Kidney infection, also called pyelonephritis, occurs when effective bacteria reach your kidneys as part of a urinary tract infection (UTI).
Most UTIs affect the lower part of your urethra, your urethra and bladder. Sometimes an infection that starts there goes into your upper urinary tract, affecting one or both kidneys.
If bacteria enter your body during surgery and travel from your bloodstream to the kidneys, it is also possible to get a kidney infection after the surgery. In this case, your lower urethra may not be affected.
If you have symptoms of a UTI or bladder infection – such as pain in the urine, foul-smelling urine, low back pain, or colored urine – you must seek medical attention to prevent the infection from spreading to your kidneys.
Kidney infections can be very painful and require immediate diagnosis and treatment. If your infection is not treated quickly, it can permanently damage your kidneys or spread to your bloodstream.
What Causes a Kidney Infection?
Kidney infections can be caused by bacteria or viruses that spread to your urinary tract, but bacterial infections are more common.
According to the Cleveland Clinic, in fact, about 90% of kidney infections are caused by the same type of bacteria, E. coli. (2)
Bacteria travel from your gastrointestinal tract through your urethra to your bladder, then travel through the tubes (known as the ureters) that connect your bladder and kidneys.
Usually, urine excretes any potentially harmful bacteria from your urine before it becomes an infection. But sometimes this does not happen due to the following conditions.
Structural abnormalities in your ureters or kidneys
Enlarged prostate (benign prostatic hyperplasia)
Reflux of urine from your bladder to your kidneys
Bacteria in your bloodstream can enter your kidneys and cause infections. It is usually caused by Staphylococcus, or Staphylococcus aureus.
Kidney infections that are spread through your bloodstream are born after surgery. This can happen if the prosthetic joint or heart valve is affected.
Causing a Kidney Infection It is not uncommon for kidney surgery.
How Common Are Kidney Infections?
The Cleveland Clinic estimates that between 3 and 7 out of 10,000 people in the United States have a kidney infection each year.
According to the National Institute of Diabetes and Digestive and Kidney Diseases, there are approximately 100 million hospital visits for UTIs in the United States each year, most of them related to kidney infections. (1)
Who Is at Risk for Kidney Infections?
Several factors can increase your risk of kidney infection:
As a woman in women, the opening of the urethra – where the urine comes out of the body – is close to the vagina and anus, making it easier for germs from these orbits to enter the urethra. In men, the opening of the urethra is away from the anus.
Women’s urethra is also shorter than men’s, which causes bacteria to travel to the bladder and cause infections. (3)
Being sexually active, especially for women, can make it easier for bacteria to enter your urethra for bacteria in your genital area or anus.
According to Johns Hopkins Medicine, the use of condoms with a sperm coating also increases the risk that a woman will develop a UTI. (4)
As you become pregnant, your enlarged uterus can press and squeeze against your ureters, reducing the flow of urine from your kidneys to your bladder.
This low flow of urine can make it easier for the bacteria in your bladder to move to your kidneys. (2)
Poor urine flow is a major barrier against urinary tract infections in your urinary tract. This flow can be slowed down by a narrow urethra, an enlarged prostate, or a kidney stone. (1)
Having a weakened immune system Your immune system can be weakened by health conditions such as diabetes and HIV, or by certain medications.
Wearing a catheter Long-term use of a urinary catheter to remove urine from the bladder, such as during a surgical procedure or hospital stay, increases the risk of developing a UTI.
Nerve damage If you have a spinal cord injury or nerve damage around the bladder, you may not realize that when you develop a bladder infection, it can develop in your kidneys.
Problems with urinary reflux is a medical condition called vascular reflux, which causes a small amount of urine from your bladder to pass into your kidneys and possibly carry bacteria.
The diagnosis of vesicotreal reflux is most common during childhood.
Having trouble emptying your bladder If your bladder is not completely empty, which is known as urinary retention, the rest of the urine can be helpful in causing an infection.