Acute pyelonephritis.

Microbial factors that contribute to the virulence of uropathogens, and host factors that predispose to urinary tract infection are summarized in this article. The limitations of methods used to differentiate between upper and lower urinary tract infections are discussed. Recommendations for the treatment of pyelonephritis and its complications are outlined, with an emphasis on the use of safe, potent, renally excreted antimicrobials.