases, surgery is used to stop cysts from bleeding and to remove tumors or suspected tumors.

In transplantation, the diseased kidneys are left in place unless they are causing infection or high blood pressure. ACKD usually disappears, even in the diseased kidneys, after a person receives a transplanted kidney.

Source: National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). NIH Publication No. 09–6403, May 2009

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Normally, urine contains water and wastes, such as urea, uric acid, creatinine, and some ions. However, some of these substances may be abnormally elevated, which usually indicates that something is wrong with the body.

The following are some of the abnormal constituents of urine and some possible causes.

Albumin

Albumin is a type of protein, which is a normal component of plasma—the fluid component of blood. When albumin is found to be excessive in the urine, it may indicate that the tiny filtering units in the kidney, called nephrons, are damaged or destroyed. Elevated albumin in the urine is termed albuminuria.

Bilrubin

Bilirubin, when modified by the kidneys, contributes to the classical yellow color of urine. It is a byproduct that results from the breakdown of hemoglobin—the red pigment in red blood cells. When levels of bilirubin in urine is above normal, the condition is called bilirubinuria. This may indicate liver disease or obstructive biliary disease.

Glucose

The presence of glucose or blood sugar in urine is called glucosuria. It may indicate that the person has diabetes.

Ketone bodies

The presence of ketone bodies in the urine may indicate diabetes or anorexia. It may also be elevated during fasting and starvation.

Microbes

The presence of microorganisms, such as bacteria or fungus may indicate urinary tract infection.

Blood

The red blood cells in blood should not be found in urine because they are too large to pass through the nephrons. Hematuria is the clinical term used when red blood cells are present in the urine. It may indicate damage to the kidney, such as in renal or kidney disease. Sometimes, blood may be present because of the presence of kidney stones.

White blood cells

When white blood cells are present in the urine, it may indicate infections in the kidney or other organs of the urinary tract.

Reference:

National Kidney and Urologic Diseases Information Clearinghouse. Your Urinary System and How It Works. National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. NIH Publication No. 07–3195, August 2007

Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.

Seeley, R. et al: ESSENTIALS OF ANATOMY AND PHYSIOLOGY. 5th ed. McGraw – Hill, 2005.

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What are the components of urine?

The body takes nutrients from food and uses them to maintain bodily functions including energy and self-repair. Once the body has taken what it needs from the food, waste products are produce. Adults can produce about a quart and a half of urine each day. The amount, however, may depend on many factors including the amount of fluid and food a person consumes and how much fluid is lost through breathing and sweating.

Urine contents:

In addition to water, other contents of urine include:

Urea

Urea is a substance produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body.

Bilirubin

This substance results from the breakdown of hemoglobin—the red pigment found in red blood cells. Bilirubin is modified in the kidneys and becomes a component of urine, which contributes to the yellow color of urine.

Creatinine

Creatinine is formed from the breakdown of creatine phosphate, which is a molecule found in muscle fibers.

Uric acid

Uric acid results from the breakdown of nucleic acids, which can be found in DNA (deoxyribonucleic acid).

Ions

Ions that are secreted in the urine include sodium, chloride, bicarbonate, potassium, and hydrogen ions. Sometimes, these ions will be transported back into the blood depending on the body’s needs.

Related Topic:
Abnormal Contents of Urine

Reference:

National Kidney and Urologic Diseases Information Clearinghouse. Your Urinary System and How It Works. National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. NIH Publication No. 07–3195, August 2007

Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.

Seeley, R. et al: ESSENTIALS OF ANATOMY AND PHYSIOLOGY. 5th ed. McGraw – Hill, 2005.
Marieb, E.: ESSENTIALS OF ANATOMY AND PHYSIOLOGY.

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A kidney stones diet can play a role in stopping stone formation. Other factors, such as family history, environment, fluid intake, and weight may also play a part in the formation of stones.

Normally, the body uses food for energy and also tissue repair. Once the body has used what it needs, waste products are carried to the kidneys to be excreted in the form of urine. Certain foods in the diet, however, create wastes that may form crystals in the urinary tract. These crystals can grow into stones in some people.

For people who have had a kidney stone, preventing the formation of another is a top priority. In addition to dietary changes by following a strict kidney stone diet, medications may also be needed to prevent formation. Learning about what kind of stones a person’s body typically makes is the first step in preventing kidney stone formation.

Types of Stones

The type of stones formed can be different from person to person. Types of kidney stones include the following:

 Calcium oxalate stones. This is the most common type. They usually form when the urine becomes too acidic, which means it has low pH. The body produces some of the oxalate found in urine. Calcium and oxalate obtained in the diet may play a role but are not the only factors that affect formation of calcium oxalate stones. Oxalate is found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in stone formation.

 Calcium phosphate stones. These stones are considered less common. Calcium phosphate stones are more likely to occur when the urine has high pH, meaning it is alkaline.

