Urinary tract infections
Cystitis is defined as inflammation of the urinary bladder. Urethritis is aninflammation of the urethra, which is the passageway that connects the bladder with the exterior of the body. Sometimes cystitis and urethritis are referred to collectively as a lower urinary tract infection, or UTI. Infection of the upper urinary tract involves the spread of bacteria to the kidney and is called pyelonephritis.
The frequency of bladder infections in humans varies significantly accordingto age and sex. The male/female ratio of UTIs in children younger than 12 months is 4:1 because of the high rate of birth defects in the urinary tract ofmale infants. In adult life, the male/female ratio of UTIs is 1:50. After age50, however, the incidence among males increases due to prostate disorders.
Cystitis is a common female problem. It is estimated that 50% of adult womenexperience at least one episode of dysuria (painful urination); half of thesepatients have a bacterial UTI. Between 2-5% of women's visits to primary care doctors are for UTI symptoms. About 90% of UTIs in women are uncomplicatedbut recurrent.
UTIs are uncommon in younger and middle-aged men, but may occur as complications of bacterial infections of the kidney or prostate gland.
In children, cystitis is often caused by congenital abnormalities (present atbirth) of the urinary tract. Vesicoureteral reflux is a condition in which the child cannot completely empty the bladder. It allows urine to remain in orflow backward (reflux) into the partially empty bladder.
The causes of cystitis vary according to sex because of the differences in anatomical structure of the urinary tract.
Most bladder infections in women are so-called ascending infections, which means that they are caused by disease agents traveling upward through the urethra to the bladder. The relative shortness of the female urethra (1.2-2 inchesin length) makes it easy for bacteria to gain entry to the bladder and multiply. The most common bacteria associated with UTIs in women include Escherichia coli (about 80% of cases), Staphylococcus saprophyticus, Klebsiella, Enterobacter, and Proteus species. Risk factorsfor UTIs in women include:
- Sexual intercourse. The risk of infectionincreases if the woman has multiple partners.
- Use of a diaphragm forcontraception
- An abnormally short urethra
- Diabetes or chronic dehydration
- The absence of a specific enzyme (fucosyltransferase) in vaginal secretions. The lack of this enzyme makes it easier for the vagina to harbor bacteria that cause UTIs.
- Inadequate personal hygiene.Bacteria from fecal matter or vaginal discharges can enter the female urethrabecause its opening is very close to the vagina and anus.
- History of previous UTIs. About 80% of women with cystitis develop recurrences withintwo years.
The early symptoms of cystitis in women are dysuria, or pain on urination; urgency, or a sudden strong desire to urinate; and increased frequency of urination. About 50% of female patients experience fever, pain in the lower back or flanks, nausea and vomiting, or shaking chills. These symptoms indicate pyelonephritis, or spread of the infection to the upper urinary tract.
Most UTIs in adult males are complications of kidney or prostate infections.They are usually associated with a tumor or kidney stones that block the flowof urine and are often persistent infections caused by drug-resistant organisms. UTIs in men are most likely to be caused by E. coli or another gram-negative bacterium. S. saprophyticus, which is the second most common cause of UTIs in women, rarely causes infections in men. Risk factors forUTIs in men include:
- Lack of circumcision. The foreskin can harbor bacteria that cause UTIs.
- Urinary catheterization. The longer the period of catheterization, the higher the risk of UTIs.
The symptoms of cystitis and pyelonephritis in men are the same as in women.
Hemorrhagic cystitis, which is marked by large quantities of blood in the urine, is caused by an acute bacterial infection of the bladder. In some cases,hemorrhagic cystitis is a side effect of radiation therapy or treatment withcyclophosphamide. Hemorrhagic cystitis in children is associated with adenovirus type 11.
When cystitis is suspected, the doctor will first examine the patient's abdomen and lower back, to evaluate unusual enlargements of the kidneys or swelling of the bladder. In small children, the doctor will check for fever, abdominal masses, and a swollen bladder.
