Fetal hyperechogenic bowel has been described as a normal finding and as a sign of cystic fibrosis, chromosomal aneuploidy, or fetal infection.1–5 Its etiology remains unknown. We present evidence that in some cases, hyperechogenic bowel can be associated with intra-amniotic bleeding.
Materials and Methods
We monitored 28 fetuses with visible intra-amniotic bleeding after intrauterine blood transfusions between 24 and 35 weeks' gestation. Nineteen transfusions were done between 24 and 28 weeks' gestation, seven between 23 and 31 weeks' gestation, and two after 32 weeks' gestation. All of the fetuses required transfusions for fetal anemia due to isoimmunization (anti-D in 22 cases, anti-Kell in four cases, and anti-C in two cases). All of the intrauterine fetal transfusions were done with sterile technique and continuous sonographic guidance with an Acuson XP-128 (Acuson Inc., Mountain View, CA) equipped with 3.5 MHZ and 5 MHZ curvilinear and linear transducers. A 20-gauge needle was used for the procedures. Twenty-one intra-uterine transfusions required one needle puncture, six required two, and one required three. Placentas were anterior in 15 women, posterior in nine, and fundal in four. Postpuncture bleeding was identified when a stream of echogenic material from the cord into the amniotic space was seen, lasting at least 60 seconds. In the case with the longest duration of bleeding, brisk bleeding was noted for 40 seconds, followed by dripping of blood for another 50 seconds. Comprehensive fetal ultrasound examinations were done before and 12 hours after all blood transfusions. Follow-up ultrasound examinations were done weekly. Hyperechogenic bowel was diagnosed when the echogenicity of fetal bowel was similar to that of bone.
None of the fetuses had echogenic bowel before the initial transfusions. Intra-amniotic bleeding was followed by bowel echogenicity in seven of 28 (25%) fetuses within the first 12 hours after the bleeding episodes. Echogenic bowel persisted in five fetuses (18%) 2 weeks after the bleeding, and it was still seen in three fetuses (11%) 4 weeks later. Seven of 28 fetuses required repeat transfusions within 4 weeks; however, none of the repeat transfusions were accompanied by excessive intra-amniotic bleeding. Figures 1 through 3 show the sonographic appearance of the bowel in one of the studied fetuses.
Our MEDLINE search of the English literature (using search terms “echogenic bowel,” “intra-amniotic bleeding,” “ultrasonography,” “fetal hemolytic disease,” and “in utero transfusion”) over the past 10 years found the first report that suggested an association between intra-amniotic bleeding and fetal echogenic bowel to be that of Sepulveda et al.6 Among 726 women who underwent second-trimester amniocentesis, 20 (3%) had bloodstained amniotic fluid and 12 (2%) had brown amniotic fluid. Echogenic bowel was detected in 10% of fetuses with blood-stained fluid, in 25% with dark brown fluid, and in 2% with clear amniotic fluid 2–4 weeks after the amniocentesis. The authors concluded that an echogenic appearance of the fetal bowel might be caused by the swallowing of blood in the amniotic fluid. Bowel echogenicity was not assessed before amniocentesis in any of their cases.
We studied a group of fetuses who had intra-amniotic bleeding during intravascular transfusions for accepted clinical indications. The fetal bowels appeared normal before the episodes of intra-amniotic bleeding. Bowel echogenicity was first detected within 12 hours after the invasive procedures in seven (25%) fetuses and remained for 2 weeks in five (8%) of them. Four weeks after transfusions, echogenic bowel was still seen in three (11%) fetuses. The timing of echogenic bowel relative to a documented episode of intra-amniotic bleeding seems to indicate a causal relationship; however, not all fetuses with intra-amniotic bleeding developed echogenic bowel. Sepulveda et al6 speculated that the amount of blood ingested by the fetus, the gestational age at the time of bleeding, and the speed at which blood is cleared from the amniotic fluid might affect the onset of echogenic bowel.
In another study, Sepulveda et al7 examined the presence of heme pigments in 104 normal pregnancies and 14 pregnancies in which amniocentesis was done because of echogenic bowel. They concluded that echogenic bowel was associated with the presence of heme pigments in amniotic fluid. They suggested that further studies were required to clarify the pathogenesis of echogenic bowel associated with intra-amniotic bleeding. We believe that the results of the current study indicate that intra-amniotic bleeding is one of the possible causes of echogenic fetal bowel.
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