Pyelo­nephritis: kidney infection in children

What is pyelonephritis?

Pyelonephritis happens when bacteria travel up the urinary tract, reach the kidney and cause inflammation of the kidney tissue. It is the most serious form of urinary tract infection and almost always comes with fever.

In infants, it is one of the most common bacterial causes of fever without a clear source.

Signs

• fever above 38°C, sometimes with chills,
• in infants: irritability, poor feeding, vomiting, lethargy; sometimes fever is the only sign,
• in older children: flank or back pain, abdominal pain, nausea,
• burning when urinating, frequent urination, foul-smelling urine.

Diagnosis

• Urinalysis and culture from a correctly collected sample (how to collect it),
• blood tests: markers of inflammation and, in severe cases, kidney function,
• ultrasound: the kidneys, dilation of the urinary tract, abscess or obstruction.

Treatment

Antibiotics are started right after diagnosis, without waiting for the culture result. They are then changed according to the culture result when needed.

• Children who are stable and can take medicine by mouth are usually treated at home with oral antibiotics.
• Young infants and children who are very unwell or vomiting are admitted to the hospital for intravenous antibiotics, then switched to oral medicine once they improve.
• The total duration is usually 7–10 days.
• Plenty of fluids, fever reducers.

Fever usually comes down within 24–48 hours. If it doesn’t, the child should be examined again.

Follow-up tests

In a child who has had pyelonephritis, it is important to find the cause and protect the kidney:

• Ultrasound: for every child after the first febrile infection.
• VCUG (voiding cystourethrogram): to check for reflux, when the ultrasound is abnormal, infections recur or the course is atypical.
• DMSA: to look for kidney scarring, 4–6 months after the infection.

Kidney scarring

In some children, the inflamed area of the kidney heals with a scar. If the scar is small, it usually causes no problems. Large or bilateral scars can lead to high blood pressure and reduced kidney function years later. That is why children with kidney scars have their blood pressure and urine checked periodically.