Kidney Abnormalities: How They Develop and Where They Are Located

The kidneys are the organs in your body that filter the blood and make urine (pee). A person is typically born with two kidneys. One kidney is located on the left side of the body, and one is on the right side.  Both kidneys are usually about the same size. They are typically located in the middle part of the belly and toward the back. The kidneys then connect to long tubes called ureters. These tubes go down toward the lower part of the belly and drain into the bladder, which is the “tank” that holds urine.

There can be many differences in how the kidneys develop and where they are located.

There are two main groups of kidney abnormalities: how the kidney develops within the womb and differences in shape and location.

Differences in How the Kidneys Develop

There are 3 main differences you can see with how the kidney develops within the womb:

• Renal Agenesis is what it’s called when a person only has one kidney. It can be a single right kidney or a single left kidney. A person can have normal kidney function even if they have only one kidney.
• Renal Hypoplasia is the name of the condition when one or both kidneys are smaller than expected. A kidney with hypoplasia usually does not work the same as a normal kidney.
• Renal Dysplasia is what it’s called when the kidney forms abnormally. This can include kidneys that have cysts within them (which are like sacs of fluid in the kidney). Kidneys with dysplasia may work normally or may not work the same as a normal kidney.

Differences in Shape and Location of the Kidneys

There are also multiple differences that can be seen in the shape and position of the kidneys. The 3 most common types are ectopic kidneys, horseshoe kidneys and cross fused kidneys.

When a kidney is not located in the usual position, it is called an ectopic kidney. It can be located higher or lower than the usual position, or lower in the belly, in the pelvic area.

Horseshoe Kidney occurs when the lower parts of each kidney connect in the midline and are in the lower part of belly (pelvic area). Because the lower parts of each kidney are connected, they look like one kidney that is shaped like a horseshoe.

When both kidneys are located on the same side (meaning that one has “crossed over” to the other side) rather than one on each side, it is called a crossed fused ectopia. These kidneys may or may not be connected.

Children who have these abnormalities may need other teams to be part of their care. Many times, children with renal agenesis, renal hypoplasia and renal dysplasia will have pediatric nephrology take part in their care. Pediatric nephrologists are the medical kidney doctors who can help keep track of kidney function. They often monitor kidney function by different types of blood tests. Sometimes either nephrology or urology may recommend different types of x ray tests that are used to help evaluate kidney function.

Children who have differences in the shape or position of the kidneys do not necessarily need to see pediatric nephrology, as kids with these abnormalities may not have any problem with the function of the kidneys. Kids with differences in the shape or position of the kidneys are typically followed with renal ultrasounds to makes sure that they kidneys are growing properly. Renal ultrasounds can be monitored by either urology or nephrology.