Discussion of Megaureter
- Megaureter is a generic term indicating the presence of an enlarged ureter with or without concomitant dilatation of the upper collecting system.
- Primary megaureter is a term that includes all cases of megaureter due to an idiopathic congenital alteration at the vesicoureteral junction.
- There are three major categories of primary megaureter:
- Obstructed primary megaureter: Dilatation above a short, aperistaltic, normal-caliber juxtavesical section of a normally inserted ureter. Somewhat similar to achalasia and Hirschsprung disease.
- Refluxing primary megaureter: Caused by a short or absent intravesical ureter, congenital paraureteric diverticulum, or other derangement of the vesicoureteral junction
- Nonrefluxing unobstructed primary megaureter: Ureter is dilated beginning at a point just above the bladder. The cause of this phenomenon is unknown.
- Secondary megaureter occurs as a result of some abnormality involving the bladder or urethra (eg, posterior urethral valves, neuropathic bladder, urethral strictures, ureteroceles, acquired causes of obstruction).
- Primary nature of megaureter must be confirmed by excluding secondary causes such as posterior urethral valves or neuropathic bladder.
- In obstructed primary megaureter, VCUG demonstrates no vesicoureteral reflux. US shows hydronephrosis and ureteral dilatation above the persistently narrowed distal aperistaltic segment.
- In primary megaureter, once VUR has been excluded, perfusion studies and diuresis renography are indicated to differentiate dilatation that is functionally obstructive and requires surgical treatment from dilatation that represents a variant in normal ureteral development and can be conservatively treated initially.
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 References for Megaureter
- Teresa Berrocal, Pedro López-Pereira, Antonia Arjonilla, and Julia Gutiérrez. Anomalies of the Distal Ureter, Bladder, and Urethra in Children: Embryologic, Radiologic, and Pathologic Features. RadioGraphics 2002 22: 1139-1164.