Also called an ectopic kidney, it is a birth defect in which one kidney is in an abnormal position.
In most cases, people with an ectopic kidney have no complaints.
In other cases, the ectopic kidney can create urinary problems , such as urinary obstruction, infection, or urinary stones. Researchers estimate that the ectopic kidney occurs once every 1,000 births.
What are the kidneys?
The normal human body includes two kidneys. These dark red bean-shaped structures are located behind the abdominal cavity between the lower ribs and the lower back. The right kidney is slightly lower than the left.
The kidneys work to filter fluid in the body, removing toxins and waste by returning necessary substances to the blood.
They maintain the purity of fluids in the body and excrete waste and excess fluids through the urine. In addition, the kidneys help control blood pressure, produce a hormone necessary for the formation of red blood cells, and help metabolize vitamin D to its active form.
What Causes an Ectopic Kidney?
During fetal development, a baby’s kidneys first appear as buds inside the pelvis, near the bladder. As the fetus’ kidneys develop, they gradually rise to their normal position near the rib cage at the back.
Sometimes one of the kidneys cannot go up. You can stop after doing part of the climb. Or it can stay in the pelvis. Rarely does a child have two ectopic kidneys.
An ectopic kidney can stay in the pelvis near the bladder, or an ectopic kidney can cross over and fuse with the other kidney.
Some kidneys go up into the rib cage, but one can cross so that both kidneys are on the same side of the body. When a crossover occurs, the two kidneys can grow together and merge.
What are the symptoms?
An ectopic kidney may not cause any symptoms and can function normally, even though it is not in its usual position. Many people have an ectopic kidney and don’t discover it until tests are done for other reasons.
Sometimes a doctor can discover an ectopic kidney after feeling a lump in the abdomen during an exam. In other cases, an ectopic kidney can cause abdominal pain or urinary problems.
What are the possible complications of an ectopic kidney?
When a kidney is out of its normal position, there are likely drainage problems. Sometimes urine can even flow backward from the bladder to the kidney, a problem called vesicoureteral reflux, or simply reflux. The abnormal flow of urine can set the stage for a number of problems.
Normally, the urine stream kills bacteria and prevents them from growing in the kidneys and urinary tract. When a kidney is out of its normal position, urine can get trapped in the ureter or kidney. Urine that remains in the urinary tract gives bacteria a chance to grow and spread.
Symptoms of a urinary tract infection include:
- Frequent or painful urination.
- Back or abdominal pain
- Fever and chills
- Cloudiness and unusual odor in the urine.
Urinary stones are formed from substances found in the urine, such as calcium and oxalate. Urine that stays in the urinary tract too long increases the risk that these substances have time to form stones.
Symptoms of urinary stones include:
- Extreme pain in the back, side, or pelvis.
- Blood in the urine.
- Fever or chills
- Burning when urinating.
If urine backs up to the kidneys, kidney damage can occur. As a result, the kidneys cannot filter waste and excess fluid from the blood.
Symptoms of kidney failure include:
- Swelling in the legs or abdomen.
- Feeling tired.
If total kidney failure occurs, you will need dialysis or a kidney transplant. Total kidney failure occurs only when both kidneys are damaged. An ectopic kidney, even when it has no function, will not cause kidney failure.
If the ectopic kidney is in the lower abdomen or pelvis, it may be susceptible to blunt trauma injury. People with an ectopic kidney who wish to participate in body contact sports may wish to wear protective equipment.
How is the diagnosis obtained?
Your doctor can get the most information about your condition by looking at pictures of the ectopic kidney.
Several different imaging tests are available.
During an ultrasound exam, a medical technician will slide a device called a transducer across your skin, either on the side, abdomen, or pelvis, depending on the location of the kidney.
The transducer sends harmless sound waves into your body. The sound waves bounce off your kidney and return to the transducer. The computer reads the sound waves and creates a black and white image of the kidney on a television screen.
Your doctor may use standard x-ray equipment to perform an intravenous pyelogram (IVP) or voiding cystourethrogram (VCUG).
In an IVP, a special dye is injected into a vein, usually in the arm. The radiologist takes a series of snapshots as the dye circulates through the blood and reaches the kidneys. The structures of the kidneys show up on X-rays as the dye is filtered from the blood and passes through the kidneys to the ureters.
An IVP can show if urine is backing up into the ectopic kidney. In children, ultrasounds are usually done instead of IVP.
In a VCUG, a thin hollow tube called a catheter is placed into the bladder so that it can be filled with X-ray contrast material. X-rays are then taken while the patient urinates. The VCUG provides information about the bladder and reveals whether urine backs up into the kidneys when urinating.
In a nuclear scan, a small amount of a radioactive drug is injected into a vein and pictures of the kidney are taken over a period of time after the injection. Sometimes a diuretic medicine is also given to increase urine flow.
This test can reveal if the ureters – tubes that drain urine from the kidneys – are blocked and how well the kidneys are working. Sometimes a nuclear scan can be done to find the location of an ectopic kidney.
Computed tomography (CT)
A CT scan uses multiple x-ray images to create a cross-sectional view of your body on a computer screen. You will lie on a table that passes through a donut-shaped machine where the scan is done.
CT scans are generally not needed in the evaluation of an ectopic kidney, but can be done in some cases.
Magnetic resonance imaging (MRI)
MRI technology uses radio waves and magnets to create images of internal organs. No radiation exposure is required. With most MRI machines, you lie on a table that slides into a tunnel that may be open or closed at one end.
Some newer machines are designed to allow you to be in a more open space. Like CT scans, MRI scans are rarely needed to evaluate an ectopic kidney.
In addition to imaging tests, your doctor may order blood tests to determine how well your kidneys are working. These tests are almost always normal in patients with an ectopic kidney, even if it is severely damaged, because the other kidney usually has completely normal function.
What are the treatments for an ectopic kidney?
If your urinary function is normal and the doctor finds no obstruction, no treatment for the ectopic kidney is needed. Your doctor should continue to monitor your condition in case a change occurs.
If tests show obstruction, you may need surgery to correct the position of the kidney to allow better drainage of urine. To correct reflux, the surgeon may reposition the ureter in the bladder so that urine cannot flow back into the kidney.
If extensive kidney damage has occurred, the surgeon may need to remove the kidney. As long as the other kidney is working properly, losing one kidney is not a problem.
Many people live normal lives after donating a kidney for transplant. Some people are even born with only one kidney and lead full and healthy lives without discovering its condition.
With the right tests and treatment, if needed, an ectopic kidney shouldn’t cause serious long-term health problems.
Hope through research
Researchers from universities and government agencies are working to understand the causes of kidney and urinary tract birth defects and to find more effective and preventative treatments.