Megaureter
The vast majority of children are born with urinary tracts that are normal in appearance and function normally efficiently. But in some infants, megaureters, an abnormal widening of the connecting tube between the kidneys and bladder, can cause infections and obstructions, and possibly serious kidney damage if the problem is not diagnosed and treated. But what are the symptoms? The information below should give you a head start about this potentially serious health hazard.
What are megaureters?
The ureters are tube-like structures in the body that carry or propel urine from the kidneys to the bladder. While the normal width of a child's ureter is three to five millimeters (mm.), a megaureter is a tube that is greater than 10 mm. (three-eighths of an inch) in diameter hence the term "megaureter" ("large ureter"). Certain conditions produce this abnormal widening. The condition of megaureter can result from an abnormality of the ureter itself (primary) or from conditions related to the bladder obstruction (secondary).
What are the different types of megaureters?
Most megaureters are classified as the following:
- primary obstructed megaureter: A distinct anatomical blockage where the ureter enters the bladder. This obstruction of the ureter then causes the abnormal widening of the ureter. The obstruction can produce damage to the kidney over time. This condition, when accurately diagnosed, is likely to require surgical repair for its correction and relief of obstruction. Even though the problem may improve with time, diligent follow up is necessary.
- refluxing megaureters: These ureters are wide because of abnormal backward flow of urine (vesicoureteral reflux) up the ureters from the bladder. Normally, once that urine is in the bladder, it should not go back up the ureters. Refluxing megaureters are an extreme presentation of vesicoureteral reflux, and can be seen more commonly in newborn males. In some of these patients, the degree of reflux, and widening of the ureters, can improve over the first year of life. Persistently refluxing megaureters require surgical correction by a procedure termed ureteral reimplantation, and by possibly tapering or surgically narrowing the caliber of the ureters. The condition of refluxing megaureters may be linked to the condition known as "megacystis megaureter syndrome," a condition where the bladder, instead of emptying completely, is enlarged due to cycling of urine between it and the ureters via reflux.
- non-obstructive, non-refluxing megaureters: These are wide ureters not caused by obstruction or urine backflow. Many of these improve with time. Accurate evaluation of these wide ureters is necessary to exclude both obstruction and reflux as the causes of the widening.
- obstructed, refluxing megaureters: An obstructed ureter that also suffers from reflux. A dangerous combination since the ureters gets bigger and more blocked with time.
- secondary megaureters: These enlarged ureters appear in association with other conditions such as posterior urethral valves, prune belly syndrome and neurogenic bladder.
What are the symptoms of megaureter?
In the past, the majority of megaureters were found during the evaluation of a child with a urinary tract infection. These patients usually experience fever, back pain and vomiting.
But today, because of the widespread use of prenatal fetal sonography, more megaureters are discovered as prenatal hydronephrosis or dilatation of the urinary tract in the fetus.
Because megaureters can cause a severe infection or obstruction that leads to kidney damage, this health issue is potentially serious. Dilatation of the urinary tract may imply a blockage or obstruction, but that is not always the case. In some situations, a dilated ureter may not affect the kidney at all. Also, most patients with prenatally detected megaureters do not experience symptoms related to this wide ureter, but evaluation is necessary to assure that there is no potential compromise of kidney function which may later produce symptoms.
How is a megaureter diagnosed?
If your child develops a urinary tract infection, or other symptoms that could signal this condition, check with your doctor. Further investigation is warranted. You can expect the urologist to conduct a series of tests to clarify the anatomy and function of the urinary tract. They include:
ultrasound: Also known as sonography, this simple and painless imaging test is usually done to evaluate the appearance of the kidney, ureter and bladder. The study is highly sensitive in detecting widened ureters. In fact, while sonography rarely picks up normal ureters because of their narrowed size, this technology produces excellent images of dilated ones.
voiding cystourethrogram (VCUG): A VCUG is done to determine if vesicoureteral reflux is occurring. A small catheter is inserted through the urethra into the bladder and a contrast dye is injected into the bladder before X-rays are taken. If reflux is present, the image will show the contrast produced by the backflow into the ureter.
