A urinary tract infection is an infection involving the organs that produce urine and carry it out of the body. These structures include the kidneys, ureters (long, slender tubes connecting the kidneys with the bladder), bladder and urethra. Doctors often divide urinary tract infections into two types, lower tract infections and upper tract infections:
- Lower tract infections. Infection of the bladder is called cystitis (bladder infection). Bacteria normally found in the intestine are the main cause of lower urinary tract infections. These bacteria spread from the anus to the urethra and bladder, where they grow, invade the tissue and cause infection.
- Upper tract infections. These involve the ureters and kidneys. These infections are called pyelonephritis or kidney infections. Upper urinary tract infections usually occur because bacteria travel up from the bladder into the kidney. Sometimes, they occur when bacteria travel from other areas of the body through the bloodstream and settle in the kidney.
Women are affected much more often than men because women have short urethras that allow relatively easy passage of bacteria into the bladder. Sexual intercourse can cause bacteria to spread upward into the bladder. Also, the use of contraceptive diaphragms and spermicides may change the normal bacterial environment around the urethra and make infection more likely. In pregnant women, temporary changes in the physiology and anatomy of the urinary tract make expectant mothers prime candidates for cystitis and pyelonephritis. Kidney and bladder infections can pose a serious risk to pregnant women and their unborn children, because they increase the risk of premature contractions or delivery and sometimes death of the fetus or newborn infant.
Lower and upper tract infections can cause one or more of the following symptoms:
- Unusually frequent urination
- An intense urge to urinate
- Pain, discomfort or a burning sensation during urination
- Pain, pressure or tenderness in the area of the bladder (midline, above or near the pubic area)
- Urine that looks cloudy, or smells foul or unusually strong
- Fever, with or without chills
- Nausea and vomiting
- Pain in the side or mid-to-upper back
- Waking from sleep to pass urine
- Bedwetting in a person who has usually been dry at night
Your doctor will ask you about your symptoms and whether you have had a urinary tract infection before. He or she also will ask you about your sexual history, including any history of sexually transmitted diseases for yourself and your partner, condom use, multiple partners, use of diaphragm and/or spermicides and whether you could be pregnant. Your doctor also will ask if you have any other medical problems, such as diabetes, which can make you more likely to develop infections.
You will be asked to give a urine sample, which will be tested in a laboratory to see if it contains bacteria or other signs of infection. Your urine sample also may be sent to the laboratory to identify the specific type of bacteria and the specific antibiotics that can be used to eliminate the bacteria. If you have a fever or other symptoms of an upper tract infection, your doctor may order a blood test to determine your white blood cell count. A high white cell count indicates infection. The blood can also be tested for bacterial growth. This is called a blood culture.
In people with symptoms of a severe kidney infection or frequent episodes of lower or upper urinary tract infections, additional testing may be needed, such as:
- A computed tomography (CT) scan of your kidneys and urinary system
- An ultrasound exam
- Cystoscopy, an examination in which your doctor checks the inside of your bladder using a thin, hollow telescope-like instrument.
With proper treatment, most uncomplicated urinary tract infections can be cured in two to three days. It may take several days for the symptoms of a kidney infection to completely go away.
To help prevent urinary tract infections:
- Drink several glasses of water each day. Fluids discourage the growth of bacteria by flushing out your urinary tract. Drinking cranberry juice may deter bacterial growth by decreasing the ability of bacteria to stick to the urethra.
- Wipe from front to back. To prevent the spread of intestinal bacteria from the rectum to the urinary tract, women always should wipe toilet tissue from front to the back after having a bowel movement.
- Decrease the spread of bacteria during sex. Urinate after sexual intercourse to flush bacteria from your urethra. If you keep getting infections, you should talk to your doctor about using antibiotics after sex to lower the risk of developing urinary tract infections.
Doctors treat lower and upper urinary tract infections with antibiotics. Laboratory testing can determine the best antibiotic for treatment. Most uncomplicated lower tract infections are treated with a three-day course of antibiotics, although women who are pregnant, or who have diseases such as diabetes that suppress the immune system, usually need to take antibiotics for longer.
People with upper tract infections are usually treated with a 10- to 14-day course of antibiotic therapy. Those with severe upper tract infections may require hospital treatment with antibiotics given through a vein (intravenously). This is especially true if nausea, vomiting and fever increase the risk of dehydration and prevent the person from taking oral antibiotics.
Call your doctor if you have frequent urination, an intense urge to urinate, discomfort during urination or other symptoms of a urinary tract infection. You also should seek medical attention if you have symptoms of a kidney infection, such as fever, nausea, vomiting and pain in the side or back. It is especially important for any pregnant woman who has symptoms of an upper or lower urinary tract infection to call her doctor immediately.
Once a woman has been cured of cystitis, she has a 20% chance of developing a second infection. After the second infection, she has a 30% risk of developing a third. If a woman has three or more episodes of cystitis within 1 year and the structure or anatomy of the urinary tract is normal, her doctor may prescribe a special antibiotic regimen to decrease the risk of future infections.
National Institute of Diabetes & Digestive & Kidney Disorders
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American Foundation for Urologic Disease
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