Megaureter

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 cystogram 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 reimplantation 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 ^[1]

• Incidence : rare (<0.5 cases per 1000 births) ^[2]
• Sex : ♂> ♀ (4: 1) ^[3]
• Occurrence: second most common cause of hydronephrosis in newborns (20% of cases) ^[2]

Epidemiological data refers to the US, unless otherwise specified.

Primary megaureter

• Primary obstructed megaureter
  1. Congenital developmental defect of the muscular layer of the terminal ureter
  2. Distal aperistaltic segment of ureter causing functional obstruction
  3. Increased intraureteral pressure in dilation
• Primary refluxing megaureter: dilation of the ureter secondary to primary vesicoureteral reflux (VUR)

Secondary megaureter

• Secondary obstructed megaureter
  • Bladder outlet obstruction
  • High intracystic pressure
  • Functional obstruction of the vesicoureteral junction (VUJ)
  • Urine can not pass into the bladder
  • Ureteral dilation
• Secondary refluxing megaureter : bladder outlet obstruction with ureteral dilation caused by secondary vesicoureteral reflux

References:^[4]

• Prenatal detection of hydronephrosis and dilated ureter on antenatal ultrasonography
• Postnatal presentation
  • ∼ 50% are asymptomatic, with normal renal parameters
  • Often an incidental finding on ultrasound ^[5]
  • Symptoms of urinary tract infection
  • Abdominal / flank pain
  • Features of uremia

• Ultrasound: best initial and confirmatory test
  • Hydronephrosis
  • Ureteral dilation > 7 mm
• Further evaluation
  • Voiding cystourethrography (VCUG): to identify retrograde reflux of urine into the ureters
  • Radionuclide renal scanning : to identify obstruction and evaluate renal function

Primary megaureter

• Conservative therapy
  • Indicated in children with preserved renal function
  • Prophylactic antibiotics
  • Regular follow-up
• Surgery
  • Indicated in children with deteriorating renal function
  • Procedure: resection of the distal segment of the ureter and re-implantation into the bladder (ureteroneocystostomy)

Secondary megaureter

• Treatment of the underlying disease

• Urinary tract infections
• Hydronephrosis
• Obstructive nephropathy

We list the most important complications. The selection is not exhaustive.