URINARY TRACT INFECTIONS IN WOMEN

Tanya M. Nazemi, MD
Eastside Urology Associates (Kirkland, WA)

Infections of the urinary tract are a common occurrence, accounting for an estimated 7.3 million physician office visits annually.[i]  In addition, approximately 30% of women will have at least one symptomatic urinary tract infection (UTI) by the age of 24, and almost half of all women will have at least one UTI in their lifetime.1,[ii]  Once a patient has had an infection of the urinary tract, they are also likely to develop another infection in the future.

Most UTIs are caused by bacterial organisms that originate from the gastrointestinal tract and travel into the urinary tract via the urethra.  Certain bacteria tend to have more virulent characteristics that allow them to adhere to host vaginal and urothelial cells, thereby increasing the host’s risk for infection.  In addition, some women have receptors on the vaginal and urothelial cells that may cause them to be more susceptible to infections.[iii]  Infections of the urinary tract are most commonly caused by E.coli, which accounts for 85% of community-acquired and 50% of hospital-acquired infections.  Other bacteria including Proteus, Klebsiella, Enterococcus, andStaphylococcus are also common pathogens.2

Various risk factors have been associated with UTIs in women.  Women who are sexually active tend to have more frequent UTIs as intercourse can irritate the urethra and allow for bacteria to more easily enter the urinary tract.  Women who use diaphragms, spermicides, or unlubricated condoms may also have higher risks of infection.  In addition, any obstruction to the normal flow of urine can increase the ability of bacteria to colonize and multiply within the urinary tract.  Obstruction may occur from urethral strictures, stones in the bladder or urethra, urethral diverticula, prolapse of the bladder or urethra, or foreign bodies.  Women who have a compromised immune system may be more susceptible to infections as they are unable to adequately mount a defense against invading bacteria.  This may be seen in women with diabetes mellitus, chronic steroid use, women undergoing chemotherapy, or women with AIDS.  Postmenopausal women are particularly susceptible to recurrent UTIs.  The loss of estrogen alters the normal pH of the vagina which causes tissues to weaken and become irritated.  In addition to this, pH changes cause loss of normal vaginal bacteria such as lactobacillus, which generally limits the growth of pathogenic bacteria.[iv]

Women with UTIs may present with various signs and symptoms.  Most will usually develop pain with urination, urgency, frequency, strong odor to the urine, cloudy urine, or blood in the urine (hematuria).  In addition, some women may develop incontinence, fevers, flank pain, or suprapubic pain.  Flank pain, fever, chills, nausea, and vomiting are signs of a more complicated infection of the kidneys, also known as pyelonephritis, which often requires intravenous antibiotics and hydration.

A presumptive diagnosis of UTI may be made with a urine dipstick which can quickly assess for the presence of bacteria, white blood cells, red blood cells, and nitrites (a bacterial breakdown product).  Infection is later confirmed by culture of the urine to appropriately identify the causative pathogen.  If patients have recurrent culture-proven infections with certain bacteria such as Proteus, imaging studies such as CT or ultrasound may be used to rule out any anatomic abnormalities or stones that may be acting as a nidus for the persistent infections.  Similarly, patients with recurrent infections and a history of hematuria may also be evaluated with imaging studies and cystoscopy, in which a small scope is passed into the urinary tract to assess the bladder and rule out any foreign bodies or other abnormalities.

Most uncomplicated urinary tract infections may be treated with a short course of antibiotics.  The most commonly used antibiotics are filtered through the kidneys and concentrate in the urine.  These include penicillins (Ampicillin), cephalosporins (Cephalexin), trimethoprim-sulfamethoxazole (Bactrim), nitrofurantoin (Macrobid, Macrodantin, Furadantin), and quinolones (Levofloxacin, Ciprofloxacin, Norfloxacin).  Other antimicrobials that may be used include aminoglycocides (Gentamicin, Kanamycin) tetracylcines, and vancomycin, although these are less common.  The choice of which antibiotic to use depends on the severity of the infection, patient comorbidities, renal function, patient allergy, side effects, and bacterial pathogen.  Generally, trimethoprim-sulfamethoxazole (TMP-SMX) has been the most commonly used antibiotic for the treatment of uncomplicated UTIs.  It is inexpensive and covers many urinary pathogens, although patients may develop skin irritation and gastrointestinal upset.  Nitrofurantoin is also very effective against most common bacterial infections of the urinary tract and generally has less GI side effects.  It is not as effective for more complicated infections or infections in the kidney.  However, bacterial resistance to nitrofurantoin is low and the medication is generally well tolerated and often used effectively for prophylaxis against recurrent infections.  The quinolones are a group of broad spectrum antibiotics that are highly effective in killing the majority of urinary pathogens.  Unfortunately, bacterial resistance to quinolones as well as TMP-SMX has been rising due to indiscriminate use of these medications.  The duration of therapy is generally 3-5 days but may be longer based on the severity of the infection.

Women with UTIs may take steps to help prevent recurrent infections.  Simple measures include drinking plenty of water, urinating frequently (which does not allow for bacteria to colonize in the urinary tract), wiping from front to back, voiding immediately following intercourse, and avoiding use of feminine hygiene sprays and scented douches.  Some studies have found that drinking cranberry juice may have a protective effect against recurrent UTIs as well.[v],[vi]  For women who have repeated infections associated with sexual intercourse, a course of continuous antibiotic prophylaxis for 6-12 months or single dose antibiotics following intercourse may reduce the rate of UTIs.[vii]  For women who are postmenopausal, local estrogen replacement with vaginal tablets, creams, or ring (Vagifem®, Estrace®, Estring®) frequently restores the normal vaginal environment, allows recolonization with lactobacilli, and decreases pathogenic bacterial colonization, thus reducing UTIs.4,[viii]

UTIs are common and troublesome infections that affect millions of women each year.  Preventative measures may be taken, however, early diagnosis and initiation of appropriate antibiotic therapy is often effective.

 


[i] Foxman B, Barlow R, D’Arcy H, Gillespie B, Sobel JD. Urinary tract infection: self-reported incidence and associated costs. Ann Epidemiol. 2000;10:509-515.

[ii] Wein, A., Kavoussi, L., Novick, A. Partin, A, Peters, C. eds.: Campbell-Walsh Urology, 9th ed: Elsevier, pp.221-301

[iii] Wright KJ, Hultgren SJ. Sticky fibers and uropathogenesis: bacterial adhesins in the urinary tract. Future Microbiol. 2006 Jun;1:75-87.

[iv] Kelley C. Estrogen and its effect on vaginal atrophy in post-menopausal women. Urol Nurs. 2007 Feb;27(1):40-5.

[v] Howell AB. Bioactive compounds in cranberries and their role in prevention of urinary tract infections. Mol Nutr Food Res. 2007 Jun;51(6):732-7.

[vi] Jepson RG, Craig JC. A systematic review of the evidence for cranberries and blueberries in UTI prevention. Mol Nutr Food Res. 2007 Jun;51(6):738-45.

[vii] Albert X, Huertas I, Pereiro II, Sanfelix J, Gosalbes V, Perrota C. Antibiotics for preventing recurrent urinary tract infection in non-pregnant women.Cochrane Database Syst Rev. 2004;(3):CD001209.

[viii] Raz R, Stamm WE: A controlled trial of intravaginal estriol in postmenopausal women with recurrent urinary tract infections. N Engl J Med 1993;329:753-756.

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