Ectopic Kidney

An ectopic kidney is a birth defect in which a kidney is located in an abnormal position within the body. In most cases, people with an ectopic kidney have no complaints, but a pelvic kidney may complicate pregnancy. In other cases, the ectopic kidney may create urinary problems, such as urine blockage, urinary tract infection, or urinary stones. Researchers estimate that ectopic kidney occurs once in every 1,000 births.^[1]

Kidneys are bean-shaped organs, each about the size of a fist. Most people have two kidneys located near the middle of the back, just below the rib cage. The kidneys filter wastes and extra fluid from the blood. The wastes and extra fluid become urine, which drains from the kidneys to the bladder through tubes called ureters. Urine is stored in the bladder until it is released from the body during urination.

Other Names

An ectopic kidney may also be referred to as a pelvic kidney. The condition may be described as renal ectopia.

Symptoms

An ectopic kidney may not cause any symptoms and may function normally, even though it is not in its usual position. Many people have an ectopic kidney and do not discover it until they have tests done for other reasons. A radiographic survey of symptom-free potential transplant donors found ectopic kidneys in 2 of 151 individuals.^[2] Sometimes, a doctor may discover an ectopic kidney after feeling a lump in the abdomen during an examination. In other cases, an ectopic kidney may cause abdominal pain or urinary problems.

Drawing of bladder, ureters, and kidneys. The kidney on the right of the picture is normally positioned. The kidney on the left is an ectopic kidney. Source: NIH

Causes

During fetal development, a baby's kidneys first appear as buds inside the pelvis, near the bladder. As the fetal kidneys develop, they climb gradually toward their normal position near the rib cage in the back. Sometimes, one of the kidneys fails to make the climb. It may stop after making part of the climb. Or it may remain in the pelvis. Rarely does a child have two ectopic kidneys. Several theories attempting to pinpoint the cause of ectopic kidneys rely on animal models of the disease and experiments done on samples taken from humans with the condition.^[3]

Anatomic drawing of bladder, ureters, and fused kidneys. The kidney that would normally be on the left side of the picture has crossed over and fused with the kidney on the right. Source: NIH

Some kidneys climb toward the rib cage, but one may cross over so that both kidneys are on the same side of the body. When a crossover occurs, the two kidneys may grow together and become fused.

Diagnosis

Doctors sometimes use blood tests to determine how well the kidneys are working. These tests are almost always normal in patients with an ectopic kidney, even if it is badly damaged, because the other kidney usually has completely normal function. Thus, doctors get the most information by looking at pictures of the ectopic kidney. Several different imaging tests are available.

Ultrasound

In an ultrasound, examination, a medical technician glides a device called a transducer over the skin—either of the side, the abdomen, or the pelvis—depending on the location of the kidney. The transducer sends harmless sound waves into the body. The sound waves bounce off the kidney and back to the transducer. The equipment reads the sound waves and creates an image of the kidney. Ultrasound is routinely used to evaluate patients after nonpenetrating abdominal injuries and sometimes detects ectopic kidneys.^[4]

X-Ray

A doctor may use conventional x-ray equipment to perform an intravenous pyelogram (IVP) or a 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 the x-rays as the dye is filtered from the blood and passes through the kidneys to the ureters. An IVP can show whether urine is backing up into the ectopic kidney. In children, ultrasounds are usually done instead of IVPs.

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 as the patient urinates. The VCUG gives information about the bladder and reveals whether urine is backing up toward the kidneys during urination.

Nuclear scan

In a nuclear scan, a small amount of a radioactive drug is injected into a vein, and pictures are taken of the kidney over a period of time after the injection. Sometimes a diuretic medicine is also given to increase urine flow. This test can reveal whether the ureters—tubes that drain urine from the kidneys—are blocked and how well the kidneys work. Sometimes, a nuclear scan may be done to find the location of an ectopic kidney.

Computerized tomography

A Computed Tomography (CT): Questions and Answers|computerized tomography (CT) scan uses multiple x-ray images to create a cross-section view of the body on a computer screen. The patient lies on a table that passes through a doughnut-shaped machine where the scanning takes place. CT scans are not usually needed in the evaluation of an ectopic kidney, but they may be done in a few cases.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) technology uses radio waves and magnets to create pictures of internal organs. No exposure to radiation is required. With most MRI machines, the patient will lie on their back on a table that slides into a tunnel. The tunnel may be open-ended or closed at one end. Some newer machines are designed to allow the patient to lie in a more open space. Like CT scans, MRIs are rarely needed to evaluate an ectopic kidney.

