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Bladder

Congenital anomalies

Urachus and Patent Urachus


Reviewer: Alcides Chaux, M.D., Johns Hopkins University School of Medicine (see Reviewers page)
Revised: 3 July 2011, last major update April 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

See also Patent Urachus below

Urachus - definition
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● 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

Embryology
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● 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
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● 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
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● 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
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Dilated urachal remnant

Other images: #1; #2


Patent urachus

Patent urachus - definition
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● 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)

Terminology
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● Also called persistent urachus

Case reports
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● Giant umbilical cord edema caused by retrograde micturition through an open patent urachus (Pediatr Dev Pathol 2010;13:404)

Diagrams
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Patent Urachus

End of Bladder > Congenital anomalies > Urachus and Patent Urachus


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