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What is Horseshoe Kidney (Renal Fusion)?

Horseshoe Kidney
Horseshoe Kidney
Image © 2003 Fairman Studios, LLC.

Most people are born with 2 kidneys. But sometimes the kidneys form fused together. The information here will help you talk to your urologist if you or your child has this condition.

Horseshoe kidney occurs in about 1 in 500 children. It occurs during fetal development as the kidneys move into their normal position. With horseshoe kidney, as the kidneys of the fetus rise from the pelvic area, they become attached (“fuse”) together at the lower end or base. By fusing, they form into a U shape, like a horseshoe. This is thought to happen more often in males than in females.

What Happens Under Normal Conditions?

The urinary tract is the body’s drainage system. It includes two kidneys, two ureters, a bladder, and a urethra.

Male Urinary Tract
Male Urinary Tract
Medical Illustration Copyright © 2015 Nucleus Medical Media, All rights reserved

Female Urinary Tract
Female Urinary Tract
Medical Illustration Copyright © 2015 Nucleus Medical Media, All rights reserved

Healthy kidneys work day and night to clean our blood. These 2 bean-shaped organs are found near the middle of the back, just below the ribs. One kidney sits on each side of the spine.

Our kidneys are our body’s main filter. They clean about 150 quarts of blood daily. Every day, they form about 1-2 quarts of urine by pulling extra water and waste from the blood. Urine normally travels from the kidneys down to the bladder and out through the urethra.

As a filter, the kidney controls many things to keep us healthy:

  • Fluid balance
  • Electrolyte levels (e.g., sodium, potassium, calcium, magnesium, acid)
  • Waste removal in the form of urine
  • The regulation of blood pressure and red blood cell counts

When the kidneys are damaged or when a tumor grows, they may not function well. In most cases, some damage won’t cause too many problems. But, major damage may require more treatment, like dialysis.

As a child develops in the mother’s uterus, the kidneys form first in the child’s lower belly. They slowly move up to their final position on both sides of the spine as they develop.