Pyelonephritis

Learn the causes and how to treat a kidney infection.

What is pyelonephritis?

Pyelonephritis is an infection of one or both kidneys. (Kidneys filter water and waste from your blood). It differs from a urinary tract infection (UTI) in that it involves the kidneys rather than the bladder alone.

The infection is usually caused by bacteria that often start in the bladder (which stores your urine) and may spread to the kidneys. Treatment involves taking antibiotics for one to two weeks.

Typically, there are no lasting effects, but if treatment is delayed, pyelonephritis can lead to kidney damage, kidney failure, or a life-threatening infection.

Most common symptoms

Pro Tip

The degree of fever is important. The higher the fever, the more severe the illness. Feelings of general malaise can also be a sign of the severity of illness. —Dr. Steve Mindrup

Pyelonephritis can cause fever and chills, intense shivering, and pain in the back and sides (called the flank region).

You may also have symptoms of a UTI, which is an infection of the bladder and the urethra, the tube that expels urine.

Main symptoms

Pyelonephritis symptoms

  • Fever and chills, sometimes with intense shivering.
  • Back, side, groin, and/or abdominal pain.

UTI symptoms

Other symptoms you may have

  • Nausea and vomiting.
  • Fatigue.
  • General weakness.
  • Diarrhea.

Risk factors

You have an increased risk of a kidney infection if you have certain health conditions.

  • Conditions that lead to abnormal kidney anatomy or function, such as polycystic kidney disease, horseshoe kidney, and vesicoureteral reflux.
  • Diseases that weaken the immune system, such as diabetes, cancer and some cancer treatments, HIV infection, and sickle cell disease.
  • Procedures or devices on the urinary tract such as catheters (a tube that collects urine) and recent surgery.
  • Conditions that cause urinary obstruction (urinary tract is blocked), like large kidney stones, enlarged prostate, and nerve damage that prevents urination.

Pyelonephritis is more common in the following groups:

  • Women
  • Infants
  • Pregnant women
  • Elderly people
  • People with suppressed immune systems

Next steps

If you have symptoms of a UTI, you should call your doctor or go to urgent care.

Go to the ER or call 911 if you have:

  • Persistent high fevers
  • Uncontrollable shivering
  • Persistent pain
  • Difficulty urinating
  • Severe nausea that prevents you from eating or drinking

Pyelonephritis in children

Children can also get pyelonephritis, and many of the symptoms are the same as in adults. In addition, new or increased bedwetting can be a sign of a UTI in a child.

Young children with a kidney infection may have very little energy, be irritable (especially when having to urinate), or lose their appetite. Call your pediatrician or go to the ER if you notice any of these symptoms.

Do not give your child aspirin or NSAIDs like ibuprofen without asking a doctor. These NSAIDs can affect kidney function so when that function is compromised by the infection, the combination can damage the kidney.

What causes pyelonephritis?

Pro Tip

Recurrent pyelonephritis can be a result of kidney stones or poorly draining kidneys. More testing may be needed to assess for underlying conditions. —Dr. Mindrup

Pyelonephritis is most commonly caused by bacteria, the most common of which is Escherichia coli (E. coli), which is found in the intestines but can enter the urinary tract through the urethra. In rare instances, it can also be caused by a fungus, like Candida.

The infection usually reaches the kidneys by coming up through the urinary tract: from the urethra to the bladder and up through the ureter (a tube that connects the bladder to the kidney).

It can also occur from bacteria moving directly from the colon to the bladder in a phenomenon called translocation. Occasionally, a kidney infection results from an infection in the bloodstream.

How is pyelonephritis diagnosed?

Your doctor will ask you some questions about your symptoms and medical history. You will provide a urine culture, which will be tested for bacteria, fungus, and white blood cells (a sign your body is fighting an infection).

Dr. Rx

Patients with chronic back pain often attribute it to their kidneys. So pyelonephritis is often overdiagnosed as a source of back pain. True kidney pain is typically not a chronic condition—it is usually so severe that it requires treatment immediately. —Dr. Mindrup

What is the best treatment for pyelonephritis?

Most kidney infections are caused by bacteria and are treated with antibiotics for 1 to 2 weeks. (For fungal infections, you will be given an antifungal medication). The exact medication you take depends on the severity of your illness, which bacteria are most common where you live, and your laboratory test results.

In mild cases, you can take your prescription medications at home. If severe or you are elderly, you might be admitted to the hospital and given medication through an IV (intravenous) line until you start feeling better. Then, you can be switched to oral medication once symptoms stabilize.

If you have pyelonephritis because of a condition that weakens the immune system or because of a urinary obstruction, that condition will also be treated.

Follow up

Always take the full course of medications that are prescribed. Call your doctor if your symptoms return again. You should also call your doctor if you feel better, but your symptoms have not fully gone away.

Prevention

The best way to prevent a kidney infection is to try to avoid UTIs. You can do this by drinking plenty of water to stay hydrated. Practice good urinary hygiene as well:

  • Wipe from front to back after using the bathroom.
  • Keep your genitals clean.
  • Urinate after sex.
  • Avoid holding in your urine when you feel like you have to urinate.
  • Keep bowel movements soft and regular by plenty of fluid intake and high fiber diet with exercise.
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