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% of 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 hemorrhage, which is subsequently swallowed by the fetus.
It is most commonly seen in the right lower quadrant of the fetus.
Echogenic bowel can be a normal variant / isolated finding in up to ~70% of cases 6,12.
Recognized associations include:
intra-amniotic hemorrhage: with subsequent swallowing of blood products
- this is considered one of the commonest causes of an echogenic fetal bowel, and it may occur after an amniocentesis or placental abruption
- trisomy 21 (~15%) 12
- intrauterine cytomegalovirus infection: (~15%) 5,12
- detects 2-11% of cystic fibrosis cases 11,12
- may have a higher association if there is concurrent bowel dilatation
- intrauterine growth restriction (IUGR): (~5%) 12
intrauterine fetal demise (IUFD): ~9 x increased risk
- particularly if serum alpha-fetoprotein levels are also elevated 7
- some data suggests that echogenic bowel occurs before 30 weeks, when there is subsequent IUFD 6
- meconium peritonitis 16
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 15, although this is not commonly used in clinical practice.
- grade 0: isoechoic to liver
- grade 1: mildly hyperechoic to the liver or less than bone
- grade 2: moderately hyperechoic compared to the liver or as echogenic as bone
- grade 3: markedly hyperechoic compared to the 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.
Treatment and prognosis
An 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 counseling, 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
- 1. Johnson PT, Kurtz AB. Obstetric and gynecologic ultrasound, case review. Mosby Inc. (2001) ISBN:0323008607. Read it at Google Books - Find it at Amazon
- 2. Weissleder R, Wittenberg J, Harisinghani MG. Primer of diagnostic imaging. Mosby Inc. (2003) ISBN:0323023282. Read it at Google Books - Find it at Amazon
- 3. Nyberg DA, Dubinsky T, Resta RG et-al. Echogenic fetal bowel during the second trimester: clinical importance. Radiology. 1993;188 (2): 527-31. Radiology (abstract) - Pubmed citation
- 4. Vincoff NS, Callen PW, Smith-bindman R et-al. Effect of ultrasound transducer frequency on the appearance of the fetal bowel. J Ultrasound Med. 1999;18 (12): 799-803. J Ultrasound Med (abstract) - Pubmed citation
- 5. Al-kouatly HB, Chasen ST, Streltzoff J et-al. The clinical significance of fetal echogenic bowel. Am. J. Obstet. Gynecol. 2001;185 (5): 1035-8. doi:10.1067/mob.2001.117671 - Pubmed citation
- 6. Goetzinger KR, Cahill AG, Macones GA et-al. Echogenic bowel on second-trimester ultrasonography: evaluating the risk of adverse pregnancy outcome. Obstet Gynecol. 2011;117 (6): 1341-8. doi:10.1097/AOG.0b013e31821aa739 - Free text at pubmed - Pubmed citation
- 7. Al-kouatly HB, Chasen ST, Karam AK et-al. Factors associated with fetal demise in fetal echogenic bowel. Am. J. Obstet. Gynecol. 2001;185 (5): 1039-43. doi:10.1067/mob.2001.117641 - Pubmed citation
- 8. Iruretagoyena JI, Bankowsky H, Heiser T et-al. Outcomes for fetal echogenic bowel during the second trimester ultrasound. J. Matern. Fetal. Neonatal. Med. 2010;23 (11): 1271-3. doi:10.3109/14767050903551442 - Pubmed citation
- 9. Scioscia AL, Pretorius DH, Budorick NE et-al. Second-trimester echogenic bowel and chromosomal abnormalities. Am. J. Obstet. Gynecol. 1992;167 (4 Pt 1): 889-94. - Pubmed citation
- 10. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
- 11. Agathokleous M, Chaveeva P, Poon LC et-al. Meta-analysis of second-trimester markers for trisomy 21. Ultrasound Obstet Gynecol. 2013;41 (3): 247-61. doi:10.1002/uog.12364 - Pubmed citation
- 12. Bahado-Singh R, Morotti R, Copel JA et-al. Hyperechoic fetal bowel: the perinatal consequences. Prenat. Diagn. 1995;14 (10): 981-7. Pubmed citation
- 13. Ameratunga DM, Said JM, Reidy K et-al. Perinatal outcomes following the ultrasound diagnosis of echogenic bowel: an Australian perspective. Fetal. Diagn. Ther. 2012;31 (3): 179-84. doi:10.1159/000336123 - Pubmed citation
- 14. De Oronzo MA. Hyperechogenic fetal bowel: an ultrasonographic marker for adverse fetal and neonatal outcome?. J Prenat Med. 2012;5 (1): 9-13. Free text at pubmed - Pubmed citation
- 15. Slotnick RN, Abuhamad AZ. Prognostic implications of fetal echogenic bowel. Lancet (London, England). 347 (8994): 85-7. Pubmed
- 16. Wolfgang Dähnert. Radiology Review Manual. (2011) ISBN: 9781609139438
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