Placenta
Umbilical cord
Embryonic remnants

Reviewer: Paul J. Kowalski, M.D. (see Reviewers page)

Revised: 26 August 2015, last major update August 2015

Copyright: (c) 2002-2015, PathologyOutlines.com, Inc.

PubMed Search: Embryonic remnants [title]
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
  • The 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
  • The 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
  • The omphalomesenteric (vitelline) duct connects the midgut lumen with the yolk sac in the developing fetus

  • Epidemiology
  • An allantoic duct remnant is present in the proximal portion of 15% of umbilical cords
  • An 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
  • The allantoic duct usually regresses and is completely obliterated by 15 weeks gestation
    • Its persistence in the umbilical cord is common
    • A remnant (of the allantoic duct) between the umbilicus and the fetal urinary bladder persists as the medial umbilical ligament
  • The omphalomesenteric duct usually obliterates between 9-16 weeks gestation following gut rotation, but can alternatively persist in term placentas
  • 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)
  • Micro 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
    • The 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
    • The 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
  • Micro Images
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    Allantoic duct remnant

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    Omphalomesenteric duct remnant