Editing Pyelonephritis (section)

==Causes==
Most cases of community-acquired pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are ''[[Escherichia coli|E.&nbsp;coli]]'' (70-80%) and ''[[Enterococcus faecalis]]''. [[Nosocomial infection|Hospital-acquired infections]] may be due to [[coliform bacteria]] and enterococci, as well as other organisms uncommon in the community (e.g., ''[[Pseudomonas aeruginosa]]'' and various species of ''[[Klebsiella]]''). Most cases of pyelonephritis start off as lower urinary tract infections, mainly [[cystitis]] and [[prostatitis]].<ref name=Ramakrishnan2005/> ''E. coli'' can invade the [[facet cell|superficial umbrella cell]]s of the bladder to form intracellular bacterial communities (IBCs), which can mature into [[biofilm]]s. These biofilm-producing ''E. coli'' are resistant to antibiotic therapy and immune system responses, and present a possible explanation for recurrent urinary tract infections, including pyelonephritis.<ref name=Hultgren2011>{{cite web|last=Hultgren|first=SJ|title=Pathogenic Cascade of E. coli UTI|work=UTI Pathogenesis|publisher=Molecular Microbiology and Microbial Pathogenesis Program, Washington University|location=St. Louis, Missouri|year=2011|url=http://www.hultgrenlab.wustl.edu/pathcascade.shtml|access-date=5 June 2011|url-status=dead|archive-url=https://web.archive.org/web/20060829090655/http://www.hultgrenlab.wustl.edu/pathcascade.shtml|archive-date=29 August 2006}}</ref> Risk is increased in the following situations:<ref name=Ramakrishnan2005/><ref name=Scholes2005>{{cite journal | vauthors = Scholes D, Hooton TM, Roberts PL, Gupta K, Stapleton AE, Stamm WE | title = Risk factors associated with acute pyelonephritis in healthy women | journal = Annals of Internal Medicine | volume = 142 | issue = 1 | pages = 20–27 | date = January 2005 | pmid = 15630106 | pmc = 3722605 | doi = 10.7326/0003-4819-142-1-200501040-00008 }}</ref>
* Mechanical: any structural abnormalities in the urinary tract, [[vesicoureteral reflux]] (urine from the bladder flowing back into the [[ureter]]), [[kidney stone]]s, [[Urinary catheterization|urinary tract catheterization]], [[Ureteric stent|ureteral stents]] or drainage procedures (e.g., [[nephrostomy]]), [[pregnancy]], [[neurogenic bladder]] (e.g., due to spinal cord damage, [[spina bifida]] or [[multiple sclerosis]]) and [[prostate]] disease (e.g., [[benign prostatic hyperplasia]]) in men
* Constitutional: [[diabetes mellitus]], [[Immunodeficiency|immunocompromised]] states
* Behavioral: change in sexual partner within the last year, [[spermicide]] use
* Positive [[family history]] (close family members with frequent urinary tract infections)