What Are Kidney Infections?

The main jobs of your kidneys are to clean the waste and remove extra water from your blood. They’re part of your urinary tract, which makes pee (urine) and removes it from your body. Like the exhaust system on your car, you want everything in good working order so waste moves in one direction only: out.

The urinary tract is made up of your:

  • Kidneys (to clean waste from your blood and make pee)
  • Ureters (thin tubes, one for each kidney, that carry pee to your bladder)
  • Bladder : (stores pee)
  • Urethra: (carries pee from the bladder to outside your body)

If any of these parts get bacteria in them, you can get a urinary tract infection (UTI). Most often, it’s the bladder that gets infected. It can be painful, but not usually too serious. But if those bacteria travel up the ureters, you can have a much more serious problem: a kidney infection. Doctors sometimes call this “pyelonephritis.”

You need to have a kidney infection treated right away. If you don’t, it can lead to life-threatening problems.

What Causes a Kidney Infection?

Usually, it starts with a bladder infection that spreads to the kidney. Usually, bacteria called E. coli cause the infection to begin with. Other bacteria can also cause kidney infections.

It’s rare, but you can also have an infection that gets in through your skin, makes its way into your blood, then travels to your kidney. You can get an infection after kidney surgery, too, but that’s very uncommon.

Who Gets Them?

Anyone can. But just as women get more bladder infections than men, they also get more kidney infections.

A woman’s urethra is shorter than a man’s, and it’s closer to the vagina and anus, where bacteria live. That means it’s easier for bacteria to get into a woman’s urethra, and once they do, it’s a shorter trip to the bladder. From there, they can spread to the kidneys.

Pregnant women are even more likely to get bladder infections because the baby can put pressure on the woman’s ureters and slow the flow of urine.


Any problem in your urinary tract that prevents pee from flowing forward can raise your chances of a kidney infection, such as:

  • Blockage in the urinary tract, like a kidney stone or enlarged prostate
  • Conditions that keep the bladder from completely emptying
  • Structural problem in the urinary tract, like a pinched urethra
  • Vesicoureteral reflux (VUR), a condition where pee flows backward from the bladder toward the kidneys

You are also more likely to get one if you have:


You may have:

You may also have some of the same signs and symptoms as with a bladder infection, such as:

  • Burning or pain when you pee
  • Constant urge to pee, even though you just went
  • Cloudy or bad-smelling urine
  • Pain in your lower belly
  • Peeing much more often than normal

Call your doctor if you have these symptoms and think it may be a kidney infection, especially if you have a UTI and you’re not getting any better. If you don’t get treated, it could lead to kidney damage or blood infection, which is life-threatening. Also, if you’re pregnant, a kidney infection can affect your baby.

How Is It Diagnosed?

After asking about your signs and symptoms, your doctor will likely start with a:

  • Urine analysis to check for blood, pus, and bacteria in your pee
  • Urine culture to see what kind of bacteria you have

Your doctor may also use these tests:

  • Ultrasound or CT: to check for a blockage in your urinary tract. These are usually done if treatment doesn’t help within the first 3 days.
  • Voiding cystourethrogram (VCUG): a type of X-ray to look for problems in your urethra and bladder. These are often used in children who have VUR.
  • Digital rectal exam (for men): (Your doctor inserts a lubed finger into your anus to check for a swollen prostate.)
  • Dimercaptosuccinic acid (DMSA) scintigraphy: a type of imaging that uses a radioactive material to better see kidney infection and damage



Usually, the first step is antibiotics, which you may need for a week or two. Your symptoms should improve within a few days, but make sure to finish the medicine as your doctor tells you to.

For severe infections, you’ll need to stay in the hospital and get antibiotics through an IV.

If you get kidney infections that keep coming back, you may have a structural problem in your urinary tract. For that, your doctor may refer you to a specialist, such as a urologist, who treats urinary tract problems. These types of issues often need surgery.

How to Feel Better

To help ease your symptoms, you can:

  • Drink plenty of fluids to flush out the bacteria.
  • Get extra rest.
  • Sit on the toilet, don’t squat over it, which can prevent your bladder from completely emptying
  • Take a pain reliever with acetaminophen but avoid aspirin, ibuprofen, and naproxen.
  • Use a heating pad on your belly, back, or side


You can’t completely prevent all bladder infections. But you may be less likely to get one if you:

  • Avoid deodorant sprays or douches on your genitals
  • Don’t use condoms or diaphragms with spermicide. It can trigger bacteria growth. But do use lubricated condoms, since without lube it can irritate the urethra, which makes infection more likely.
  • Drink lots of water.
  • Go to the bathroom as soon as you feel the urge.
  • Pee after having sex.
  • Wipe front to back after going to the bathroom.
WebMD Medical Reference Reviewed by Minesh Khatri, MD on February 10, 2019



American Kidney Fund: “About Your Kidneys,” “Kidney Infection.”

KidsHealth: “Urinary Tract Infections.”

Victoria State Government: “Cystitis.”

NHS: “Cystitis,” “Kidney Infection.”

Mayo Clinic: “Kidney Infections.”

NIH, National Institute of Diabetes and Digestive and Kidney Diseases: “Kidney Infection (Pyelonephritis).”

Merck Manual: “Kidney Infection (Pyelonephritis).”

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