diuretic renal scans: Used to evaluate for a possible obstruction, this test is performed by injecting a radioactive substance into a vein, which is then carried to the kidneys. While the study yields data about a possible blockage, it also gives physicians information about the organ's function.
intravenous pyelogram (IVP): Also referred to as excretory program, IVP is performed by injecting dye into a vein and taking X-ray pictures of the abdomen as the dye is emptied from the kidneys. While renal scans have replaced IVP in evaluating dilated urinary tracts, this test can be extremely helpful in questionable cases.
Magnetic resonance of the urinary tract (MR-U): this evolving technology produces excellent imaging of the urinary tract, much more accurately than IVP’s, and may become the most anatomically sensitive imaging study of the urinary tract for conditions such as megaureters It also involves injecting dye and imaging the urinary tract using magnetic resonance technology. Its use in small children is limited because of the need for sedation or possibly general anesthesia.
How is a megaureter treated?
If tests reveal an obstruction or impaired kidney function, your child may need surgery to correct the problem. The typical operation for megaureters is called ureteral reimplantation and ureteral tapering, the technical term urologists use for inserting the ureters back into the bladder and for trimming the widened ureter. Unless the child has a urinary tract infection or decrease in kidney function, the surgery can be delayed until 12 months of age. Surgery in infants is technically demanding and such should be performed by individuals experienced with neonatal surgery. Many babies are kept on antibiotic prophylaxis during this period of observation to minimize the likelihood of infections.
During the procedure, the surgeon makes an incision in the lower abdomen and, depending on the child's anatomy, approaches the ureter through either the bladder (transvesical) or from outside the bladder (extravesical). The ureter is disconnected from the bladder, and if very wide, it may need to be trimmed (tapered) and then replaced in the bladder. If an obstruction exists, it is removed. Your child may have a catheter for a few days to improve healing. Hospitalization is usually between two and four days.
Currently, most symptomatic megaureters are best treated by this open type of surgery where the blockage is removed (for obstructed megaureters), the efflux is corrected (for refluxing megaureters) and possibly the ureters are trimmed (for very wide ureters). Minimally invasive technologies such as injection of substances to correct reflux or laparoscopy for ureteral reimplantation are not currently applicable for megaureters.
What can be expected after treatment for a megaureter?
Several weeks after surgery, some of the tests that were done before surgery may need to be repeated to determine the success of the surgery. The size of the ureter may not improve immediately after surgery, so evaluation over time will be necessary to ensure a good outcome. Potential complications of surgery are bleeding, obstruction of the ureter and persistent or new vesicoureteral reflux. Obstruction may occur soon after the operation or after a longer period of time. Fortunately, this complication occurs in only 5 percent of cases and it may require additional surgery. Vesicoureteral reflux complication may occur after surgery in 5 percent of the cases and may improve with time. Most patients are followed for a number of years, using ultrasound, to ensure that the appearance of the kidney and ureter continues to improve. A renal scan is often done to assure that function is preserved or improved, and that obstruction is corrected, and a VCUG is often obtained a few months after surgery to assure that reflux is not present.
Frequently asked questions:
Is this condition genetic?
At this time scientists do not know if there are genetic links.
Is surgery always necessary to correct a megaureter?
No. Some megaureters may improve over time without the need for surgery. However, it is important to prevent infections during the time of observation so antibiotics are usually prescribed.
Is minimally-invasive surgery an option?
It may be possible to place a stent or catheter through the blocked portion of the megaureter as a temporary procedure to improve the drainage of the kidney. Laparoscopic techniques are not presently well developed to correct most megaureters but that may change in the future.
Are there long-term problems if we do not do anything?
Possibly yes. They include ureteral stones, urinary tract infection, deterioration of kidney function and back pain.
Links for additional information:
American Academy of Pediatrics, Section on Urology
Reviewed: January 2011
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