Treatment

No treatment is needed for an ectopic kidney if urinary function is normal and the doctor finds no blockage. However, these cases are monitored closely for any change.

If tests show that obstruction is present, surgery may be necessary to correct the position of the kidney to allow for better drainage of urine. To correct reflux, the surgeon may reattach the ureter to the bladder so that urine can not reflux into the kidney.

If extensive kidney damage has occurred, the kidney is often removed. As long as the other kidney is working properly, losing one kidney is not a problem. Many people live a normal life after donating a kidney for transplant. Some people are even born with only one kidney and lead full, healthy lives without discovering their condition.

Living With Ectopic Kidney

With the right testing and treatment, if needed, an ectopic kidney should cause no serious long-term health problems.

Related Problems

When a kidney is out of the normal position, drainage problems are likely. Sometimes, urine can even flow backwards from the bladder to the kidney, a problem called vesicoureteral reflux, or simply reflux. Abnormal urine flow can set the stage for a number of problems.^[5]

Infection

Normally, urine flow washes out bacteria and keeps them from growing in the kidneys and urinary tract. When a kidney is out of the normal position, urine may get trapped in the ureter or in the kidney itself. Urine that remains in the urinary tract gives bacteria the chance to grow and spread. Symptoms of an urinary tract infection include frequent or painful urination, back or abdominal pain, fever, and chills. The urine may be cloudy or have an unusual smell.

Stones

Urinary stones form from substances found in the urine, such as calcium and oxalate. Urine that remains too long in the urinary tract increases the risk that these substances will have time to form stones. Symptoms of urinary stones include the following:

• extreme pain in the back, side, or pelvis
• blood in the urine
• fever or chills
• vomiting
• burning during urination

Kidney failure

If urine backs up all the way to the kidneys, damage to the kidneys can occur. As a result, the kidneys can not filter wastes and extra fluid from the blood. Symptoms of this kidney failure include swelling in the legs or abdomen, feeling very tired, headaches, or nausea. If total kidney failure occurs, dialysis or a kidney transplant is necessary. Total kidney failure happens only when both kidneys are damaged. One ectopic kidney, even when it has no function, will not cause kidney failure.

Trauma

If the ectopic kidney is in the lower abdomen, or pelvis, it may be susceptible to injury from blunt trauma. Protective gear while playing sports can protect against the risk of trauma to the ectopic kidney.

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 treatments. Through its Pediatric Urology Program, the National Institute of Diabetes and Digestive and Kidney Diseases funds research into bladder and urinary tract development. Additionally, the National Institute of Child Health and Human Development has established the Birth Defects Initiative to study the genetic and molecular mechanisms underlying the developmental processes of the fetus.

References

1. ↑ Malek RS, Kelalis PP, Burke EC. Ectopic kidney in children and frequency of association with other malformations. Mayo Clin Proc. 1971 Jul;46(7):461-7. Citation
2. ↑ Frick MP, Goldberg ME. Uro- and angiographic findings in a "normal" population: screening of 151 symptom-free potential transplant donors for renal disease. AJR Am J Roentgenol. 1980 Mar;134(3):503-5. Abstract | PDF
3. ↑ Pope JC 4th, Brock JW 3rd, Adams MC, Stephens FD, Ichikawa I. How they begin and how they end: classic and new theories for the development and deterioration of congenital anomalies of the kidney and urinary tract, CAKUT. J Am Soc Nephrol. 1999 Sep;10(9):2018-28. Abstract | Full text | PDF
4. ↑ Brenchley J, Sloan JP, Thompson PK. Echoes of things to come. Ultrasound in UK emergency medicine practice. J Accid Emerg Med. 2000 May;17(3):170-5. Abstract | PDF
5. ↑ Cinman NM, Okeke Z, Smith AD. Pelvic kidney: associated diseases and treatment. J Endourol. 2007 Aug;21(8):836-42. Abstract

External Links

American Society of Pediatric Nephrology

American Urological Association Foundation

March of Dimes

National Institute of Child Health and Human Development