What is it?
Kidney infection (pyelonephritis) is a specific type of urinary tract infection (UTI) that generally begins in your urethra or bladder and travels up into your kidneys.
A kidney infection requires prompt medical attention. If not treated properly, a kidney infection can permanently damage your kidneys or spread to your bloodstream and cause a life-threatening infection.
Kidney infection treatment usually includes antibiotics and often requires hospitalization.
Signs and symptoms of a kidney infection may include:
- Back, side (flank) or groin pain
- Abdominal pain
- Frequent urination
- Strong, persistent urge to urinate
- Burning sensation or pain when urinating
- Pus or blood in your urine (hematuria)
Kidney infection typically occurs when bacteria enter your urinary tract through the urethra and begin to multiply. Bacteria from an infection elsewhere in your body also can spread through your bloodstream to your kidneys. Kidney infection is unusual through this route, but it can occur in some circumstances — for instance, when a foreign body, such as an artificial joint or heart valve, gets infected. Rarely, kidney infection results after kidney surgery.
Factors that increase your risk of a kidney infection include:
- Female anatomy. Women have a greater risk of kidney infection than do men. A woman's urethra is much shorter than a man's, so bacteria have less distance to travel from outside the body to the bladder. The proximity of the urethra to the vagina and anus also creates more opportunities for bacteria to enter the bladder. Once in the bladder, an infection can spread to the kidneys.
- Obstruction in the urinary tract. Anything that impedes the flow of urine or reduces your ability to completely empty your bladder when urinating, such as a kidney stone, structural abnormalities in your urinary system or, in men, an enlarged prostate gland, can increase your risk of kidney infection.
- Weakened immune system. Medical conditions that impair your immune system, such as cancer, diabetes or the human immunodeficiency virus (HIV), increase your risk of kidney infection. Certain medications, such as drugs taken to prevent rejection of transplanted organs, have a similar effect.
- Damage to nerves around the bladder. Nerve or spinal cord damage may block the sensations of a bladder infection so that you're unaware when it's advancing to a kidney infection.
- Prolonged use of a urinary catheter. Urinary catheters are tubes used to drain urine from the bladder. You may have a catheter placed in your bladder during and after some surgical procedures and diagnostic tests. A catheter may be used continuously if you're confined to a bed.
- A condition that causes urine to flow the wrong way. In vesicoureteral reflux, small amounts of urine flow from your bladder back up into your ureters and kidneys. People with vesicoureteral reflux may have frequent kidney infections during childhood and are at higher risk of kidney infection during both childhood and adulthood.
If left untreated, a kidney infection can lead to potentially serious complications, such as:
- Permanent kidney damage. A kidney infection can lead to permanent kidney damage that causes chronic kidney failure.
- Blood poisoning (septicemia). Your kidneys filter waste from your blood and then return your blood to the rest of your body. If you have a kidney infection, the bacteria can spread as the kidneys return blood to circulation.
- Pregnancy complications. Women who develop a kidney infection during pregnancy may have an increased risk of delivering low birth weight babies.
Your doctor may suspect you have a kidney infection based on your signs and symptoms, such as fever and upper back pain. If your doctor suspects you have kidney infection, he or she will likely ask for a urine sample to determine whether bacteria, blood or pus is in your urine.