Mayo Article - Monument Health

Overview

A kidney infection is a type of urinary tract infection (UTI). A kidney infection may begin in the tube that carries urine from the body (urethra) or in the bladder. The infection can travel to one or both kidneys. A kidney infection is also called pyelonephritis.

A kidney infection needs prompt medical treatment. If not treated properly, an infection can cause lasting damage to the kidneys. Or the bacteria can spread to the bloodstream and cause a dangerous infection.

Kidney infection treatment often includes antibiotics, which might be given in the hospital.

Female urinary system — Your urinary system includes the kidneys, ureters, bladder and urethra. The urinary system removes waste from the body through urine. The kidneys are located toward the back of the upper abdomen. They filter waste and fluid from the blood and produce urine. Urine moves from the kidneys through narrow tubes to the bladder. These tubes are called the ureters. The bladder stores urine until it's time to urinate. Urine leaves the body through another small tube called the urethra.

Male urinary system — Your urinary system includes the kidneys, ureters, bladder and urethra. The urinary system removes waste from the body through urine. The kidneys are located toward the back of the upper abdomen. They filter waste and fluid from the blood and produce urine. Urine moves from the kidneys through narrow tubes to the bladder. These tubes are called the ureters. The bladder stores urine until it's time to urinate. Urine leaves the body through another small tube called the urethra.

Symptoms

Symptoms of a kidney infection might include:

Fever
Chills
A burning feeling or pain when urinating
Having to urinate often
A strong, lasting urge to urinate
Back, side or groin pain
Nausea and vomiting
Pus or blood in the urine
Urine that smells bad or is cloudy
Belly pain

When to see a doctor

Make an appointment with your health care provider if you have symptoms of a kidney infection. Also see your provider if you're being treated for a UTI but your symptoms aren't getting better.

A severe kidney infection can lead to dangerous complications. They may include blood poisoning, damage to the body's tissues or death. Seek medical care right away if you have kidney infection symptoms and bloody urine or nausea and vomiting.

Causes

Bacteria that enter the urinary tract through the urethra can multiply and travel to your kidneys. This is the most common cause of kidney infections.

Bacteria from an infection in another part of the body also can spread through the bloodstream to the kidneys. In rare cases, an artificial joint or heart valve that becomes infected can cause a kidney infection.

Rarely, a kidney infection happens after kidney surgery.

Risk factors

Factors that increase the risk of a kidney infection include:

Being female. The urethra is shorter in women than in men. That makes it easier for bacteria to travel from outside the body to the bladder. The urethra being close to the vagina and anus also makes it easier for bacteria to enter the bladder.

Once in the bladder, an infection can spread to the kidneys. Pregnant women are at even higher risk of a kidney infection.
Having a urinary tract blockage. Anything that slows the flow of urine or makes it harder to fully empty the bladder can raise the risk of a kidney infection. This includes a kidney stone, a narrowed urethra or an enlarged prostate gland.
Having a weakened immune system. Medical conditions such as diabetes and HIV can weaken the immune system. Certain medicines also can lower immunity. These include drugs taken after an organ transplant that help prevent rejection.
Having damage to nerves around the bladder. Nerve or spinal cord damage can block the feeling of a bladder infection. That can make it hard to know when an infection travels to a kidney.
Using a urinary catheter. Urinary catheters are tubes used to drain urine from the bladder. Catheters are sometimes used after a surgical procedure or diagnostic test. They're also used in people who are confined to a bed.
Having a condition that causes urine to flow the wrong way. In vesicoureteral reflux, small amounts of urine flow from the bladder back into the tubes that connect the bladder and kidneys. People with this condition are at higher risk of kidney infections when they're kids and when they become adults.

Complications

If left untreated, a kidney infection can lead to potentially serious complications, such as:

Kidney scarring. This can lead to chronic kidney disease, high blood pressure and kidney failure.
Blood poisoning. The kidneys filter waste from blood and return the filtered blood to the rest of the body. A kidney infection can cause bacteria to spread through the bloodstream.
Pregnancy complications. A kidney infection that occurs during pregnancy can increase the risk of having a baby with a low birth weight.

