HYPERECHOIC BOWEL

Hyperechoic bowel is fetal bowel which is as bright, or brighter than, the surrounding bone when viewed by ultrasound.  Although there is a good chance this ultrasound finding is a normal variant, hyperechoic bowel has been associated with certain problems in the pregnancy.

Hyperechoic bowel can occur as a result of maternal bleeding in the uterus.  The baby may swallow the blood, which makes the bowel appear bright on ultrasound.  If this is the cause for the echogenic bowel, an ultrasound can be performed to try to locate the source of maternal bleeding.  Usually, bleeding will resolve and cause no further reason for concern.  Hyperechoic bowel may also be due to a gastrointestinal malformation resulting in an obstruction in the fetus' bowel. In such cases, surgery is required after delivery.

Two maternal infections associated with fetal hyperechoic bowel are cytomegalovirus (CMV) and toxoplasmosis.  CMV and toxoplasmosis can cross the placenta and infect the fetus, which may cause the appearance of echogenic bowel on ultrasound. When hyperechoic bowel is seen on ultrasound, the risk that the baby has an infection is approximately 3%.  Most women who are infected with one of these viruses do not experience any symptoms, or they may have non-specific cold-like symptoms.  The mother's blood can be tested for CMV and toxoplasmosis antibodies, and the baby can be tested if an amniocentesis sample is available.  If the baby is found to have an infection, routine ultrasound is recommended to monitor for complications. 

Chromosome abnormalities, particularly Down syndrome , are associated with hyperechoic bowel.  Fetal hyperechoic bowel is considered an ultrasound “marker”, which increases the chance that the baby has a chromosome abnormality to approximately 3%.  Down syndrome is a sporadic chromosome abnormality, caused by an extra chromosome. Chromosomes are the inherited structures in the cells of the body.  Chromosome abnormalities involving a missing or extra chromosome are not usually inherited and are not caused by an exposure during pregnancy.  Instead, they are caused by random events in cell division at the time of conception and can occur in anyone’s pregnancy.  Individuals with Down syndrome have an extra #21 chromosome, thus three rather than two copies of chromosome 21.  It is this extra genetic material that causes the features of Down syndrome, including mental retardation, a characteristic facial appearance, and other health problems.  We can test the baby for chromosome abnormalities by amniocentesis.
 
Cystic fibrosis (CF) is a hereditary disease that can cause the appearance of echogenic bowel on ultrasound.  There is approximately a 4% risk for the fetus to have CF when hyperechoic bowel is seen.  CF affects the normal function of the lungs and pancreas.  It is a recessive disease.  Therefore, in order to be affected, a child must inherit an abnormal CF gene from each parent who themselves are healthy, but carriers of the gene.  When each parent is a CF carrier, the risk their child will be affected with the disease is 25% (1 in 4).  Carrier testing for CF is available and is an option when fetal echogenic bowel is noted on ultrasound.  If both parents are found to be CF carriers, the baby can be tested for CF by amniocentesis.

Hyperechoic bowel is sometimes associated with abnormal function of the placenta (placental insufficiency).  The placenta provides nutrient-rich blood from the mother to the fetus to allow for normal growth and development.  Therefore, placental insufficiency can lead to growth and developmental delays, and other pregnancy complications.  The risk for abnormal placental function is increased when hyperechoic bowel is seen in association with an elevated maternal serum AFP (alpha-fetoprotein).

Cases in which no specific cause of the hyperechoic bowel is identified will be followed with increased surveillance in the third trimester to monitor for possible growth delay and other pregnancy complications.

It is important to remember that hyperechoic bowel is often a normal variant that has no effect on the baby. 


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