Physiological gut herniation
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Physiological gut herniation is a natural phenomenon that occurs in early pregnancy. It usually occurs from around 6-8 weeks until 12-13 weeks in utero, after which the bowel returns to the abdominal cavity.
It occurs as a result of the bowel (particularly ileum) growing faster than the abdominal cavity during the early gestational period. In the physiological situation, the intestine elongates and moves outside of the embryonic abdomen herniating into the base of the umbilical cord. This occurs at ~8 weeks gestational age and is due to a number of factors including rapid growth of the cranial end of the midgut (which will form the small intestine), and the large size of the developing liver and kidneys. While the bowel is within the umbilical cord, the midgut rotates 90° counter-clockwise (facing the embryo). At approximately 10-11 weeks the abdomen enlarges and the intestines return to the abdominal cavity. The midgut then rotates an additional 180° counter-clockwise, fixing to the posterior retroperitoneum.
presence of fetal bowel outside the anterior abdominal wall, at the base of the umbilical cord.
it should not be seen after 12-13 weeks of gestation
it should never contain herniation of other organs, such as the liver
the extent of herniation is comparatively small (often <7 mm)
frequency: according to one study, this may be seen in 4
~65% of cases at 8 weeks
100% at 9-10 weeks
~25% at 11 weeks
For ultrasound imaging appearances, consider:
- 1. Roy G. Farquharson, Mary D. Stephenson. Early Pregnancy. (2010) ISBN: 9780521517089
- 2. Asim Kurjak, Sanja Kupesic. Color Doppler and 3D Ultrasound in Gynecology, Infertility and Obstetrics. (2003) ISBN: 9788180611025
- 3. David A. Nyberg. Diagnostic Imaging of Fetal Anomalies. (2003) ISBN: 9780781732116
- 4. Timor-Tritsch I, Warren W, Peisner D, Pirrone E. First-Trimester Midgut Herniation: A High-Frequency Transvaginal Sonographic Study. Am J Obstet Gynecol. 1989;161(3):831-3. doi:10.1016/0002-9378(89)90411-0
- 5. Bogers H, Baken L, Cohen-Overbeek T et al. Evaluation of First-Trimester Physiological Midgut Herniation Using Three-Dimensional Ultrasound. Fetal Diagn Ther. 2018;45(5):332-8. doi:10.1159/000489260