Placenta
Nonneoplastic placental conditions and abnormalities
Embryonic remnants
Embryonic remnants
Last author update: 1 August 2015
Last staff update: 29 October 2020
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PubMed Search: Embryonic remnants placenta
Table of Contents
Definition / general | Terminology | Epidemiology | Pathophysiology / etiology | Diagrams / tables | Clinical features | Case reports | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) imagesCite this page: Kowalski PJ, Ziadie MS. Embryonic remnants. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentaembryonicremn.html. Accessed January 8th, 2025.
Definition / general
- Vestigial structures representing extraembryonic ductal connections (the allantoic duct and the omphalomesenteric duct) in the primitive connecting (umbilical) stalk can be commonly seen in term placentas
Terminology
- Yolk sac is an early embryonic structure, a portion of which will eventually be incorporated into the gut of the embryo; vitelline vessels supply the yolk sac and constitute the vitelline circulation
- Allantois is the primitive extraembryonic urinary bladder and will eventually become the urachus, which connects the fetal bladder to the yolk sac; the allantoic duct originates as an outpouching of the yolk sac
- Omphalomesenteric (vitelline) duct connects the midgut lumen with the yolk sac in the developing fetus
- See diagram below
Epidemiology
- Allantoic duct remnant is present in the proximal portion of 15% of umbilical cords
- Omphalomesenteric duct remnant is present in about 1.5% of umbilical cords, often associated with remnants of vitelline vessels, seen in about 7% of umbilical cords
Pathophysiology / etiology
- Allantoic duct usually regresses and is completely obliterated by 15 weeks gestation
- Its persistence in the umbilical cord is common
- Remnant (of the allantoic duct) between the umbilicus and the fetal urinary bladder persists as the medial umbilical ligament
- Omphalomesenteric duct usually obliterates between 9 - 16 weeks gestation following gut rotation but can alternatively persist in term placentas
Diagrams / tables
Images hosted on other servers:
Clinical features
- For allantoic duct remnants, usually no clinical significance
- Rare cases of patent duct remnants can show urinary leakage from a clamped umbilical stump or cysts that may persist into adulthood
- For omphalomesenteric duct remnants, usually no clinical significance
- Rare cases of patent duct remnants can be symptomatic if direct communication is maintained with the fetal bowel or if ectopic gastric, pancreatic or intestinal mucosa stimulates tissue responses
- Omphalomesenteric duct remnants have also been associated with intestinal atresia, Meckel diverticulum or intestinal protrusion into the umbilical cord through the duct
Case reports
- Newborn with esophageal atresia, small omphalocele and ileal prolapse (J Pediatr Surg 2013;48:E9)
- Infant with abscess of allantoic duct remnant (Am J Obstet Gynecol 1989;161:334)
- 24 year old man with symptomatic omphalomesenteric cyst (J Gastrointest Surg 2013;17:1503)
- Umbilical cord cysts of allantoic and omphalomesenteric remnants with progressive umbilical cord edema (Fetal Diagn Ther 2009;25:250)
Gross description
- Typically no gross findings are evident (unless a rare cyst is present)
- Yolk sac remnant: flat, gold nodule between the amnion and chorion of fetal surface or membranes
Gross images
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Yolk sac remmant
Microscopic (histologic) description
- Allantoic duct remnants are usually located between the umbilical arteries of the proximal portion of the umbilical cord and are rarely accompanied by smooth muscle
- Epithelium of the duct is cuboidal to flat and generally is of transitional type although mucin producing epithelium can be found
- Small vessels around the periphery of the duct remnant may be occasionally seen
- Omphalomesenteric duct remnants are also more common in the proximal umbilical cord but are present at the cord periphery and often have a smooth muscle wall
- Epithelium of the duct is cuboidal to columnar with an intestinal phenotype
- Rarely, mucosa resembling liver, pancreas, stomach or small intestine can be seen
- Frequently, paired or clustered vitelline vessels (without muscular walls) will be associated with duct remnants
Microscopic (histologic) images
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Allantoic duct remnant
Omphalomesenteric duct remnant
