The Urinary System

The organs, tubes, muscles and nerves that work together to create, store and carry urine are the urinary system. The urinary system includes two kidneys, two ureters, the bladder, two sphincter muscles and the urethra.

Your urinary system works to excrete waste products from your body and to keep the chemicals and water in your body balanced. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says adults eliminate about a quart and a half of urine each day. The amount depends on many factors, including how much you eat and drink and how much fluid is lost through sweat (Read about "Sweating") and breathing. Certain types of medications can also affect the amount of urine eliminated.

The urinary system removes a type of waste called urea from your blood. Urea is produced when foods containing protein are broken down in the body. Urea is carried in the bloodstream to the kidneys. The kidneys remove urea from the blood through tiny filtering units called nephrons. From the kidneys, urine travels down two thin tubes called ureters to the bladder. The bladder is a hollow muscular organ in your pelvis. It stores urine until you are ready to go to the bathroom to empty it. The urethra is the tube that lets urine pass outside the body. Nerves (Read about "Nervous System") in the bladder let you know when it is time to do this. Until then, muscles called sphincters help keep urine from leaking by closing tightly around the opening of the bladder into the urethra.

Diseases and conditions

Problems in the urinary system can be caused by aging, illness or injury. As you get older, changes in the kidneys' structure cause them to lose some of their ability to remove wastes from the blood. Also, the muscles in your ureters, bladder, and urethra tend to lose some of their strength as you age.

Urologists are doctors who treat diseases and conditions of the urinary system in both men and women, as well as the male reproductive system. (Read about "Genital Health - Male" "Reproductive Health") Urological diseases and conditions include:

• Interstitial cystitis (IC) - Interstitial cystitis or IC is also known as painful bladder syndrome or frequency-urgency-dysuria syndrome. It is a chronic bladder disorder. In this disorder, the bladder wall can become inflamed and irritated. (Read about "Interstitial Cystitis")
• Kidney stones - Kidney stones is the term commonly used to refer to stones, or calculi, in the urinary system. Stones form in the kidneys and may be found anywhere in the urinary system. They vary in both size and the amount of pain that they cause. (Read about "Kidney Stones")
• Proteinuria - Proteinuria is the presence of abnormal amounts of protein in the urine. Healthy kidneys take wastes out of the blood but leave in protein. Protein in the urine does not cause a problem by itself. But it may be a sign that your kidneys are not working properly, although a small amount of protein in the urine can be a normal variation.
• Renal failure/kidney failure - Renal (kidney) failure results when the kidneys are not able to regulate water and chemicals in the body or remove waste products from your blood. Acute renal failure (ARF) is the sudden onset of kidney failure. This condition can be caused by an accident that injures the kidneys, significant blood loss, or some drugs or poisons. ARF may lead to permanent loss of kidney function. But if the kidneys are not seriously damaged, they may recover. Chronic kidney disease (CKD) is the gradual reduction of kidney function that may lead to permanent kidney failure, or end-stage renal disease (ESRD). You may go several years without knowing you have CKD. (Read about kidney failure in "Kidney Disease" "End Stage Renal Disease")
• Urinary tract infections (UTI) - Urinary tract infections (UTI) are caused by bacteria (Read about "Microorganisms") in the urinary tract. Women get UTIs more often than men. Children can get them as well. UTI's are treated with antibiotics. (Read about "Antibiotics") Drinking lots of fluids also helps by flushing out the bacteria. The name of the UTI depends on its location in the urinary tract. An infection in the bladder is called cystitis. If the infection is in one or both of the kidneys, the infection is called pyelonephritis. This type of UTI can cause serious damage to the kidneys if it is not adequately treated. (Read about "Urinary Tract Infections")
• Incontinence - Urinary incontinence, or loss of bladder control, is the involuntary passage of urine. There are many causes and types of incontinence, and many treatment options. Treatments range from simple exercises to surgery. Women are affected by urinary incontinence more often than men. Children may be affected as well. (Read about "Incontinence")
• Overactive bladder (OAB) - Overactive bladder is a condition in which the bladder squeezes too often or squeezes without warning. Symptoms include leaking urine (urinary incontinence), feeling the sudden and urgent need to urinate, and frequent urination. The Food and Drug Administration (FDA) says overactive bladder affects an estimated 33 million Americans, the majority of whom are older women. According to NIDDK, voiding up to seven times a day is normal for many women, but women with overactive bladder may find that they must urinate even more frequently.
• Urinary retention - Urinary retention, or bladder-emptying problems, is a common urological problem with many possible causes. Normally, urination can be initiated voluntarily and the bladder empties completely. Urinary retention is the abnormal holding of urine in the bladder. Acute urinary retention is the sudden inability to urinate, causing pain and discomfort. Causes can include an obstruction in the urinary system, stress or neurologic problems. (Read about "Stress" "Nervous System") Chronic urinary retention refers to the persistent presence of urine left in the bladder after incomplete emptying. Common causes of chronic urinary retention are bladder muscle failure, nerve damage or obstructions in the urinary tract. Treatment for urinary retention depends on the cause.
• Cystocele - A cystocele occurs when the wall between a woman's bladder and her vagina weakens and allows the bladder to droop into the vagina. This condition may cause discomfort and problems with emptying the bladder. It can also cause unwanted urine leakage. (Read about "Incontinence") A cystocele may result from muscle straining while giving birth. (Read about "Childbirth") Other kinds of straining - such as heavy lifting or repeated straining during bowel movements - may also cause the bladder to fall. Women are also more at risk after menopause. (Read about "Menopause") If a cystocele is not causing problems, a doctor may only recommend avoiding heavy lifting or straining that could cause it to worsen. If symptoms are moderate, the doctor may recommend a pessar - a device placed in the vagina to hold the bladder in place. Pessaries come in a variety of shapes and sizes and should be removed regularly to avoid infection or ulcers. Large cystoceles may require surgery to move the bladder back into a more normal position and keep it there. (Read about "Pelvic Floor Disorders")
• Nephrotic syndrome - Nephrotic syndrome is a condition marked by very high levels of protein in the urine (proteinuria), low levels of protein in the blood, swelling, especially around the eyes, feet and hands and high cholesterol. Nephrotic syndrome results from damage to the kidneys' glomeruli, the tiny blood vessels that filter waste and excess water from the blood and send them to the bladder as urine. It can be caused by any of a group of diseases that damage the kidneys. Treatment of nephrotic syndrome often focuses on identifying the underlying cause if possible and reducing high cholesterol, blood pressure and protein in urine through diet, medications or both. (Read about "Cholesterol" "Hypertension: High Blood Pressure")
• Cancer - Urological cancer can also develop, most commonly in the bladder and in the kidneys in men and women, and in the prostate or testicles in men. Symptoms are similar to those of other urinary tract problems, and can include blood in the urine, frequent urination, painful urination and pain in the lower back. (Read about "Kidney Cancer" "Bladder Cancer" "The Prostate" "Testicular Cancer" "Urethral Cancer")
• Benign prostatic hyperplasia (BPH) - Benign prostatic hyperplasia (BPH) is a condition in men that affects the prostate gland, which is part of the male reproductive system. BPH is an enlargement of the prostate gland that can interfere with urinary function in older men. (Read about BPH in "The Prostate")
• Prostatitis - Prostatitis is inflammation of the prostate gland that results in urinary frequency and urgency, burning or painful urination, a condition called dysuria, and pain in the lower back and genital area, among other symptoms. (Read about prostatitis in "The Prostate")
• Male reproductive conditions - Other diseases and conditions affecting the male reproductive organs, and thus treatable by a urologist, include erectile dysfunction or ED (Read about "Erectile Dysfunction"), infertility (Read about "Infertility"), STD's (Read about "STD's"), and hernia (Read about "Hernia"), as well as epididymitis, hydrocele, hypospadias, meatal stenosis, orchitis, paraphimosis, Peyronie's disease, priapism, undescended testicle, varicocele. (Read about these and other conditions in "Genital Health - Male" "Reproductive Health")
• Birth Defects - The March of Dimes (MOD) calls genitourinary defects common, affecting as many as 1 in 10 babies. (Read about "Birth Defects") Some of these abnormalities are minor and cause no symptoms. Others can cause pain, urinary tract infections and kidney disease. (Read about "Genitourinary Birth Defects")

