Isolated echogenic bowel diagnosed on second-trimester ultrasound
Isolated echogenic bowel diagnosed on second-trimester ultrasound is a transient, idiopathic finding in approximately 0.5% of fetuses. When identified, an experienced provider should perform a detailed fetal anatomic survey, and consideration should be given to evaluation for fetal aneuploidy and genetic abnormalities.
Diagnosis/definition: Diagnosis is made when the fetal bowel displays an echogenicity or brightness equal to or greater than that of surrounding fetal bone, typically the iliac wing. If echogenic bowel is suspected, the ultrasound gain should be turned down to the lowest setting at which bone still appears white. If the fetal bowel continues to have an echogenic appearance, the diagnosis can be made.
Epidemiology/Incidence: Echogenic bowel is a nonspecific finding observed during 0.2% to 1.8% of routine second-trimester ultrasound exams.
Risk factors/associations: The differential diagnosis for the most common etiologies for echogenic bowel includes: intra-amniotic bleeding, fetal cystic fibrosis, fetal aneuploidy (e.g. trisomy 21, 13, 18), congenital infection (e.g. cytomegalovirus, other viruses, toxoplasmosis), and primary gastrointestinal pathology (e.g. obstruction, atresia, perforation). The estimated incidence of these conditions is highly variable, due in part to the relatively small sample sizes studied and the subjective component of the diagnosis of echogenic bowel. The estimated incidence of aneuploidy in fetuses with isolated echogenic bowel ranges from 3.3-16%, with trisomy 21 being the most commonly diagnosed aneuploidy in this population.
Complications: The presence of echogenic bowel on fetal ultrasound, both when isolated and when present in combination with other anomalies, has been associated with intrauterine growth restriction and intrauterine fetal demise.
Screening/Work-up: The finding of echogenic bowel on second-trimester ultrasound should prompt a detailed ultrasound examination in search for other anomalies. If there is a normal 4-chamber view and the outflow tracts are visualized as normal, then a fetal echocardiogram is not necessary. However, if these views are abnormal or not obtainable, a fetal echocardiogram should be performed. Amniocentesis should be offered to all patients irrespective of the presence or absence of associated anomalies, given that echogenic bowel is present as an isolated finding in 4-25% of fetuses with aneuploidy. Amniotic fluid should be sent for fetal karyotype as well as polymerase chain reaction for the most common congenital infections, such as CMV. For patients who decline invasive testing, maternal IgG and IgM titers for CMV can be drawn. If unknown, parental cystic fibrosis carrier status also should be determined. A suggested algorithm for the evaluation of fetuses with echogenic bowel is shown in Figure 2.
Prenatal care: Serial evaluation of fetal growth by ultrasound assessment should be performed.
Antepartum testing: Although antenatal testing can be considered, its utility remains controversial in the management of isolated echogenic bowel unless fetal growth restriction or other indications develop.
Last Reaffirmed: Feb 1, 2013