Echogenic fetal bowel

Echogenic fetal bowel is an observation in antenatal ultrasound imaging, in which fetal bowel appears to be brighter than it is supposed to be. It is a soft marker for trisomy 21 and has several other associations. When observed, it needs to be interpreted in the context of other associated abnormalities.

The estimated incidence is reported to range from 0.2-1.8% in second trimester fetuses. 

The cause of echogenic fetal bowel is uncertain, although it has been postulated that it is related to loss of water from meconium. Note that meconium can become echogenic in the third trimester. It may also be caused by intra-amniotic haemorrhage, which is subsequently swallowed by the fetus.

It may be most commonly seen in the right lower quadrant of the fetus.

Associations

Echogenic bowel can be a normal variant / isolated finding in up to ~70% of cases 6,12.

Recognised associations include:

Antenatal ultrasound

To be truly 'echogenic bowel' it must be brighter than bone (e.g. femur, spine), and this should be demonstrated on an image with appropriate gain settings. Tissue harmonic imaging and compound imaging should also be switched off.

A sonographic grading system exists to assess the degree of echogenicity, although this is not commonly used in clinical practice.

  • grade 0: isoechoic to liver
  • grade 1: mildly hyperechoic to liver or less than bone
  • grade 2: moderately hyperechoic compared to liver or as echogenic as bone
  • grade 3: markedly hyperechoic compared to liver or greater than bone

If there is difficulty discerning whether bowel is as echogenic as bone, one can progressively decrease the image gain to see which structure disappears first.

Isolated echogenic bowel is associated with a normal outcome in 75% of cases.

Workup of this finding should include, where available, an ultrasound study to assess for any associated anomalies, referral to genetic counselling, TORCH serology, cystic fibrosis carrier testing, and offer of amniocentesis. 

Imaging differential considerations include:

  • falsely increased bowel echogenicity due to a high transducer frequency (especially when 8 MHz is used instead of 5 MHz 4)
  • in the 3rd trimester, meconium containing bowel may appear echogenic as a normal finding 10
  • meconium peritonitis: coarse calcifications, pseudocysts
Ultrasound - obstetric
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Article Information

rID: 1256
Section: Signs
Synonyms or Alternate Spellings:
  • Increased antenatal bowel echogenicity
  • Increased fetal bowel echogenicity
  • Hyperechogenic fetal bowel
  • Hyperechoic fetal bowel

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