Ectopic Kidney / Renal Ectopia

What is an Ectopic Kidney?

An ectopic kidney is a congenital defect (observed at birth), where the kidney is located either below, opposite, or above the usual position. This defect occurs because the kidney of the fetus does not move to the assigned position in the course of fetal development.

Sometimes, one of the kidneys remain close to the pelvis and urinary bladder without moving upwards to the assigned position. (The pelvis is the bony lowermost part of the torso where the urinary bladder and sex organs are located.) At other times, the kidney moves excessively upwards or crosses to the opposite side and fuses with the second kidney (cross-fused renal ectopia or contralateral ectopic kidneys). Ectopic kidneys are observed at a frequency range of 1 in 500 to 1 in 110 people, while contralateral ectopic kidneys are observed at a frequency of 1 in 900 people. It is rare for both kidneys to be ectopic.

Causes of Ectopic Kidney

Ectopic kidney occurs during fetal development. Kidneys, in general, develop as outgrowths or buds within the pelvis before they move upwards to their position at the rear end of the rib cage. The upward movement of the kidney occurs between the 6^th and 9^th weeks of embryo development. ‘Ectopic’ usually refers to an organ that is out of place. When one of the kidneys remains in the pelvis, or moves upward but fuses with the second kidney, or moves higher than its normal position, an ectopic kidney is formed. Some of the causes for this defect in movement are:

• Genetic defects
• Defects in the kidney tissue that provides the signal to move upward from the pelvis
• Exposure of the pregnant mother to a drug, or a chemical, or an illness that results in defects in kidney development in the baby
• Under-developed kidney bud

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Symptoms of Ectopic Kidney

Ectopic kidneys normally go unnoticed and may be detected in adults when they undergo an examination for an unrelated reason. Patients with ectopic kidneys are sometimes predisposed to conditions such as urinary tract infection and kidney stones and may present with symptoms like fever and pain in the abdomen. Some patients suffer from vesicoureteric reflux, where the urine flows back from the bladder to the kidney, which can cause repeated infections. Other associated defects with ectopic kidney like urinary tract anomalies, reproductive system anomalies and skeletal malformations.

Diagnosis of Ectopic Kidney

Prenatal sonography can detect ectopic kidneys in the first trimester of the pregnancy. Timely diagnosis allows for regular monitoring and helps to prevent complications such as hypertension and renal failure.

Some of the diagnostic techniques for ectopic kidneys include:

Ultrasound: This procedure makes use of a transducer that directs painless sound waves to provide an image of the internal organs. This procedure may be performed in a hospital or an outpatient center.

Intravenous Pyelogram (IVP): This is an x-ray of the urinary tract, obtained following injection of a dye, which travels to the kidney and passes through the urinary tract. Thus, any structural anomalies in the urinary tract can be detected.

Radionuclide Scan: In this procedure, low doses of radioactive chemicals are injected into the patient to identify the path of the chemical in the organ of choice. Ectopic kidneys can be identified based on the location and any block in the ureters can be detected.

Magnetic Resonance Imaging (MRI): This technique uses magnets and radio waves to provide images of the internal structures of the body. A contrast dye may be used to detect the internal structures.

Voiding Cystourethrogram (VCUG): This is a procedure that utilizes a contrast dye in the bladder and the urethra. The dye is injected and the x-ray images are obtained when the bladder is full as well as when the individual urinates. The process of urination determines any issue with the bladder and urethra and if urine is regurgitating into the kidney.

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Treatment for Ectopic Kidney

In general, ectopic kidneys do not require any treatment if there are no symptoms. Associated conditions like kidney stones, urine backflow, accumulation of urine, or cross-fused kidneys require to be surgically treated.

Complications and Risks in Ectopic Kidney

Some of the risks and complications observed with ectopic kidneys are as follows:

• Kidney Stones or Calculi: Calcium and oxalate stones form in the urine based on the content in the urine.
• Trauma: When the kidney is located near the pelvis, it is susceptible to injury from an impact due to conditions, such as contact sports.
• Urinary Tract Infections: When the urine accumulates in the kidneys or there is a backflow from the bladder to the kidneys, chances of urinary infections increase.
• Hypertension: Abnormalities in kidney function can result in hypertension.

• Kidney Failure: This occurs when both the kidneys stop functioning. This is extremely rare. Generally, one kidney functions normally if the other is an ectopic kidney. When there is an accumulation of urine, the kidney fails to eliminate wastes from the blood.