Urinary Tract Infection Basics

Most uncomplicated urinary tract infections are ascending infections. Uropathogens—predominantly Escherichia coli, with Klebsiella pneumoniae, Proteus mirabilis, Staphylococcus saprophyticus, and Enterococcus faecalis occurring less often—colonize the periurethral area, enter the urethra, and reach the bladder. Infection confined to the bladder is cystitis. When organisms travel through the ureters into the renal pelvis and kidney tissue, the result is pyelonephritis. That anatomic distinction changes urgency and treatment. A patient with dysuria and frequency may have lower-tract disease, while fever, rigors, flank pain, costovertebral angle tenderness, vomiting, or systemic instability suggests that infection has moved beyond the bladder. A positive urine culture does not automatically mean UTI. Asymptomatic bacteriuria is significant bacterial growth in a person without urinary tract symptoms. In most populations, it is colonization that should not be screened for or treated. Antibiotics in that situation expose the patient to adverse effects and resistance without improving outcomes. The important exceptions are pregnancy and an upcoming endoscopic urologic procedure expected to cause mucosal trauma. Screening and treating asymptomatic bacteriuria during pregnancy lowers the risk of pyelonephritis. Screening is not recommended for nonpregnant...