(Infection, Kidney; Pyelonephritis)
Kidney infections may occur in one or both kidneys. An infection can cause pain and swelling which may stop the kidneys from working as needed. The kidneys remove waste and pass it out of the body as urine (pee). They also balance the water and mineral content in the blood.
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Kidney infections are caused by a bacteria. The bacteria often enters the lower part of the urinary tract first. It can then grow and cause a urinary tract infection (UTI). If the UTI is left untreated it can spread up into the kidneys. Most UTIs are caused by a bacteria that normally live in the colon or vagina. It gets passed to the opening of the urinary tract during everyday activities.
Problems with the shape of the urinary tract may also slow or block the flow of urine. This may make it easier for infections to develop.
Women have a higher risk of kidney infections than men. Other things that may raise the risk include:
- Being sexually active
- Use of spermicide
- Having a new sexual partner
- Bladder infection
Some conditions that may raise the risk of a kidney infection include:
- A weak immune system
- Bladder catheter in place or recently used
- Loss of bladder control due to a brain, spine, or nerve problem
- Renal insufficiency
- Kidney stones
- Problems in the urinary tract that slow the flow of urine, such as:
- A history of kidney transplant
Symptoms of kidney infection may include:
- Pain in the belly, lower back, side, or groin
- Urination (peeing) that may be:
- Urgent, but with only a small amount of urine
- Painful or burning
- Sensation of a full bladder—even after urination
- Fever and chills
- Nausea and vomiting
- Pus and blood in the urine
- Loss of appetite
The doctor will ask about symptoms and past health. A physical exam will be done. A sample of urine will be tested. Sometimes the urine will be tested to look for the exact type of bacteria.
A kidney infection may be suspected based on the symptoms alone. Images of the kidney may be needed for repeat infections. They can help to show problems with the structure of kidneys.
A kidney infection can be treated with antibiotics. A hospital stay may be needed with a severe kidney infection. This will allow the antibiotics to be delivered through IV.
Poorly treated or untreated kidney infections can lead to:
- A life-threatening infection that spreads throughout the body— sepsis
- Long term infection
- Scarring or lasting damage
- Severe kidney disease
Some kidney infections are caused by a problem with kidney structure. Surgery may be needed to fix the problem.
The risk of a UTI may be lowered by:
- Emptying the bladder completely after sex
- Drinking a full glass of water after having sex
- Drinking plenty of fluids throughout the day
- Correcting problems with the urinary tract
- Complicated urinary tract infection (UTI). EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/complicated-urinary-tract-infection-uti.
- Cystitis and upper urinary tract infections (UTI) in men. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/cystitis-and-upper-urinary-tract-infections-uti-in-men.
- Herness J, Buttolph A, Hammer NC. Acute Pyelonephritis in adults: rapid evidence review. Am Fam Physician. 2020;102(3):173-180.
- Kidney infection (pyelonephritis). National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: https://www.niddk.nih.gov/health-information/urologic-diseases/kidney-infection-pyelonephritis.
- Uncomplicated urinary tract infection (UTI) (pyelonephritis and cystitis). DynaMed website. Available at: https://www.dynamed.com/condition/uncomplicated-urinary-tract-infection-uti-pyelonephritis-and-cystitis.
- Mark Arredondo, MD
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