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Megaureter

Megaureter

Programs that treat this condition

Kidney Transplant Program

What is Megaureter?

Megaureter is a descriptive term that means a "large" or "big" ureter. The ureter is a tubular structure with a small cavity that serves as a conduit for the flow of urine from the kidney to the bladder. See Urinary Tract Anatomy. There is one for each of the two kidneys. Together, the ureter and the kidney collecting system are referred to as the upper urinary tract. There are several different causes (discussed below) of an enlarged ureter and the condition can involve the kidneys.

What causes a megaureter?

There are several causes of megaureter. One cause is a congenital maldevelopment in which the distal ureter, which is normally a muscular layer of tissue, is replaced by stiff, fibrous tissue. In the absence of a muscular layer, normal peristalsis (worm-like movement of the ureter that propels urine towards the bladder) cannot occur. High grade vesicoureteral reflux is another cause of a megaureter.

How is megaureter diagnosed?

Many infants and children with megaureter have no symptoms. With increasing frequency this condition is detected on prenatal ultrasound. However in other cases, a child may be referred to a pediatric urologist or pediatric surgeon after experiencing at least one of the following symptoms during infancy or early childhood:

abdominal mass that can be seen or felt
acute pain in the back or abdomen
febrile urinary tract infection
blood in the urine (hematuria)
urinary incontinence
urolithiasis (stone formation within the urinary tract).

If it is determined that your child has megaureter, doctors must look for what's causing it and the cause will dictate the course of treatment. So if your child has been referred to a specialist and megaureter is suspected, you should expect a complete evaluation of the entire urinary tract. Megaureter may first be detected during an initial evaluation that includes an ultrasound of the kidneys, ureters and bladder. Other studies are usually needed to confirm the diagnosis and to determine the cause. These tests may include:

intravenous pyelogram (IVP), which allows doctors to visualize the anatomy of the ureter and assess how well the kidneys collect and drain urine. The IVP also allows doctors to estimate ureteral diameter. In general, megaureter is a ureter with a diameter of greater than seven to ten millimeters.
voiding cystourethrogram (VCUG) a specialized x-ray that is used if the doctor suspects that vesicoureteral reflux (backward flow of urine from the bladder to the ureter and/or kidney) is causing the problem. Vesicoureteral reflux is responsible for the ureteral dilation in a significant proportion of patients with megaureter.
A renal (kidney) scan (MAG 3 with lasix) is used if the doctor suspects that an obstruction at the ureterovesical junction is causing the problem. This scan provides very sensitive quantitative information regarding kidney function and drainage characteristics. Along with the IVP, it is particularly helpful in identifying and assessing the degree of blockage in this kind of obstruction.
Evaluation for both vesicoureteral reflux and obstruction allows doctors to place your child's megaureter or dilated upper urinary tract into one of the four following categories:

Evaluation for both vesicoureteral reflux and obstruction allows doctors to place your child's megaureter or dilated upper urinary tract into one of the four following categories:

refluxing megaureter: vesicoureteral reflux alone is responsible for the dilation
obstructed megaureter: a significant degree of blockage alone is present at the ureterovesical junction (UVJ)
refluxing and obstructed megaureter: both vesicoureteral reflux and blockage at the UVJ are present
nonrefluxing and nonobstructed megaureter: dilation of the upper urinary tract is present but no evidence of reflux or clinically significant obstruction is documented during evaluation.

Even after the cause of your child's megaureter is determined, the doctor may want to perform additional tests to get a more complete characterization of kidney and bladder function. Specialized renal scans (MAG 3 or DMSA) and/or laboratory (blood and urine) testing may be performed to assess kidney function. The doctor may also want to take a baseline serum creatinine level. This provides a gross estimation of kidney function and is essential for initial evaluation and follow up care, particularly for patients with bilateral megaureters.

Specific evaluation of bladder function (urodynamics) may also be helpful for optimizing care of children with megaureter(s). Urodynamic evaluation assesses bladder storage and emptying functions. This allows for appropriate and optimal medical and, at times, surgical management of problems identified within the bladder itself that may be partly responsible for megaureter development.

How is megaureter treated?

How the doctor chooses to manage your child's megaureter, will depend quite specifically on what is causing the problem and the severity and character of the symptoms. In some cases of megaureter, where no or only minimal reflux or obstruction is present, the problem usually resolves on its own. Simple observation as an outpatient with periodic ultrasound examination may be all that is required. In some mild cases that involve vesicoureteral reflux or obstruction the doctor may also prescribe a daily prophylactic antibiotic in order to decrease the risk of urinary tract infection. Spontantaneous resolution of the ureteral dilation or vesicoureteral reflux can occur early or later on (sometimes years) into follow up.

In other mild cases, your doctor may continue urodynamic study, which may be helpful in guiding management. For example, medication may be necessary for treatment of specific bladder dysfunction. This may in turn increase the chance for spontaneous resolution of either reflux or obstruction.

Patients with a more severe grade of reflux or obstruction may suffer from recurrent urinary tract infections while on prophylactic antibiotics (breakthrough infections), or persistent vesicoureteral reflux or obstruction. These patients may require surgical intervention, typically in the form of ureteral reimplantation. Ureteral reimplantation is a procedure in which surgeons eliminate the obstruction by disconnecting the ureter from the bladder, removing the blockage and then reimplanting the ureter back in its natural position.

Surgery is performed with general anesthesia and it begins with a transverse incision in the lower abdominal wall followed by opening of the anterior wall of the bladder. In severely affected urinary tracts with massively dilated ureter(s) and/or kidney(s), reconstructive surgery may be helpful in preventing renal deterioration. This may include narrowing of the distal dilated ureteral segment prior to reimplantation.

Whether or not surgery is required, your child's doctor will want to keep an eye on your child's condition for years to come. Long-term follow up care for your child is essential because it allows for prevention and/or management of any future problems that can be associated with your child's condition, including urinary tract infections or any associated bladder dysfunction and/or renal function impairment.

Comprehensive initial and long-term evaluation, coupled with appropriate, directed management and aggressive follow up of all children with megaureter is critically important for optimal outcome. The goal is to identify the problem, treat it proactively, and evaluate any impact it may have on the upper and/or lower urinary tract over time.


					Children's Hospital Boston is the primary pediatric teaching hospital of Harvard Medical School

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