Urinary Tract Infection, Lower
The two forms of lower urinary tract infection (UTI) are cystitis (infection of the bladder) and urethritis (infection of the urethra). They’re nearly 10 times more common in females than in males (except in elderly males) and affect 10% to 20% of all females at least once.
In males, lower UTIs typically are associated with anatomic or physiologic abnormalities and therefore need close evaluation. Most UTIs respond readily to treatment, but recurrence and resistant bacterial flare-up during therapy are possible.
Causes
Most lower UTIs result from ascending infection by a single gram-negative, enteric bacterium, such as Escherichia coli, Klebsiella, Proteus, Enterobacter, Pseudomonas, and Serratia. In a patient with neurogenic bladder, an indwelling urinary catheter, or a fistula between the intestine and bladder, a lower UTI may result from simultaneous infection with multiple pathogens.
Studies suggest that infection results from a breakdown in local defense mechanisms in the bladder that allows bacteria to invade the bladder mucosa and multiply. These bacteria can’t be readily eliminated by normal urination.
Bacterial flare-up during treatment usually is caused by the pathogen’s resistance to the prescribed antimicrobial therapy. Even a small number of bacteria (fewer than 10,000/ml) in a midstream urine specimen obtained during treatment casts doubt on the effectiveness of treatment.
In almost all patients, recurrent lower UTIs result from reinfection by the same organism or by some new pathogen. In the remaining patients, recurrence reflects persistent infection, usually from renal calculi, chronic bacterial prostatitis, or a structural anomaly that is a source of infection. The high incidence of lower UTI among females probably occurs because natural anatomic features facilitate infection. (See Risk factors for UTI.)
Complications
If untreated, chronic UTI can seriously damage the urinary tract lining. Infection of adjacent organs and structures (for example, pyelonephritis) also may occur. When this happens, the prognosis is poor unless the patient responds to systemic treatment with multiple antibiotics administered intravenously.
Assessment
The patient may complain of urinary urgency and frequency, dysuria, bladder cramps or spasms, itching, a feeling of warmth during urination, nocturia, and urethral discharge (in males). Other complaints include lower back pain, malaise, nausea, vomiting, pain or tenderness over the bladder, chills, and flank pain. Inflammation of the bladder wall also causes hematuria and fever.
Diagnostic tests
The following tests are used to diagnose lower UTI:
Microscopic urinalysis showing red blood cell and white blood cell counts greater than 10 per high-power field suggests lower UTI.
Clean-catch urinalysis revealing a bacterial count of more than 100,000/ml confirms UTI. Lower counts don’t necessarily rule out infection, especially if the patient is urinating frequently, because bacteria require 30 to 45 minutes to reproduce in urine. Clean-catch collection is preferred to catheterization, which can reinfect the bladder with urethral bacteria.
Sensitivity testing
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