Pyelonephritis (pie-low-ne-FRY-tis) is an infection in one or both kidneys. Pyelonephritis happens when urine (pee) infected with bacteria flows up from the bladder or when an infection in the bloodstream reaches the kidneys.

More to Know

A kidney infection like pyelonephritis is similar to a bladder infection, as they are both urinary tract infections (UTIs). However, children are usually sicker with fever, back pain, or vomiting with pyelonephritis.

Keep in Mind

Pyelonephritis requires medical attention. A doctor will ask for a urine sample, and may order other tests, to determine the cause and best treatment. It's important to treat kidney infections with a full course of antibiotics. Untreated and repeat infections can lead to high blood pressure and kidney disease in adulthood.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.