Mega cystis

This was a 19  year old primi with history of consanguinity.The scan was done in the first trimester.
A large cystic mass was made out in the lower abdomen.


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Fetal megacystis refers to the presence of an unusually large bladder in a fetus. It is generally defined as a

  • bladder diameter > 7 mm in the first trimester 3
  • bladder diameter > 30 mm in the second trimester 
  • bladder diameter > 60 mm in the third trimester 


The estimated incidence of antenatal imaging is at ~ 1 : 1500 pregnancies.


It can result from a number of causes but with the main underlying mechanism being either a distal stenosis of reflux.


Associated anomalies are common and include

  • posterior urethral valves
  • chromosomal anomalies
    • on a first trimester scan ( 10 – 14 weeks)
      • if the longitudinal bladder diameter of 7 – 15 mm there is a risk of a chromosomal defects is esimated at ~ 25% 
      • if the bladder diameter is > 15 mm the risk of chromosomal defects is estimated at ~ 10% 4
  • oligohydramnios
  • megacystis microcolon intestinal hypoperistalsis (MMIH) syndrome (Berdon syndrome)
  • megacystis megaureter syndrome
  • prune belly syndrome
  • Radiographic assessment

    Antenatal ultrasound

    Will show an enlarged bladder

    Ancilliary sonographic findings

    Treatment and prognosis

    The overall prognosis can be variable from progressive obstruction to spontaneous resolution. A follow-up ultrasound is necessary to correctly interpret the significance of megacystis detected in the first trimester

    If the fetus is chromosmally normal and there is megacystis on the 1st trimester scan

    • there is spontaneous resolution of the megacystis in about 90% of cases when the 1sttrimester longitudinal bladder diameter is between 7 – 15 mm 4.
    • if the bladder diameter is > 15 mm there is a very high likelihood  of associated with progressive obstructive uropathy 4

    Management will depend on the underlying pathology

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