Horseshoe kidney in children

What is a horseshoe kidney?

Normally the two kidneys lie separately, one on each side of the spine. Sometimes, while a baby develops in the womb, the kidneys join at their lower ends and form a single U-shaped organ that looks like a horseshoe. This is called a horseshoe kidney.

It is the most common way for kidneys to be fused. In one study based on X-ray imaging, it was found in about 1 in every 670 people. It is more common in boys than in girls. The fused kidney usually sits a little lower than normal kidneys and closer to the front of the belly.

Most children have no symptoms, so a horseshoe kidney is usually found on an ultrasound.

What can it come with?

Children with a horseshoe kidney are more likely to have:

• UPJ obstruction: a narrowing where the kidney’s collecting area (the renal pelvis) joins the tube to the bladder, causing hydronephrosis,
• vesicoureteral reflux: urine flowing back from the bladder toward the kidney,
• urinary tract infections,
• kidney stones.

In one study of children who had symptoms, more than half had reflux or UPJ obstruction.

A horseshoe kidney can occur together with some genetic syndromes, especially Turner syndrome in girls and Edwards syndrome (trisomy 18). About one in three children also has another congenital difference of the heart and blood vessels, nervous system or genitourinary system.

Symptoms

When there are symptoms, they may include:

• belly pain and nausea,
• fever and pain when peeing (with an infection),
• blood in the urine.

Tests

The first test is a kidney and bladder ultrasound. It shows whether the renal pelvis is widened or there are stones, and it also checks the bladder. Urine and blood tests check for infection and show how well the kidneys work.

If there is dilation or an infection with fever, the doctor may order more tests: a voiding cystourethrogram (VCUG) to look for reflux, and a MAG3 scan to check whether urine drains properly. Not every child needs these tests.

Treatment and follow-up

The shape of a horseshoe kidney cannot be changed, and there is no need to change it. A child without symptoms or related problems needs no treatment; the doctor may suggest follow-up ultrasounds.

Treatment targets the related problem. Infections, stones and reflux are each treated in the usual way. If UPJ obstruction affects how the kidney works, a pyeloplasty is done. This is the most common operation in children with a horseshoe kidney, and the results are usually good.

Daily life and sports

Because the fused kidney sits low and close to the front of the belly, it is more easily injured by a blow. Ask the doctor whether contact sports are suitable for your child.

When to see a doctor

If a child with a horseshoe kidney has a fever, belly or side pain or blood in the urine, or is peeing much less than usual, do not wait for the next scheduled visit; see a doctor.