Urinary Tract Infections in Women
Section snippets
Epidemiology
The evaluation and treatment of community-acquired UTI commands a significant portion of health care resources. UTI is the chief complaint in eight million clinic and emergency department visits, leading to approximately 100,000 hospital admissions each year. Antimicrobial agents used for the treatment of UTI account for 15% of all outpatient prescriptions. The annual health care cost is an estimated $1.6 billion dollars and rising.1 Women shoulder the greatest burden of disease, with a greater
Susceptibility factors
Increased female susceptibility to urinary tract infection is a function of basic anatomic factors as well as behavioral and physiologic factors that evolve over a woman’s lifetime. The short female urethra provides an ideal bridge for invading pathogens and rapid ingress to the bladder. The longer male urethra facilitates urinary washout of ascending bacteria before entry to the bladder is permitted and is perhaps the most significant protective factor against infection in men. The proximity
Behavioral factors
Behavioral factors help microbes capitalize on female anatomic vulnerability. Several studies have found a dose-dependent relationship between sexual intercourse and the risk of UTI, findings which are corroborated by the spike in first infections among young adult women around the time of first sexual activity.10 A prospective study of 796 sexually active young women found that the relative risk of UTI for sexual intercourse on 1, 3, and 5 of the previous 7 days was 1.42, 2.83, and 5.68,
Genetic factors
Genetic predisposition to recurrent UTI is a well-supported concept, and women who suffer from recurrent infections often note maternal or other family history of infection. Schaeffer and colleagues19 observed that women with recurrent UTI exhibit increased E coli binding receptivity that is not limited to the vaginal and urethral mucosa but also includes buccal mucosa, suggesting genetic differences in mucosal properties rather than differences in local milieu. Lewis blood group antigen
Age-specific factors
Estrogen status is perhaps the most important age-specific risk determinant for UTI. Estrogen promotes acidic vaginal pH and lactobacillus proliferation, which are the greatest host defenses against pathogenic colonization. Withdrawal of estrogen at the time of menopause leads to conversion of the predominant vaginal flora from lactobacillus to E coli and other Enterobacteriaceae, thus increasing the incidence of infection. A randomized, double-blind placebo-controlled trial of intravaginal
Urinary catheterization
Indwelling urinary catheters and clean intermittent catheterization (CIC) are associated with high rates of bacteriuria. The incidence of bacteriuria is 3% to 6% per day with indwelling catheters and 1% to 3% per catheterization with CIC; thus virtually all patients using these modalities will have bacteriuria after 1 month.30, 31 Tambyah and colleagues32 found that among patients with short-term indwelling catheters (ie, 2 to 4 days) placed during acute care admissions, the incidence of fever
Pregnancy
Pregnancy is an independent risk factor of upper UTI. While the incidence of asymptomatic bacteriuria is virtually identical in pregnant and nonpregnant women of child-bearing age (2% to 7%), pregnancy-induced physiologic changes in the urinary tract increase the likelihood of upper UTI. Progesterone induces tonic relaxation of the ureteric smooth muscle, while blood volume and glomerular filtration rate (GFR) increase markedly to support the growing fetus, creating a permissive environment for
Pathogenesis
Most upper and lower UTIs result from bacterial ascent from the bowel or vaginal mucosa. The most common infecting pathogens are resident facultative anaerobes and gram-negative bacteria from the bowel and vaginal flora. E coli is the causative organism in nearly 85% of UTIs, Staphylococcus saphrophyticus represents 10% to 15% of cases, and Enterobacteriaceae species, Proteus, and Klebsiella comprise the remaining minority.4
E coli causes the greatest proportion of disease because of its
Urinalysis and Urine Culture
Urinalysis is an array of biochemical assays and microscopic evaluations designed to aid in the presumptive diagnosis of UTI by facilitating the rapid identification of bacteriuria and pyuria. It is the most commonly used diagnostic modality in the outpatient evaluation of suspected UTI. Leukocyte esterase and nitrite are the most commonly referenced, and perhaps the most useful indices from the urine dipstick screening assay. The presence of leukocyte esterase suggests pyuria, indicative of
Initial and Isolated Cystitis
The most common presenting symptoms for uncomplicated cystitis are urinary frequency, urgency, and dysuria. In a healthy patient presenting with initial or isolated clinical UTI (ie, no previous UTI in ≥1 year) it can be treated empirically on the basis of symptoms and positive urinalysis, provided that complicating factors have been thoroughly explored and excluded by history, physical examination, or imaging or ancillary tests as indicated. The clinical history is the physician’s best first
Red flags
It is important to remain cognizant of several clinical scenarios in which classic signs and symptoms of cystitis belie a more complex underlying process:
Gross hematuria or persistent microscopic hematuria between documented infections should heighten the index of suspicion for underlying malignancy. Formal urologic evaluation should be pursued, including cystoscopy, urine cytology, and triphasic CT scan or renal ultrasound and retrograde pyelogram.
Recurrent symptoms of cystitis in the setting
Treatment
Optimal antimicrobial agents for uncomplicated UTI are frequently in flux because of rapidly evolving antibiotic resistance patterns. The core principals of therapy for UTI, however, do not change. Timely administration of an agent that exhibits the appropriate spectrum of activity against the known or most likely infecting pathogen, with dose and therapy duration that are sufficient to affect bacterial eradication while minimizing the risk of adverse effects and the growth of resistant
Duration of therapy
Optimal antimicrobial therapy duration has been a well studied topic in the literature. The 3-day treatment regimen is widely advocated for the treatment of uncomplicated cystitis because of its excellent balance of effective symptom and pathogen eradication with minimal alterations in vaginal and bowel flora or adverse drug effects. A 2005 Cochrane review of randomized controlled trials comparing 3 days of oral antibiotic therapy with multiday therapy (5 days and longer) for uncomplicated
Nitrofurantoin
With the incidence of uropathogen resistance rapidly exceeding 20% for trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim, Septra) in many regions of the United States, nitrofurantoin (Macrobid, Macrodantin, Furodantin) has re-emerged on the clinical radar as viable first-line therapy for uncomplicated cystitis. The national rate of resistance is 0% to 7% throughout the literature, despite nitrofurantoin having been developed more than 50 years ago and being one of the first effective oral
Monitoring antimicrobial resistance
Given the rapid rate at which antimicrobial resistance patterns are evolving, staying abreast of local patterns requires engagement with the literature and vigilance in one’s own practice. It is a good practice to review one’s outpatient urine culture results on a monthly or quarterly basis for trends in resistance in the immediate community.
Antimicrobial prophylaxis
For recurrent urinary tract infections, three antimicrobial regimens can effectively reduce the number and frequency of symptomatic infections. Continuous, symptom-dependent, and behavior-dependent prophylaxis schemes exist and confer similar risk reduction. Selection of an appropriate regimen is based largely upon patient lifestyle and compliance and patterns of infection.
Summary
Nearly half of the world’s women will experience a symptomatic UTI in their lifetime, and up to one-third of those affected will be plagued by recurrent infections. The management of UTI can be a formidable task given the prevalence of disease and high rate of recurrence, wide range of associated morbidity, rapidly evolving antimicrobial resistance and limited complement of antimicrobial agents, and necessity for timely symptom relief and infection control. Being organized and informed in one’s
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