How does ectopic kidney happen?

Most people have two kidneys which each have a single tube (ureter) that connects to the bladder. This tube drains urine from the kidneys into the bladder.

Early on in pregnancy, while a baby is growing in the uterus (womb), the baby’s kidneys start to develop in their pelvis. As the baby continues to grow, the kidneys move up and turn inwards to reach their normal position in the middle of the back on either side of the spine (backbone), near the bottom edge of the ribs.

If this movement does not happen as it should, the kidney does not reach its normal position. This is known as an ectopic kidney.

An ectopic kidney can occur in different positions.

• The kidney may stay within the pelvis (pelvic kidney)
• It may move upwards but stop lower than the normal position
• It may move higher than its normal position
• It may cross to the other side of the body (crossed renal ectopia).

Sometimes the top part of the kidney that is ectopic joins (is fused to) the bottom part of the kidney that is in the normal position. This is called crossed fused renal ectopia. The joined kidneys still function as if they were two separate kidneys.

How common is ectopic kidney?

It is thought that around 1 in 1,000 to 1 in 5,000 babies are born with an ectopic kidney.

Does ectopic kidney affect how the kidneys work?

If a kidney is in an abnormal position, it does not usually affect how the kidneys work. However, an ectopic kidney is slightly more likely than a kidney in the normal position to have other problems with the urinary tract.

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