Kidney infection (pyelonephritis) is a specific type of urinary tract infection (UTI) that generally begins in your urethra or bladder and travels up into your kidneys. If not treated properly, kidney infection can permanently damage your kidneys or spread to your bloodstream and cause a life-threatening infection. Prompt medical attention is required.

Your urinary system is composed of your kidneys, ureters, bladder and urethra. All play a role in removing waste from your body. Your kidneys filter waste from your blood, adjust blood levels of many substances, and conserve or excrete water from your system depending on your body's needs. Tubes called ureters carry urine from your kidneys to the bladder, where it's stored until it exits your body through the urethra. Kidney infection usually begins when bacteria enter the urinary tract through the urethra and then start to multiply. Kidney infection can occur through your bloodstream, although this is rare.

Antibiotics are the typical treatment for kidney infection. You can take a number of steps to help prevent a kidney infection in the first place.

Signs and symptoms

Kidney infection may cause one or more of these signs and symptoms:

• Frequent urination
• Strong, persistent urge to urinate
• Burning sensation or pain when urinating
• Abdominal pain or pressure
• Cloudy urine with a strong odor
• Pus or blood in your urine (hematuria)
• Inability to urinate (urine retention)
• Need to urinate during the night (nocturia)
• Back, side (flank) or groin pain
• Fever

Severe kidney infection also may involve:

• High fever — body temperature of 101 F (38.3 C) or greater
• Shaking chills
• Night sweats
• Extreme fatigue
• Nausea or vomiting
• Confusion

In infants and young children, signs and symptoms of kidney infection may include:

• Irritability
• Loss of appetite
• Loose bowel movements
• New episodes of bed-wetting (enuresis)

In older adults, mental changes, such as confusion, sometimes are the only signs of kidney infection.