Urinary tract infections are among the most common entities encountered in medical practice. In acute infections, a single pathogen is usually found, whereas two or more pathogens are often seen in chronic infections. Coliform bacteria are responsible for most non-nosocomial, uncomplicated urinary tract infections, with Escherichia coli being the most common. Such infections typically are sensitive to a wide variety of orally administered antibiotics and respond quickly. Nosocomial infections often are due to more resistant pathogens and may require parenteral antibiotics. Renal infections are of particular concern because if they are inadequately treated, loss of kidney function may result. A urine culture is recommended for patients with suspected urinary tract infection and ideally should be obtained prior to the initiation of antibiotic therapy. Previously, a colony count greater than 105/mL was considered the criterion for urinary tract infection, though up to 50% of women with symptomatic infections may have lower counts. In addition, the presence of pyuria correlates poorly with the diagnosis of urinary tract infection, and thus urinalysis alone is not adequate for diagnosis. With respect to treatment, tissue infections (pyelonephritis, prostatitis) require therapy for 1–2 weeks, while mucosal infections (cystitis) require only 1–3 days of therapy.
ESSENTIALS OF DIAGNOSIS
Irritative voiding symptoms.
Patient usually afebrile.
Positive urine culture; blood cultures may also be positive.
Acute cystitis is an infection of the bladder, most commonly due to the coliform bacteria (especially E coli) and occasionally gram-positive bacteria (enterococci). The route of infection is typically ascending from the urethra. Viral cystitis due to adenovirus is sometimes seen in children but is rare in immunocompetent adults. Uncomplicated cystitis in men is rare and implies a pathologic process such as infected stones, prostatitis, or chronic urinary retention requiring further investigation.
Irritative voiding symptoms (frequency, urgency, dysuria) and suprapubic discomfort are common. Women may experience gross hematuria, and symptoms may often appear following sexual intercourse. Physical examination may elicit suprapubic tenderness, but examination is often unremarkable. Systemic toxicity is absent.
Urinalysis shows pyuria, bacteriuria, and varying degrees of hematuria. The degree of pyuria and bacteriuria does not necessarily correlate with the severity of symptoms. Urine culture is positive for the offending organism, but colony counts exceeding 105/mL are not required for the diagnosis. Patients with asymptomatic bacteriuria or colonization are expected to have positive urine cultures but do not require treatment except in pregnant women. Patients with long-term urinary catheters (indwelling urinary [Foley] or suprapubic catheter) or urostomy urinary diversions are expected to be colonized with bacteria, and thus, urinalysis and urine culture are most helpful in directing therapy rather than determining whether symptomatic infection exists.