Urinary Tract Infections

September 29, 2011

Urinary tract infections (UTIs) are one of the most common medical problems that cause women to seek medical attention. In most cases Urinary Tract Infections are a nuisance; a medical problem that produces uncomfortable symptoms that appropriate outpatient treatment can quickly alleviate. While usually a benign condition, Urinary Tract Infections do have the potential to become a serious medical problem, requiring hospitalization and aggressive therapy.

Urinary Tract Infections are defined as the presence of bacteria anywhere in the urinary tract. Most commonly, Urinary Tract Infections result from bacteria growing in the bladder, and producing cystitis, a term that is often used interchangeably with Urinary Tract Infections. Cystitis refers to infection limited to the bladder, while the term UTI includes other structures such as the kidneys, ureters, and urethra. Urinary Tract Infections can be defined as complicated and uncomplicated. Complicated Urinary Tract Infections refer to cases in which there are functional or anatomic abnormalities of the urinary tract, underlying host abnormalities, or infection of the kidneys or ureters. Uncomplicated Urinary Tract Infections refer to cases without these factors and account for 80% of cases. Complicated Urinary Tract Infections require more aggressive or prolonged treatment and are associated with increased morbidity. In greater than 99% of cases, bacteria gain access to the urinary tract by ascending via the urethra; in rare cases, infection can result from the spread of bacteria to the kidney via the bloodstream or other routes.

Urinary Tract Infections are very common among sexually active young women, with approximately one third of women having a UTI within 10 years of the onset of sexual activity. Most Urinary Tract Infections in sexually active young women are uncomplicated cystitis. There are about 25 million cases of acute cystitis per year in the United States, with most of these cases treated by physicians. Sexual activity predisposes women to Urinary Tract Infections by inoculation of urinary tract pathogens into the urethra and by acquisition of strains of Escherichia coli (see below) that are urinary tract pathogens. Many women are prone to frequent Urinary Tract Infections and contract them commonly after sexual activity. Some women are more susceptible to Urinary Tract Infections due to cell surface markers in the bladder that favor bacterial colonization, and other factors. Women with frequent uncomplicated Urinary Tract Infections sometimes employ a self-treatment strategy without physician intervention for each episode.

Elderly women are more susceptible to bacterial colonization of the bladder. The reasons for this are not fully known but are thought to be related to anatomic changes that lead to incomplete voiding and estrogen deficiency. Elderly women may have significant numbers of bacteria in their bladder without having any symptoms; this is termed “asymptomatic bacteuria.” Prospective studies have shown that asymptomatic bac-teuria in elderly women resolves spontaneously and does not require antibiotic therapy. There is no reason to screen for bacteuria and treat asymptomatic elderly women. When symptomatic Urinary Tract Infections do occur in the elderly, they are more often complicated due to factors such as the presence of bladder catheters, anatomic or functional abnormalities, and other comorbidities.

Urinary Tract Infections in pregnancy can cause preterm labor and low birthweight. Physiologic and anatomic changes related to pregnancy make pregnant women more susceptible to Urinary Tract Infections and more likely to have complications. In contrast to elderly women, asymptomatic bacteuria in pregnant women has been shown to lead to complicated Urinary Tract Infections, and should be treated. Screening and treating asymptomatic bacteuria in the first trimester has been shown to decrease the incidence of complicated Urinary Tract Infections later in pregnancy.

Women with uncomplicated Urinary Tract Infections present with pain and burning on urination, difficulty voiding, and frequent urination. There may be visible blood in the urine, which can be quite dramatic. The onset of these symptoms can be very acute. There may be some overlap in symptoms between Urinary Tract Infections and urethritis due to sexually transmitted diseases (STDs) such as herpes, gonorrhea, and chlamydia, which can also produce burning on urination. A urinalysis demonstrating the presence of white blood cells and bacteria in the urine will differentiate between burning on urination from UTI versus urethritis from STDs. Frail elderly women with Urinary Tract Infections may present with more subtle findings such as lethargy and decreased oral intake without specific symptoms related to the urinary tract.

Urinary Tract Infections involving the kidney (termed pyelonephritis) produce additional symptoms compared to simple cystitis. In addition to burning and frequency, patients with pyelonephritis present with flank pain and tenderness, fever chills, nausea, and vomiting. Other conditions that produce symptoms that overlap with those of pyelonephritis include pelvic inflammatory disease, acute appendicitis, kidney stones, and diverticulitis. Acute pyelonephritis can be complicated by sepsis, and patients are often admitted for inpatient therapy.

The bacterium that most often causes Urinary Tract Infections is E. coli, which is a normal inhabitant of the gastrointestinal (GI) tract and perineum. There are specific strains of E. coli that are pathogenic (disease-causing) for the urinary tract due to their ability to adhere to the lining of the bladder and other factors. Colonization with one of these “uropathogenic” strains of E. coli may lead to recurrent bouts of Urinary Tract Infections, which then stop once this strain is eliminated. In addition to E. coli, a variety of other bacteria that are normal inhabitants of the GI tract cause Urinary Tract Infections, including Klebsiella, Enterococcus, and Proteus Staphylococcus saprophyticus is a common pathogen (disease-causing agent) in sexually active young women. Patients residing in long-term care facilities, hospitalized patients, and patients with chronic bladder catheters may become infected with pathogens that are difficult to treat including bacteria that have acquired resistance to commonly used antibiotics.

Treatment of acute uncomplicated cystitis consists of a short course of antibiotics (3 days) and adequate hydration (fluid intake). Complicated Urinary Tract Infections require a longer course of antibiotics, usually 7-10 days. Patients with pyelonephritis are often admitted and treated with intravenous antibiotics. The specific antibiotics used will depend on issues of cost, changing susceptibility patterns of UTI pathogens, and the patient’s history of allergies and prior treatment. Cranberry juice has not been shown to be effective in treating an established UTI, but may be beneficial in preventing Urinary Tract Infections by impeding bacteria from adhering to the bladder wall. Adequate fluid intake can also help prevent Urinary Tract Infections as bacteria are flushed out of the bladder by urination before an infection is established. For women who have Urinary Tract Infections frequently after sexual activity, drinking one or two glasses of water resulting in increased urine production has been shown to prevent Urinary Tract Infections.

See Also: Gonorrhea, Herpes simplex virus, Sexually transmitted diseases

Suggested Reading

  • Ronald, R. A. (2002). Urinary tract infections in adults. In J. S. Tan (Ed.), Experts guide to the management of common infectious diseases (pp. 229-250). Philadelphia: American College of Physicians.


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