Megaureter is defined as ureteral dilation > 7 mm. Primary megaureter is due to obstructed or refluxing vesicoureteral junction, while secondary megaureter is caused by bladder outlet obstruction. Although rare, primary megaureter is responsible for up to 20% of hydronephrosis cases in neonates. About half of the patients with megaureter are asymptomatic. The other half may present with a urinary tract infection, abdominal pain, or features of uremia. Ultrasound (prenatal and postnatal) shows ureteral dilation, which may be accompanied by hydronephrosis. CT or MR urography shows a constricted terminal ureter with proximal dilation, while voiding cysticrogram detects vesicoureteral reflux in refluxing megaureter. Prophylactic antibiotics and regular follow-ups are sufficient in patients with primary megaureter and preserved renal function. Surgery (terminal ureter resection and re-implantation into the bladder) is indicated in patients with deteriorating renal parameters. Patients with secondary megaureter require treatment of the underlying cause. Those who do not receive treatment can develop recurrent urinary tract infections, hydronephrosis, and obstructive nephropathy with permanent kidney damage.
- Ureteral dilation > 7 mm in children 
- Incidence : rare (<0.5 cases per 1000 births) 
- Sex : ♂> ♀ (4: 1) 
- Occurrence: second most common cause of hydronephrosis in newborns (20% of cases) 
Epidemiological data refers to the US, unless otherwise specified.
- Primary obstructed megaureter
- Primary refluxing megaureter: dilation of the ureter secondary to primary (VUR)
- Secondary obstructed megaureter
- Secondary refluxing megaureter : bladder outlet obstruction with ureteral dilation caused by secondary
Ultrasound: best initial and confirmatory test
- Ureteral dilation > 7 mm
- Further evaluation
- Indicated in children with preserved renal function
- Prophylactic antibiotics
- Regular follow-up
- Treatment of the underlying disease
We list the most important complications. The selection is not exhaustive.