Urinary Tract Infections

Urinary tract infections are mostly caused by ascending infection from the urethra into the bladder. The female urethra is short, and the external third harbors microorganisms (mostly bacteria) that normally exist in the vagina and colon. Bacteria travel up the urethra during urethral massage, sexual intercourse, or mechanical instrumentation (such as catheterization). Once in the bladder, some unique features of the bacteria play a major role in whether they will just colonize or infect the bladder.

Although UTIs are caused by many species of bacteria, most of them (80-90%) are caused by uropathogenic Escherichia coli (E.coli). Certain E. coli species are associated with infection that goes beyond the bladder and continues to ascend into the kidney. The remaining 10-20% of UTIs are caused by other bacteria that colonize (normally live in) the vagina and the area around the urethra.

Risk factors for UTI in women vary among different age groups. In young women, common risk factors include new onset of sexual activity and anatomic abnormalities they were born. Risk factors for premenopausal women include history of UTIs, holding urine for very long periods of time, frequent or recent sexual activity, diaphragm contraceptive use, use of spermicides, diabetes, obesity, anatomic abnormalities, urinary tract stones, and bladder catheterization. Finally, risk factors for postmenopausal women include vaginal atrophy (thinning), incomplete bladder emptying, poor hygiene, prolapse of the uterus, bladder, or rectum, diabetes, and a lifetime history of UTIs. Because of the lack of estrogen and vaginal atrophy in postmenopausal women, especially if accompanied by changes in hygiene, the rate of UTI increases with advancing age because these conditions make it easier for bacteria to flourish and ascend to the bladder via the urethra.

As mentioned, acute bacterial cystitis usually presents clinically as dysuria, with symptoms of frequent and urgent urination, secondary to irritation of the urethra and bladder lining. Women can also have pelvic pain above the pubic bone, and infrequently, hematuria (blood in the urine). Fever is uncommon in women with an uncomplicated UTI. Older women with a UTI may have may be asymptomatic, or only have urinary incontinence or hematuria or both. In contrast, an upper UTI, or acute pyelonephritis (kidney infection), commonly occurs with a combination of fever, chills, exquisite flank pain, and varying degrees of dysuria, urgency, and frequency.

Historically, the diagnosis of bacteriuria, as mentioned above, was made by finding 100,000 colonies of bacteria in a milliliter of urine. Now, it is accepted that bacteriuria can be diagnosed even when the bacterial colony count is 1,000-10,000 per milliliter urine in symptomatic women. However, just finding that many bacteria in the urine may not be enough to diagnose a UTI. Microscopic urinalysis can also reveal the presence of white blood cells in the urine, which really helps make the diagnosis. If a woman’s clinical presentation is very indicative of a UTI, a urine culture (done to see if and which bacteria grow out of the urine sample) need not be sent. But if the clinical presentation is in question, or if a woman with a presumed UTI is not improving after 48 hours of empiric therapy, a urine culture with an antibiotic sensitivity panel would help make the diagnosis of a UTI and indicate the appropriate specific antibiotic treatment, respectively.

Most recent data have shown that threee days of antibiotic therapy is the recommended therapy for uncomplicated bacterial cystitis in women, including women over age 65. Bacterial clearance rates are consistently higher than 90% after just three days of treatment. Ideally, laboratory urinanalysis should be done before antibiotic therapy is initiated to ensure the diagnosis of a UTI.

There are certain instances when women may be started on antibiotic therapy at the physician’s discretion based on their signs and symptoms without laboratory urinalysis (also known as empiric therapy). Empiric therapy is most appropriate for women with a history of recurrent UTIs and who are very aware of symptom onset. However, many women, especially postmenopausal women, can have symptoms of intermittent dysuria or urgent or frequent urination without a laboratory-proven UTI. Empiric therapy in these women leads to unnecessary antibiotic use and the development of antimicrobial resistance. Testing for white blood cells in the urine by laboratory urinalysis or by urinary dipstick in the office improves the likelihood of identifying infection and it’s best when either is done before antibiotic therapy is started.

In severe cases of recurrent UTIs, the first-line intervention for the prevention of the recurrence of cystitis is prophylactic or intermittent antibiotic therapy; recurrences are prevented in 95% of cases. However, there are multiple other non-medical and medical interventions that have been suggested. There is little evidence that aggressive hydration to prevent recurrences has any major effect. Likewise, post-intercourse voiding has not been proven effective, nor has douching. However, drinking cranberry juice or taking cranberry tablets decreases symptomatic UTIs. This is because cranberry prevents the attachment of urinary microorganisms to the bladder wall. Unfortunately, there is insufficient data to determine the optimal length of therapy and the concentration required to prevent recurrent UTIs long term.