UTIs, like other infections, are the result of interactions between a pathogen and the host. Usually, a high bacterial virulence (ability to invade and infect) is needed to overcome normal strong host resistance. However, a compromised host is more likely to become infected even with bacteria that have low virulence. Genetically, invading bacteria with special adhesions are more likely to cause ascending UTIs that start in the urethra or bladder and move up into the ureter and kidney. Patient-specific genetic factors such as blood type and ability to produce bladder surface biofilms that protect bacteria may influence the risk for UTI (Bowen & Hellstrom, 2007).

Infectious cystitis is most commonly caused by organisms from the intestinal tract. About 90% of UTIs are caused by Escherichia coli. Less common organisms include Staphylococcus saprophyticus, Klebsiella pneumoniae, and organisms from the Proteus and Enterobacter species (Bowen & Hellstrom, 2007).

In most cases, organisms first grow in the perineal area, then move into the urethra as a result of irritation, trauma, or catheterization of the urinary tract, and finally ascend to the bladder. Catheters are the most common factor placing patients at risk for UTIs in the hospital setting. Within 48 hours of catheter insertion, bacterial colonization begins. About 50% of patients with indwelling catheters become infected within 1 week of catheter insertion.

How a catheter-related infection occurs varies between genders. Bacteria from a woman’s perineal area are more likely to ascend to the bladder by moving along the outside of the catheter. In men, bacteria tend to gain access to the bladder from inside the lumen of the catheter. Any break in the closed urinary drainage system allows bacteria to move through the urinary tract. Best practices to reduce the risk for catheter contamination and catheter-related UTIs are listed in Chart 69-1.

Viral and parasitic infections are rare and usually are transferred to the urinary tract from an infection at another body site. For example, Trichomonas, a parasite found in the vagina, can also be found in the urine. Treatment of the vaginal infection (see Chapter 74) also resolves the UTI.

Noninfectious cystitis may result from chemical exposure, such as to drugs (e.g., cyclophosphamide [Cytoxan, Procytox ]), from radiation therapy, and from immunologic responses, as with systemic lupus erythematosus (SLE).

Interstitial cystitis is a rare, chronic inflammation of the bladder, urethra, and adjacent pelvic muscles that is not a result of infection. The condition affects women ten times more often than men, and the diagnosis is difficult to make. Manifestations are similar to those of infectious cystitis with voiding occurring as often as 60 times daily, more intense urgency preceding urination, and suprapubic or pelvic pain, sometimes radiating to the groin, vulva or rectum, that is relieved by voiding. Results from urinalysis and urine culture are negative for infection (Evans & Sant, 2007; Siegel et al., 2008).

Although cystitis is not life threatening, infectious cystitis can lead to life-threatening complications, including pyelonephritis and sepsis. Severe kidney damage is a rare complication unless the patient also has other predisposing factors, such as anatomic abnormalities, pregnancy, obstruction, reflux, calculi, or diabetes.

The spread of the infection from the urinary tract to the bloodstream is termed urosepsis and is more common among older adults (Kessenich, 2010). Sepsis from any source is a systemic infection that can lead to overwhelming organ failure, shock, and death. The most common cause of sepsis in the hospitalized patient is a UTI (CDC, 2009). Sepsis has a high mortality and prolongs hospital stays (see Chapter 39).

The incidence of UTI is second only to that of upper respiratory infections in primary care. Patients who have frequency (an urge to urinate frequently in small amounts), dysuria (pain or burning with urination), and urgency (the feeling that urination will occur immediately) account for more than 5 million health care visits annually. About 50% of these patients will have a confirmed UTI (U.S. Renal Data Systems, 2010).

Frequency, urgency, and dysuria are the common manifestations of a urinary tract infection (UTI), but other manifestations may be present (Chart 69-3). Urine may be cloudy, foul smelling, or blood tinged. Ask the patient about risk factors for UTI during the assessment (see Table 69-1). For noninfectious cystitis, the Pelvic Pain and Urgency/Frequency (PUF) Patient Symptom Scale can identify patients with interstitial cystitis.

Laboratory assessment for a UTI is a urinalysis with testing for leukocyte esterase and nitrate. The combination of a positive leukocyte esterase and nitrate is 68% to 88% sensitive in the diagnosis of a UTI (Bowen & Hellstrom, 2007). Although a urinalysis can include a microscopic count of bacteria, white blood cells (WBCs), and red blood cells (RBCs), this additional testing is more expensive, is time consuming, and may not improve diagnostic accuracy. The presence of more than 20 epithelial cells/high power field (hpf) suggests contamination. The presence of 100,000 colonies/mL or the presence of three or more WBCs (pyuria) with RBCs (hematuria) indicates infection.

A urinalysis is performed on a clean-catch midstream specimen. If the patient cannot produce a clean-catch specimen, you may need to obtain the specimen with a small-diameter (6 Fr) catheter. For a routine urinalysis, 10 mL of urine is needed; smaller quantities are sufficient for culture.

A urine culture confirms the type of organism and the number of colonies. Urine culture is expensive, and results take at least 48 hours. It is indicated when the UTI is complicated or does not respond to usual therapy or the diagnosis is uncertain. A UTI is confirmed when more than 10⁵ colony-forming units are in the urine from any patient. In patients who also have symptoms of UTI, as few as 10³ colony-forming units may allow the diagnosis to be made. The presence of many different types of organisms in low colony counts usually indicates that the specimen is contaminated. Sensitivity testing follows culture results when complicating factors are present (e.g., stones or recurrent infection), when the patient is older, or to ensure the appropriate antibiotics are prescribed.

Occasionally the serum WBC count may be elevated, with the differential WBC count showing a “left shift” (see Chapter 19). This shift indicates that the number of immature WBCs is increasing in response to the infection. As a result, the number of bands, or immature WBCs, is elevated. Left shift most often occurs with urosepsis and rarely occurs with uncomplicated cystitis, which is a local rather than a systemic infection.

The diagnosis of cystitis is based on the history, physical examination, and laboratory data. If urinary retention and obstruction of urine outflow are suspected, urography, abdominal sonography, or computed tomography (CT) may be needed to locate the site of obstruction or the presence of calculi. Voiding cystourethrography (see Chapter 68) is needed when ureteral reflux is suspected.

Cystoscopy (see Chapter 68) may be performed when the patient has recurrent UTIs (more than three or four a year). A urine culture is performed first to ensure that no infection is present. If infection is present, the urine is sterilized with antibiotic therapy before the procedure to reduce the risk for sepsis. Cystoscopy identifies abnormalities that increase the risk for cystitis. Such abnormalities include bladder calculi, bladder diverticula, urethral strictures, foreign bodies (e.g., sutures from previous surgery), and trabeculation (an abnormal thickening of the bladder wall caused by urinary retention and obstruction). Retrograde pyelography, along with the cystoscopic examination, shows outlines and images of the drainage tract. Areas of obstruction or malformation and the presence of reflux are then identified early.

Cystoscopy is needed to accurately diagnose interstitial cystitis. A urinalysis usually shows WBCs and RBCs but no bacteria. Common findings in interstitial cystitis are a small-capacity bladder, the presence of Hunner’s ulcers (a type of bladder lesion), and small hemorrhages after bladder distention.

Surgery for cystitis treats the conditions that increase the risk for recurrent UTIs (e.g., removal of obstructions and repair of vesicoureteral reflux). Procedures may include cystoscopy (see Chapter 68) to identify and remove calculi or obstructions.