Testing

Urinalysis is a test that studies the content of urine for abnormal substances such as protein or signs of infection. This test involves urinating into a special container and leaving the sample to be studied. Protein is a major building block that our body uses to build muscle. Normally the kidneys leave protein in the blood. If protein shows up in your urine (proteinuria), it may indicate problems with the kidneys. Your glomerular filtration rate (GFR) is a measure of how well your kidneys are filtering wastes from your blood. Your GFR can be estimated from a routine measurement of creatinine in your blood.

Urodynamic tests evaluate the storage of urine in the bladder and the flow of urine from the bladder through the urethra. Your doctor may want to do a urodynamic test if you are having symptoms that suggest problems with the muscles or nerves of your lower urinary system and pelvis - ureters, bladder, urethra and sphincter muscles. Urodynamic tests measure the contraction of the bladder muscle as it fills and empties. The test is done by inserting a small tube called a catheter through your urethra into your bladder to fill it either with water or a gas. Another small tube is inserted into your rectum or vagina to measure the pressure put on your bladder when you strain or cough.

Renal imaging procedures can also be used. X-rays (Read about "X-rays") of the urinary tract can help highlight a kidney stone or tumor that could block the flow of urine and cause pain. An x-ray can also show the size and shape of the prostate. X-rays can also be combined with contrast material. For example, in intravenous pyelogram (IVP), a contrast medium is injected into a vein, and followed as it circulates through the blood and reaches the kidneys. In voiding cystourethrogram (VCUG), a catheter inserted in the urethra is used to fill the bladder with a contrast medium, which can then be watched on video during urination. Other imaging tests such as ultrasound, CT scan or magnetic resonance imaging (Read about "Ultrasound Imaging" "CT Scan - Computerized Tomography" "MRI - Magnetic Resonance Imaging"), are also used.