Megaureter: a dilated ureter

What is megaureter?

The ureter is a thin tube that carries urine from the kidney to the bladder. In children its diameter is usually less than 5 mm. When the ureter’s diameter is more than 7 mm, it is called megaureter. The dilation often occurs together with dilation of the renal pelvis, that is, with hydronephrosis.

Types

Megaureter is divided into four groups by cause:

• Obstructive. Where the ureter enters the bladder there is a narrow, non-functioning segment, and urine cannot flow down. This is the most common type.
• Refluxing. Urine flows back from the bladder and dilates the ureter. This is assessed as vesicoureteral reflux.
• Both obstructive and refluxing. This is uncommon.
• Neither obstructed nor refluxing. Although the ureter is wide, urine flows normally. It often corrects itself.

In addition, megaureter is primary (a defect of the ureter itself) or secondary (for example, as a result of posterior urethral valves or neurogenic bladder). In secondary megaureter, the underlying cause must be treated.

Symptoms

Today, most megaureters are found by ultrasound during pregnancy, and there are no complaints after birth. In cases not found earlier, the first sign is often a febrile urinary tract infection. Older children may also have abdominal pain, blood in the urine or kidney stones.

Diagnosis

• Ultrasound: the diameter of the ureter, especially behind the bladder, the renal pelvis and the kidney tissue.
• VCUG (voiding cystourethrogram): to check for reflux and look at the urethra. It is almost always needed in megaureter.
• MAG3/DTPA: kidney function and how well urine drains.

Treatment

Monitoring and antibiotic prophylaxis

Most primary obstructive megaureters improve as the child grows. So the first step is active monitoring: ultrasound is repeated periodically, and MAG3/DTPA is done when needed. In the first months, a low daily dose of antibiotic (prophylaxis) is often recommended to reduce the risk of infection.

When is surgery needed?

• kidney function drops,
• the dilation increases,
• febrile infections keep coming back despite prophylaxis,
• pain or stones develop.

The standard operation is reattaching the ureter to the bladder (reimplantation): the narrow segment is removed, the dilated ureter is tapered when needed, and it is attached to the bladder using a tunnel technique that prevents reflux. The success rate is above 90%.

In babies under one year this operation is technically difficult, so when needed temporary methods are chosen: endoscopic widening of the narrow segment with placement of a stent, or temporarily bringing the ureter out to the skin. These protect the kidney until the child grows.