Risk Factors and Causes of Kidney Infection

Kidney infections usually begin as lower urinary tract infections, which can involve a backflow of infected urine. Bacteria multiply in the bladder and then travel to the kidneys. In some cases, bacteria enter the kidneys through the bloodstream or through the use of medical equipment (e.g., catheter, cystoscope).

Women are more likely to develop kidney infections than men because of their physical makeup. In women, the urethra is shorter, which allows bacteria to spread to the bladder, and eventually, the kidneys, more quickly.

Also, the urethral opening is closer to the anus (opening of the rectum) in women, allowing bacteria to spread from the anus to the urethra easier. Sexually active women are at additional risk for kidney infections, particularly if they use contraceptive methods that can carry bacteria (e.g., diaphragm, spermicides).

The elderly and patients who have diabetes, cancer, or HIV/AIDS are at increased risk for developing kidney infections.

Other kidney infection risk factors include the following:

  • Conditions such as kidney stones or BPH (enlarged prostate), which make it more difficult for the body to manage urine flow
  • Congenital (present at birth) abnormalities of the urinary tract
  • Patient history of urinary tract infections (UTIs) or a certain type of bacteria
  • Spinal cord injury(may prevent patients from experiencing pain and other symptoms of kidney infection)
  • Vesicoureteral reflux (VUR; causes urine to back up from the bladder into the kidneys)

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 03 Jun 2007

Last Modified: 22 Sep 2015