eMedicine Specialties > Emergency Medicine > Genitourinary

Urinary Tract Infection, Female

Author: David S Howes, MD, Residency Program Director, Professor of Medicine, Section of Emergency Medicine, University of Chicago/Pritzker School of Medicine
Contributor Information and Disclosures

Updated: Jan 31, 2008

Introduction

Background

Urinary tract infection (UTI) is defined as significant bacteriuria in the presence of symptoms. This common clinical entity accounts for a significant number of emergency department (ED) visits. It affects an estimated 20% of women at some time during their lifetimes.

Successful emergent management includes proper specimen collection, use of immediately available laboratory testing for presumptive diagnosis, appreciation of epidemiological and host factors that may identify patients with clinically inapparent upper UTI, and selection of appropriate antimicrobial therapy with recommendations for follow-up care.

Pathophysiology

The urinary tract is normally sterile. Uncomplicated UTI involves the urinary bladder in a host without underlying renal or neurologic disease. The clinical entity is termed cystitis and represents bladder mucosal invasion, most often by enteric coliform bacteria (eg, Escherichia coli) that inhabit the periurethral vaginal introitus and ascend into the bladder via the urethra.

Sexual intercourse may promote this migration, and cystitis is common in otherwise healthy young women. Urine is generally a good culture medium; factors unfavorable to bacterial growth include a low pH (5.5 or less), a high concentration of urea, and the presence of organic acids derived from a diet that includes fruits and protein. Organic acids enhance acidification of the urine.

Frequent and complete voiding has been associated with a reduction in the incidence of UTI. Normally, a thin film of urine remains in the bladder after emptying, and any bacteria present are removed by the mucosal cell production of organic acids. If the mechanisms of the lower urinary tract fail, upper tract or kidney involvement occurs and is termed pyelonephritis. Host defenses at this level include local leukocyte phagocytosis and renal production of antibodies that kill bacteria in the presence of complement.

Complicated UTI occurs in the setting of underlying structural, medical, or neurologic disease. Patients with a neurogenic bladder or bladder diverticulum and postmenopausal women with bladder or uterine prolapse have an increased frequency of UTI due to incomplete bladder emptying. This eventually allows residual bacteria to overwhelm local bladder mucosal defenses. The high urine glucose content and the defective host immune factors in patients with diabetes mellitus also predispose to infection.

Frequency

United States

UTI accounts for over 6 million patient visits to physicians per year in the United States. Approximately one fifth of those visits are to EDs.

International

As 1 in 5 adult women experience UTI at some point, it is an exceedingly common, clinically apparent, worldwide patient problem.

Mortality/Morbidity

• Although simple lower UTI (cystitis) may resolve spontaneously, effective treatment lessens the duration of symptoms and reduces the incidence of progression to upper UTI.
• Pyelonephritis is associated with substantial morbidity, including systemic effects such as fever, vomiting, dehydration, and loss of vasomotor tone resulting in hypotension. Complications include acute papillary necrosis with possible development of ureteral obstruction, septic shock, and perinephric abscess. Chronic pyelonephritis may lead to scarring with diminished renal function.
• Younger patients have the lowest rates of morbidity and mortality. Unfortunately, despite appropriate intervention, 1-3% of patients with acute pyelonephritis die. Factors associated with unfavorable prognosis are general debility and old age, renal calculi or obstruction, recent hospitalization or instrumentation, diabetes mellitus, sickle cell anemia, underlying carcinoma, intercurrent chemotherapy, or chronic nephropathy.

Race

No racial predilection exists.

Sex

The natural history of UTI varies with sex and age.

• Of neonates, boys are slightly more likely than girls to present with UTI as part of a gram-negative sepsis syndrome. The incidence in preschool children is approximately 2% and is 10 times more common in girls. Five percent of school-aged girls experience UTI. It is rare in school-aged boys.
• The largest group of patients with UTI is adult women. The incidence increases with age and sexual activity. Rates of infection are high in postmenopausal women because of bladder or uterine prolapse causing incomplete bladder emptying; loss of estrogen with attendant changes in vaginal flora; loss of lactobacilli, which allows periurethral colonization with gram-negative aerobes, such as E coli; and higher likelihood of concomitant medical illness, such as diabetes.
• UTI is unusual in males younger than 50 years, and symptoms of dysuria and frequency are usually due to urethral or prostatic infection. In older men, however, the incidence of UTI rises because of prostatic obstruction or subsequent instrumentation.

Clinical

History

• The classical symptoms of UTI in the adult are primarily dysuria with accompanying urinary urgency and frequency.
• A sensation of bladder fullness or lower abdominal discomfort is often present.
• Bloody urine is reported in as many as 10% of cases of UTI in otherwise healthy women; this condition is called hemorrhagic cystitis.
• Fevers, chills, and malaise may be noted, though these are associated more frequently with upper UTI (ie, pyelonephritis).
• Because of the referred pain pathways, even simple lower UTI may be accompanied by flank pain and costovertebral angle tenderness. In the ED, assume that the presence of these symptoms represents upper UTI.
• A history of vaginal discharge suggests that vaginitis, cervicitis, or pelvic inflammatory disease is responsible for symptoms of dysuria; therefore, a pelvic examination must be performed.
• Important additional information includes a history of prior sexually transmitted disease (STD) and multiple current sexual partners.

Physical

• Most adult women with simple lower UTI have suprapubic tenderness with no evidence of vaginitis, cervicitis, or pelvic tenderness (eg, cervical motion tenderness, which suggests pelvic inflammatory disease).
• The patient appears uncomfortable but not toxic.
• The patient with pyelonephritis usually appears ill and, in addition to fever, sweating, and prostration, is found to have costovertebral angle (flank) tenderness in the majority of cases.
• The clinician may appreciate signs of dehydration, such as dry mucous membranes and tachycardia, as well as poor vascular tone due to gram-negative bacteremia, which may be manifested by clammy extremities and profound orthostatic hypotension.

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