Horseshoe kidney is a type of congenital renal anomaly:

• congenital – the problem is present at birth
• renal – to do with the kidneys
• anomaly– different from normal.

How does horseshoe kidney happen?

While a baby is growing in the uterus (womb), the two separate kidneys normally move from the pelvis (hip area) to the flank area (just below the ribs at the back).

In horseshoe kidney, there is a variation in how this process happens. As the kidneys of the developing baby (the foetus) rise from the pelvis to the flank they join together (fuse) at the lower end of the kidneys. Instead of having two bean shaped organs, there look like one U-shaped organ. In reality this is two separate kidneys that have a join between them, but still function as if they were two separate kidneys.

Horseshoe kidneys are normally lower down in the abdomen than normal kidneys.

Does horseshoe kidney affect how the kidneys work?

Horseshoe kidneys by themselves do not usually affect how the kidneys work. They may be an incidental finding on a scan (in other words, found out by accident). It is thought that this is the case in about a third of people with horseshoe kidneys and these people will have no signs or symptoms (see symptoms below).

How common is horseshoe kidney?

Horseshoe kidney occurs in about 1 in 500 children. It is more common in boys than girls.

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