The next step in diagnosis is collection of a urine sample. The procedure differs somewhat for women and men. Laboratory testing of urine samples can nowbe performed with dipsticks that indicate immune system responses to infection, as well as with microscopic analysis of samples. Normal human urine is sterile. The presence of bacteria or pus in the urine usually indicates infection. The presence of hematuria, or blood in the urine, may indicate acute UTIs,kidney disease, kidney stones, inflammation of the prostate (in men), endometriosis (in women), or cancer of the urinary tract. In some cases, blood in the urine results from athletic training, particularly in runners.
Female patients require a pelvic examination as part of the procedure to obtain urine specimens. The patient lies on an obstetrical table with legs in thestirrups. The doctor first takes a vaginal culture smear. The patient is then asked to void while lying on the table. The first five to 10 ml are collected to test for urethral infection. A midstream urine sample of 200 ml is thencollected to test for bladder infection.
In women, a vaginal bacterial count that is higher than those of the two urine samples indicates vaginitis. A high bacterial count in the first urine sample indicates urethritis. A count of more than 104 bacteria CFU/ml (colony forming units per milliliter) in the midstream sample indicates a bladder or kidney infection. A colony is a large number of microorganisms that grow from asingle cell within a substance called a culture. Bacterial count can be givenin CFU or colony forming units.
In male patients, the doctor will cleanse the opening to the urethra with anantiseptic before collecting the urine sample. The first 10 ml of specimen are collected separately. The patient then voids a midstream sample of 200 ml.Following the second sample, the doctor will massage the patient's prostate and collect several drops of prostatic fluid. The patient then voids a third urine specimen for prostatic culture.
A high bacterial count in the first urine specimen or the prostatic specimensindicates urethritis or prostate infections respectively. A bacterial countgreater than 100,000 bacteria CFU/ml in the midstream sample suggests a bladder or kidney infection.
Women with recurrent UTIs can be given ultrasound tests of the kidneys and bladder together with a voiding cystourethrogram to test for structural abnormalities. (A cystourethrogram is an x-ray test in which an iodine dye is used to better view the urinary bladder and urethra.) Voiding cystourethrograms arealso used to evaluate children with UTIs. In some cases, computed tomographyscans (CT scans) can be used to evaluate patients for possible cancers in the urinary tract.
Uncomplicated cystitis is treated with antibiotics. These include penicillin,ampicillin, and amoxicillin; sulfisoxazole or sulfamethoxazole; trimethoprim; nitrofurantoin; cephalosporins; or fluoroquinolones. (Flouroquinolones aregenerally not used in children under 18 years of age.) Treatment for women isshort-term; most patients respond within three days. Men do not respond as well to short-term treatment and require seven to 10 days of oral antibioticsfor uncomplicated UTIs.
Patients of either sex may be given phenazopyridine or flavoxate to relieve painful urination.
Trimethoprim and nitrofurantoin are preferred for treating recurrent UTIs inwomen.
Over 50% of older men with UTIs also suffer from infection of the prostate gland. Some antibiotics, including amoxicillin and the cephalosporins, do not affect the prostate gland. Fluoroquinolone antibiotics or trimethoprim are thedrugs of choice for these patients.
Patients with pyelonephritis can be treated with oral antibiotics or intramuscular doses of cephalosporins. Medications are given for 10-14 days, and sometimes longer. If the patient requires hospitalization because of high fever and dehydration caused by vomiting, antibiotics can be given intravenously.
A minority of women with complicated UTIs may require surgical treatment to prevent recurrent infections. Surgery is also used to treat reflux problems (movement of the urine backwards) or other structural abnormalities in childrenand anatomical abnormalities in adult males.
The prognosis for recovery from uncomplicated UTIs is excellent; however, complicated UTIs in males are difficult to treat because they often involve bacteria that are resistant to commonly used antibiotics.
Women with two or more UTIs within a six-month period are sometimes given prophylactic treatment, usually nitrofurantoin or trimethoprim for three to sixmonths. In some cases the patient is advised to take an antibiotic tablet following sexual intercourse.
Other preventive measures for women include:
- Drinking large amounts offluid
- Voiding frequently, particularly after intercourse
- Proper cleansing of the area around the urethra.
The primary preventive measure for males is prompt treatment of prostate infections. Chronic prostatitis may go unnoticed but can trigger recurrent UTIs.In addition, males who require temporary catheterization following surgery can be given antibiotics to lower the risk of UTIs.