Prevention

Reduce your risk of kidney infection by taking steps to prevent urinary tract infections. Women in particular may lower the risk of urinary tract infections if they:

Drink fluids, especially water. Fluids can help remove bacteria from the body when you urinate.
Urinate as soon as you need to. Don't delay urinating when you feel the urge.
Empty the bladder after sexual intercourse. Urinating as soon as possible after sex helps clear bacteria from the urethra. This lowers the risk of infection.
Wipe carefully. Wipe from front to back after urinating and after a bowel movement. This helps prevent bacteria from spreading to the urethra.
Avoid using products in the genital area. Deodorant sprays in the genital area or douches can be irritating.

Diagnosis

To check for a kidney infection, you may be asked to provide a urine sample to test for bacteria, blood or pus in your urine. Your health care provider might also take a blood sample for a culture. A culture is a lab test that checks for bacteria or other organisms in your blood.

Other tests might include an ultrasound, a CT scan or a type of X-ray called a voiding cystourethrogram. A voiding cystourethrogram involves injecting a contrast dye to take X-rays of the bladder when full and while urinating.

Treatment

Antibiotics for kidney infections

Antibiotics are the first line of treatment for kidney infections. The drugs used and the length of time of the treatment depend on your health and the bacteria found in your urine tests.

Symptoms of a kidney infection often begin to clear up within a few days of treatment. But you might need to continue antibiotics for a week or longer. Finish taking the full course of antibiotics even if you start feeling better.

Your provider might want you to have a repeat urine culture test to make sure that the infection has cleared. If the infection is still present, you'll need to take another course of antibiotics.

Hospitalization for severe kidney infections

If your kidney infection is severe, you may need to go to the hospital. Treatment might include antibiotics and fluids through a vein in your arm. How long you'll stay in the hospital depends on how severe your infection is.

Treatment for recurrent kidney infections

An underlying medical problem such as a misshapen urinary tract can cause you to have repeated kidney infections. In that case, you might be referred to a kidney specialist (nephrologist) or urinary surgeon (urologist). You might need surgery to repair a structural problem.

Lifestyle and home remedies

To help you feel better while you recover from a kidney infection, you might:

Apply heat. Place a heating pad on your belly, back or side to ease pain.
Use pain medicine. For fever or discomfort, take a pain reliever such as acetaminophen (Tylenol, others). If you have chronic kidney disease, it's best to avoid or limit use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Motrin IB, Advil, others).
Stay hydrated. Drinking fluids will help flush bacteria from your urinary tract. Avoid coffee and alcohol until your infection has cleared. They can worsen the feeling of needing to urinate.

Preparing for an appointment

You'll likely start by seeing your family provider or a general practitioner. If your health care provider suspects that an infection has spread to your kidneys, you might need to see a specialist who treats conditions that affect the urinary tract (urologist).

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as restrict your diet for certain tests.

Take note of:

Your symptoms, including any that seem unrelated to your condition. Also note when they began.
Key personal information, including recent life changes, such as a new sex partner, and past medical history.
All medicines, vitamins and other supplements you take, including doses.
Questions to ask your provider.

Take a family member or friend along, if possible, to help you remember everything you talk about with your provider.

For kidney infection, questions to ask your health care provider include:

What is the likely cause of my kidney infection?
What tests do I need?
What treatment do you think I need?
Will there be side effects from treatment?
Do I need to go to a hospital for treatment?
How can I prevent future kidney infections?
I have other health conditions. How can I manage them together?
Are there brochures or other printed material I can have? What websites do you suggest?

Be sure to ask any other questions that occur to you during your time with your provider.

What to expect from your doctor

Your health care provider is likely to ask you questions, such as:

Have your symptoms been ongoing or on-and-off?
How bad are your symptoms?
Does anything seem to make you feel better?
What things seem to make your symptoms worse?