Kidney infection (Pyelonephritis) symptoms, treatment and prevention

What are the symptoms of a kidney infection?

A kidney infection can show up in different ways for everyone. Sometimes it begins with mild changes, like burning or needing to urinate more often. Other times, symptoms such as fever, vomiting, or blood in your urine signal that it's more serious and you should contact your doctor the same day or go to urgent care or the emergency room right away.

Common symptoms

• Pain or burning when you pee
• Feeling like you have to pee right after going
• Peeing more often than usual
• Pee that looks cloudy or smells bad

Moderate symptoms

• Pain in your lower back, side or groin
• Fever
• Chills

Severe or serious symptoms

• Nausea or vomiting
• Blood or pus (thick white or yellow liquid) in your urine

People who are pregnant, children and older adults may have only mild or unclear symptoms. If you are pregnant or were recently treated for a bladder infection and notice any of these signs, contact your doctor right away. If you are already on treatment for a UTI but still have symptoms, call your doctor as soon as possible.

How kidney infection symptoms differ from a bladder infection (UTI)

A bladder infection usually causes burning, needing to urinate often or cloudy, smelly urine. A kidney infection can include those signs, but often adds more serious symptoms like fever, nausea or back pain.

How will I know if I have a kidney infection?

If your doctor thinks you might have a kidney infection, they may run tests to see how serious it is. The type of test depends on your symptoms, your overall health, and how sick you feel. Some tests are quick and simple, while others help doctors look more closely at your kidneys.

To find out if you have a kidney infection, doctors may do tests such as:

• Urine tests: a simple urine sample (urinalysis) can confirm a kidney infection by checking for bacteria, white blood cells or other signs of infection in the pee. If bacteria is present, the sample will be sent for urine culture to determine the type of bacteria.
• Blood tests: these look for infection in your bloodstream (elevated white blood cell count) and help your doctor see how well your kidneys are working.
  • Estimated glomerular filtration rate (eGFR): calculated from creatinine, a waste product normally filtered by the kidneys.
  • Blood urea nitrogen (BUN): measures urea nitrogen, a waste product made when your body breaks down protein.
• Imaging tests: an ultrasound, X-ray, or CT scan may be ordered if your symptoms are serious, you're not getting better with treatment, or your doctor thinks something (like a kidney stone) might be blocking urine flow.
• Tests for certain groups
  • Rectal exam for men: checks whether an enlarged prostate is blocking urine flow.
  • Pregnant women: ultrasound is usually preferred over X-rays or CT scans to avoid radiation.
  • Children: often start with an ultrasound, with other imaging only if needed.

Your healthcare team will explain which test is best and safest for you. 

Who is more likely to get a kidney infection?

Anyone can get a kidney infection, but it is more common in some people, such as:

• Women:  A woman's urethra is shorter than a man's. Pregnant women are even more at risk for kidney infection.
• People with diabetes: A disease where your body has trouble making or using insulin, the hormone that controls blood sugar. Over time, high blood sugar can damage blood vessels and organs, including the kidneys.
• People with a weakened immune system: This could be caused by a disease, such as diabetes or HIV, or by certain medicines called immunosuppressants, which calm the immune system. People who have had a kidney transplant or other organ transplant take immunosuppressants.
• People who have nerve or spinal cord damage that prevents them from feeling pain in and around their urinary tract: This can keep them from noticing symptoms of a bladder infection, which can lead to a kidney infection.
• People who use a catheter (a thin, flexible tube) to drain urine from their bladder.
• People with vesicoureteral reflux (VUR): People with VUR have urinary tracts that allow urine to flow backwards from the bladder to the kidneys.

Special considerations 

• Pregnancy: Hormonal changes and pressure from the uterus can slow urine flow and increase risk. Kidney infections during pregnancy can become serious quickly, so any urinary symptoms should be checked right away.
• Menopause: Lower estrogen, a hormone that supports reproductive and urinary tract health, after menopause can make it easier for bacteria to grow.

Symptoms that may show up in women

Along with common signs like fever, back or side pain and burning when you pee, women may notice:

• Pelvic or lower-belly pain
• More frequent urges to pee
• Vaginal irritation 

Key points for women

• Treat bladder infections quickly; an untreated bladder infection can spread to the kidneys.
• Good habits help lower risk: drink water regularly, urinate after sex and wipe front to back after using the toilet.

What is the treatment for a kidney infection?

Immediate treatment is important

Untreated kidney infections can cause permanent kidney damage or spread to your bloodstream (sepsis), which can be life-threatening. Never wait to see if symptoms improve or go away on their own.

Antibiotic treatment

Doctors treat most kidney infections with antibiotics (medicines that kill bacteria). Doctors will often start with an antibiotic that fights the most common types of bacteria because it is very important to treat a kidney infection right away. Then, they may change the type of antibiotic after they get the results of your blood or urine tests.

Doctors will prescribe an antibiotic medicine based on:

• What type of bacteria is causing the infection
• How severe the infection is
• If you are immunocompromised (have a weak immune system)
• If you are pregnant
• If you are older than 65
• If you had problems with certain antibiotics in the past, such as allergic reactions

Most people feel better a few days after starting antibiotics.

You may hear people talk about "flushing" your kidneys with natural remedies, but once bacteria reach your kidneys, there's no safe way to wash the infection out at home. Only antibiotics (and sometimes IV medicines) can treat a kidney infection. Drinking water is healthy and can help prevent future infections, but it can't treat or cure kidney infections.

What happens if kidney infections go untreated?

Without quick and proper treatment, a kidney infection can lead to serious health problems, such as:

• Kidney damage (scarring): Ongoing infection can leave scars on the kidneys and lead to long-term loss of kidney function.
• Sepsis (blood infection): Bacteria can spread from the kidneys into the bloodstream, causing a life-threatening infection that needs emergency care.
• Repeat infections: Untreated or partly treated infections can return, sometimes becoming harder to treat.
• Pregnancy problems: In pregnant people, untreated infections can increase the risk of early labor or low birth weight.
• High blood pressure or chronic kidney disease: Repeated or severe infections can raise blood pressure and increase the risk of kidney disease.

Getting treatment as soon as you notice symptoms is the best way to protect your kidneys and overall health.

How can I prevent kidney infections?

You may be able to lower your chance of getting a kidney infection by:

• Drinking plenty of water
• Peeing as soon as you feel the need to (don't hold it)
• Urinating after having sex: Peeing right after sex helps wash bacteria out of the urethra before it can travel to the bladder or kidneys. Clearing those germs quickly lowers the risk of a urinary tract infection that could spread to the kidneys.
• For women, wiping from front to back after going to the bathroom keeps bacteria from your vagina or anus from getting into your urethra
• Avoiding the use of deodorant sprays or douches in your genital area

Can I have sex while being treated for a kidney infection?

Wait until you finish treatment and your symptoms are gone before having sex. Remember to urinate after sex to avoid getting more bacteria in your urinary tract and lower your risk of another infection.