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)
- Urine that smells bad or is cloudy
When to see a doctor
Make an appointment with your doctor if you have any signs or symptoms that worry you. Also make an appointment if you're being treated for a urinary tract infection but your signs and symptoms aren't improving.
Severe kidney infection can lead to life-threatening complications. Seek immediate medical attention if you experience typical kidney infection symptoms combined with bloody urine or nausea and vomiting.
Kidney infection typically occurs when bacteria enter your urinary tract through the tube that carries urine from your body (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 happen — for instance, if you have an artificial joint or heart valve that becomes 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. Pregnant women are at higher risk of a kidney infection.
- Obstruction in the urinary tract. Anything that slows 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 diabetes and 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 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 childhood and adulthood.
If left untreated, a kidney infection can lead to potentially serious complications, such as:
- Permanent kidney damage. Permanent kidney damage can lead to chronic kidney disease.
- 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.
Reduce your risk of kidney infection by taking steps to prevent urinary tract infections. Women, in particular, may reduce their risk of urinary tract infections if they:
- Drink plenty of fluids, especially water. Drinking fluids can help remove bacteria from your body when you urinate.
- Urinate frequently. Avoid delaying urination when you feel the urge to urinate.
- Empty the bladder after intercourse. Urinating as soon as possible after intercourse helps clear bacteria from the urethra, reducing your risk of infection.
- Wipe carefully. Wiping from front to back after urinating and after a bowel movement helps prevent bacteria from spreading to the urethra.
- Avoid using feminine products in the genital area. Using feminine products, such as deodorant sprays or douches, in your genital area can irritate your urethra.