Congenital anomalies
Urachus and Patent Urachus

Author: Alcides Chaux, M.D. (see Authors page)

Revised: 15 March 2016, last major update July 2011

Copyright: (c) 2003-2016,, Inc.

PubMed Search: Urachus, Patent urachus
Cite this page: Urachus and Patent Urachus. website. Accessed October 21st, 2016.
Definition / General

    Urachus - definition
  • Vestigial structure, 3-10 cm, located in a preperitoneal pyramid-shaped area formed by the bladder dome (base) and the obliterated umbilical arteries (tip of pyramid is towards umbilicus)
  • Pathology other than patent urachus is described separately in the Table of Contents

  • Arises from superior urogenital sinus
  • In fetus, connects bladder dome with allantois (embryonic diverticulum of hindgut, vessels are precursors to those in umbilical cord)
  • Fragmentation occurs post-partum when bladder descends into pelvis; urachus eventually becomes median umbilical ligament
Clinical Features
  • Urachal remnants may be found in midline or posterior bladder wall
  • Remnants seen at autopsy in 50% of fetuses, 33% of adults
  • Remnants are associated with urachal cysts, sinus, fistula, diverticulum, infections, adenocarcinoma of bladder; also urothelial carcinoma, villous adenoma, squamous cell carcinoma
Micro Description
  • Usually persists as fragmented tubules separated by fibrous cords, but without a desmoplastic tissue response
  • Composed of three layers: epithelium (stratified, columnar or urothelium), connective tissue and an outer smooth muscle layer (in continuity with detrusor muscle)
  • No goblet cells, no atypia in the epithelium
Micro Images

Dilated urachal remnant

Other images: #1; #2

Patent urachus - definition
  • Represents 50% of all urachal anomalies
  • Due to failure of obliteration of the urachal canal
  • Rare, because lumen typically closes at week 17 post-conception (Cells Tissues Organs 2010;191:422)
  • May appear later in life due to retubulization secondary to acquired obstructive bladder disease
  • Leads to urination through umbilicus
  • May be associated with infections (Staphylococcus aureus, Escherichia coli, Enterococcus, Citrobacter and, rarely Proteus species)

  • Also called persistent urachus
Case Reports
Diagrams / Tables

Images hosted on other servers:

Patent Urachus