What is kidney infection (pyelonephritis)?

Infection in the urinary tract can involve the lower tract especially the bladder (cystitis), prostate (prostatitis) or the upper tract and kidney (pyelonephritis). It is usually a bacterial infection. The disease occurs in roughly three to seven of every 10,000 people in the United States. The occurrence in pregnant women is about 2 percent. It is readily treatable if diagnosed early.

A bacteria called Escherichia Coli (E Coli) causes about 90 percent of kidney infections. The bacteria migrate from the genitals through the urethra (the tube that removes urine from the body) into the bladder and up the tubes (ureters) that connect the bladder to the kidneys.

Some bacteria, such as staphylococcus infections, can enter the kidneys from the bloodstream.

What are the causes of kidney infections (pyelonephritis)?

Normally, bacteria are flushed out by the flow of urine. However, several problems can increase the risk of a kidney infection. These problems can include:

  • Structural abnormalities (strictures, stents, stones, surgery) blocking urine flow.
  • An enlarged prostate gland (benign prostatic hyperplasia) compressing the urethra.
  • Backflow (reflux) of urine from the bladder to the kidneys.
  • If your immune system is affected (low white blood cell count, use of certain medications, HIV, cancer, an organ transplant).
  • Pregnancy, during which time the enlarging uterus can squeeze the ureters and reduce the flow of urine, allowing the bacteria to migrate to the kidneys.
  • Uncontrolled diabetes mellitus.

What are the symptoms of kidney infection?

A number of symptoms can indicate to your doctor that you may have a kidney infection. The more severe the symptoms, the more likely the infection involves the kidney. Symptoms of a kidney infection include:

  • Sudden onset of chills
  • Fever over 100 degrees Fahrenheit
  • Pain in the groin, lower back or side
  • Nausea
  • Vomiting
  • Abdominal muscle spasm

More general symptoms of upper kidney infection include:

  • Flushed or reddened skin
  • Painful urination
  • Increased urination
  • Unproductive attempts to urinate despite feelings of urgency
  • General ill feelings
  • Cloudy urine
  • Abnormally colored urine
  • Blood in the urine
  • Foul smelling urine

If you experience any of these sudden onset symptoms, please seek medical attention.

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