Sonography of normal fetal bowel.

This is a prospective study of the sonographic appearance of normal small bowel and colon in 300 fetuses. Normal fetal bowel can be frequently seen during sonographic examination. The diameter of the lumen of the small bowel and colon increases as gestational age increases. The fetal small bowel lumen rarely exceeds 6 mm in diameter, and fetal colon lumen diameter rarely exceeds 23 mm. Small bowel peristalsis can be seen with increasing frequency with increasing gestational age. Colon peristalsis is not seen. Haustral folds in the colon can be frequently demonstrated. Meconium in the colon always remains hypoechoic relative to the fetal liver and bowel wall. Hyperechoic appearance of the small bowel in early gestation and cystic appearance of parts of the colon in later gestation may mimic pathology. Normal herniation of bowel into umbilical cord can be seen in early (8 to 11 weeks) gestation.