Additional information | Embryology | Anatomy

Box for secondary retroperitoneal organs: These organs were intraperitoneal during early development. Later on their mesenteries were pushed back against the posterior abdominal wall so that they became retroperitoneal. These organs are the pancreas, duodenum, ascending and descending colon.
Embryonic remnants

Embryonic Origin	Remnant
Foramen ovale	Fossa ovalis
Ductus arteriosus	Ligamentum arteriosum
Ductus venosus	Ligamentum venosum
Umbilical vein	Ligamentum teres hepatis
Umbilical arteries	MediaL umbilical ligament, part of internal iliac and superior vesical arteries.
Mesonephric or Wolffian ducts	In males it becomes efferent duct including the epididymis, vas deferens and seminal vesicles. In females, it remains as epoophoron and paroophoron, Gartner’s ducts.
Paramesonephric or Mullerian ducts	In females, it becomes the fallopian tubes, uterus, cervix, upper part of vagina. In males remnants seen in the prostatic utricle.
Urachus or allantoic stalk	MediaN umbilical ligament
Notochord	Nucleus pulposus

Meconium ileus: It is caused due to thick, desiccated meconium obstructing the ileum. It is seen in newborns with cystic fibrosis. Meconium ileus presents with bilious vomiting, abdominal distension with a high risk of perforation and peritonitis. Prenatal ultrasound shows hyperechoic masses from thick meconium, dilated bowel loops and non-visualization of the gallbladder. Imaging postnatally shows dilated bowel loops with or without (more common due to dry meconium) air-fluid levels, “soap bubble” or mottled appearance and in some cases, abdominal calcifications. Distal colon will show microcolon appearance due to disuse.