Symptoms & Causes of Kidney Infection (Pyelonephritis)

What are the symptoms of a kidney infection?

Symptoms of a kidney infection may include fever and chills, frequent or painful urination, and nausea or vomiting.

Symptoms of kidney infections vary by age and may include

• fever and chills
• cloudy, dark, bloody, or foul-smelling urine
• frequent, painful urination
• pain in your back, side, or groin
• nausea or vomiting

Children younger than age 2 years with a kidney infection may only have a high fever. They may also show signs of feeding difficulty and poor weight gain.

When should I seek a health care professional’s help?

Seek care right away if you have kidney infection symptoms. Although uncommon, a kidney infection could lead to sepsis, which can be life threatening.

Symptoms of sepsis may include

• fever and chills
• confusion
• rapid breathing and heart rate
• severe pain or discomfort
• shortness of breath

What causes a kidney infection?

Bacteria in your upper urinary tract are often the cause of kidney infections. Viruses are a less common cause.

Most kidney infections start as a bladder infection in your lower urinary tract. Bacteria that live in your bowel can get into your urinary tract and cause an infection. If a bladder infection isn’t treated or doesn’t go away, it can spread to one or both kidneys.

Normally, the body keeps bacteria in the urinary tract in balance. Emptying your bladder, or urinating, is one way the body helps keep a healthy number of bacteria in your bladder.

In some cases, your blood may carry harmful bacteria or viruses from another part of your body to your kidneys. Rarely, you might get a kidney infection after surgery.