What Causes It?

Bacteria usually cause pyelonephritis. The most common type of bacteria that causes pyelonephritis is Escherichia coli (E. coli), which can live in the digestive tract, in the vagina, or around the urethra. In most cases, these bacteria enter the urethra and travel to the bladder and kidneys. However, your body will usually remove the bacteria and you will not have symptoms.

Risk Factors for Pyelonephritis

Doctors can seldom explain why one person will get pyelonephritis and another person will not. However, pyelonephritis research has shown that people with certain risk factors are more likely than others to develop pyelonephritis. A risk factor is anything that increases a person's chance of developing a disease.
Pyelonephritis risk factors include:
  • Infections in the bladder (see UTI Risk Factors)
  • Use of a catheter to drain urine from the bladder
  • Use of a cystoscope to examine the bladder or urethra
  • Surgery on the urinary tract
  • Conditions such as prostate enlargement and kidney stones
  • Gender and age (females and the elderly are much more likely to get pyelonephritis).


Pyelonephritis symptoms can include:
  • Pain or stinging when you pass urine
  • Frequent or intense urges to urinate, even when you have little urine to pass
  • Back, side, or groin pain
  • Urine that smells bad or looks milky, cloudy, or reddish in color
  • Nausea and vomiting
  • Fever or chills.
Not everyone with pyelonephritis will have symptoms, especially in the elderly or debilitated. However, they may experience symptoms such as: an altered mental state, fever, or low blood pressure. Children are more likely to have a fever and no other symptoms of pyelonephritis, which may lead to a misdiagnosis.
Last reviewed by: Arthur Schoenstadt, MD
9 Signs You May Have Inattentive Type Adult ADHD