Syndrome composed of classic triad of findings

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  Renal cystic dysplasia in 95-100%

  
  
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  Encephalocele or other central nervous system (CNS) abnormality in 90%

  
  
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  Postaxial polydactyly in 55-75%

Should have at least 2 of 3 classic features

Renal cystic dysplasia most consistent finding

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  Kidney appearance is variable

  
  
  
  
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    Most commonly grossly enlarged and echogenic but may be filled with macroscopic cysts

  
  
  
  
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  Renal size often massive, causing enlarged abdominal circumference

Occipital encephalocele classic CNS finding (60-80%) but may have other malformations

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  Dandy-Walker malformation, microcephaly, holoprosencephaly, anencephaly

Diagnosis can be made in 1st trimester

Severe oligohydramnios or anhydramnios by 2nd trimester

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  Makes evaluation of polydactyly and other more subtle findings difficult

Trisomy 13: Significant overlap in imaging features

Oligohydramnios leads to pulmonary hypoplasia

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  Most stillborn or die within few hours

Autosomal recessive with 25% recurrence risk for future pregnancies

May first present with increased nuchal translucency

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  Use endovaginal US to search for anomalies if suspicious findings or positive family history

When 1 finding seen (especially enlarged kidneys), carefully search for others