Pyelonephritis - Causes

Causes

Most cases of "community-acquired" pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are E. coli (70–80%) and Enterococcus faecalis. 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. E. coli can invade the superficial umbrella cells of the bladder to form intracellular bacterial communities (IBCs), which can mature into biofilms. 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. Risk is increased in the following situations:

• Mechanical: any structural abnormalities in the urinary tract, vesicoureteral reflux (urine from the bladder flowing back into the ureter), kidney stones, urinary tract catheterization, 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, immunocompromised states
• Behavioral: change in sexual partner within the last year, spermicide use
• Positive family history (close family members with frequent urinary tract infections)