 Uric acid stones tend to form when the urine is persistently acidic. Uric acid stones may result from a diet high in animal protein and purines. Purines are substances found naturally in all food but especially in organ meats, fish, and shellfish.

 Struvite stones form as a result of infection in the kidey. Diet has not been shown to affect the formation of struvite stones. Preventing struvite stones depends on staying infection free.

 Cystine stones. This type of kidney stone results from a rare genetic disorder that causes cystine to leak through the kidneys and into the urine to form crystals. Cystine is an amino acid, which is one of the building blocks of protein.

Importance of knowing which type of stone a person has.

To determine why a certain patient is at risk of kidney stone formation, it greatly helps the doctor to know the chemical composition of the stone. The kind of stone typically a person’ body makes determines what dietary changes may be necessary. For example, limiting oxalate in the diet may help prevent formation of calcium oxalate stones but will not help in preventing uric acid stones.

Some recommendations in kidney stone diet may apply to more than one type of stone. Most notably, drinking enough water helps prevent all kinds of kidney stones.

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This Page Last Revised: May 20, 2010

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Following a strict kidney stones diet may prevent future stone formation. The following discusses about dietary changes you can make to help prevent kidney stones.

Dietary changes:

1. Drink lots of fluid.

Drinking lots of fluid help dilute the urine and help flush away materials that might form stones. The amount of fluid that a person needs to drink depends on the weather and the person’s activity level. According to the National Institutes of Health (NIH), people who have had a kidney stone should drink enough water and other fluids to produce at least 2 quarts of urine each day.

In addition to water intake, some drinks may also help in preventing stones. Some studies suggest citrus drinks, such as lemonade and orange juice protect against stones. These citrus drinks contain citrate, which stops crystals from growing into stone. Although citrus drinks may help prevent calcium oxalate stones and uric acid stones, they might be harmful for people who form calcium phosphate stones.

Coffee and tea have been shown to reduce the risk of stone formation. However, coffee and tea also contain oxalate. Moderate intake of beer and wine may also protect a person against stone formation.

Grapefruit juice and dark colas should be avoided by people who are prone to calcium oxalate stone formation. Cranberry juice is often promoted as helpful in preventing urinary tract infections, however, it contains oxalate and may be harmful to stone formers.

2. Limit salt intake.

The U.S. recommended daily allowance (RDA) of sodium is 2,400 milligrams (mg). Risk of kidney stone formation increases with increased daily sodium intake. Salt is made up of sodium and chloride. The sodium component of salt, when excreted by the kidneys causes more calcium to be excreted into the urine. High calcium concentrations in urine combine with either oxalate or phosphorus to form stones.

3. Limit animal protein intake.

Experts recommend that people who form uric acid stones should limit their meat intake to 6 ounces each day. Meats and other animal proteins, such as eggs and fish —contain purines, which break down into uric acid in the urine. Foods that are especially rich in purines include organ meats, such as liver.

Nondairy animal proteins may also increase the risk of calcium stones by increasing the excretion of calcium and reducing the excretion of citrate into the urine. Citrate prevents kidney stones, but the acid in animal protein reduces the citrate in urine.

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This Page Last Revised: May 20, 2010

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4. Dietary calcium

Calcium found in food does not increase a person’s risk of calcium oxalate stones. Calcium in the digestive tract prevents oxalate from entering the bloodstream into the kidneys by binding to oxalate. Experts recommend that people who form calcium oxalate should include 800 mg of calcium in their diet every day. This is not only to prevent formation of kidney stones but to maintain bone density as well.

5. Limit intake of foods high in oxalate

The body makes some of the oxalate found in urine. However, eating foods high in oxalate can increase the amount of oxalate in the urine. The high oxalate concentration in the urine can combine with calcium to form calcium oxalate stones.

Many foods and beverages contain oxalate, but only a few have been shown to increase the amount of oxalate in urine:

 spinach

 rhubarb

 nuts

 wheat bran

Avoiding these foods may help reduce the amount of oxalate in the urine. Eating foods containing calcium also reduces oxalate in the urine. Calcium binds oxalate in the digestive tract so it is not excreted into the urine.

6. Supplements

Supplements containing vitamin C or D may contribute to stone formation. Vitamin C is ascorbate and can be turned into oxalate by the body. Doctors recommend no more than 500 milligrams each day for people who have had kidney stones. Calcium supplements should be taken with meals so the calcium can bind with the oxalate in food. A person who has a tendency to form kidney stones should consult a doctor or dietitian before taking large doses of vitamins or minerals as part of their kidney stone diet.

7. Maintain a healthy weight

Studies have shown that being overweight increases the risk of kidney stones, particularly uric acid and calcium kidney stones. Scientists don’t know whether losing weight by itself can reduce the risk of kidney stones. Maintaining a healthy weight through healthy food choices and exercise may help reduce the risk of kidney stones

Reference: National Kidney and Urologic Diseases Information Clearinghouse. Diet for Kidney Stone Prevention. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH). NIH Publication No. 09–6425, May 2009

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Page Last Revised: November 14, 2009