Bladder & urothelial tract

Congenital anomalies

Urachus



Last author update: 11 December 2023
Last staff update: 11 December 2023

Copyright: 2003-2024, PathologyOutlines.com, Inc.

PubMed Search: Urachus, benign nonneoplastic lesions

Bohdan Zoshchuk, M.D.
Y. Albert Yeh, M.D., Ph.D.
Page views in 2023: 14,918
Page views in 2024 to date: 5,215
Cite this page: Zoshchuk B, Morisetti M, Beeter MC, Yeh YA. Urachus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bladderurachus.html. Accessed April 14th, 2024.
Definition / general
  • The urachus, originated from remnants of allantois, is a fibrous cord connecting the umbilicus to the anterosuperior aspect of the bladder dome; usually obliterates at birth and becomes the median umbilical ligament (Kumar: Robbins & Cotran Pathologic Basis of Disease, 10th Edition, 2020)
  • Urachal pathology results from failure of involution of the embryonic structures, resulting in the formation of a urachal cyst, umbilical urachal sinus, vesicourachal diverticulum or patent urachus (completely patent, tubular remnant communicating the developing bladder and the umbilical cord) (StatPearls: Patent Urachus [Accessed 29 December 2022])
Essential features
Terminology
  • Patent urachus: completely patent tubular lesion communicating the bladder and the umbilical cord
  • Umbilical urachal sinus: tubulocystic lesion with an opening in the umbilicus while the other end is closed (BMJ Case Rep 2016;2016:bcr2016215374)
  • Vesicourachal diverticulum: tubulocystic lesion with an opening in the bladder while the other end is closed
  • Urachal cyst: cystic structure with both the umbilical and bladder ends closed (BMJ Case Rep 2016;2016:bcr2016215374)
  • Urachal remnants within bladder wall: tubulocystic lesion located in the bladder wall
ICD coding
  • ICD-10: Q64.4 - malformation of urachus
    • Urachus, congenital
    • Patent urachus
    • Patent (congenital) urachus
  • ICD-11: LB03.0 - allantoic duct remnants or cysts
Epidemiology
Sites
Pathophysiology
Etiology
Diagrams / tables

Images hosted on other servers:
Classification of urachal anomalies

Classification of urachal anomalies

Urachal cysts and fistulas

Urachal cysts and fistulas

Clinical features
Diagnosis
  • Prenatal:
    • Ultrasonography (US): increased thickness of the umbilicus observed as an extra-abdominal cystic mass (Medicina (Kaunas) 2022;58:1621)
    • Early prenatal detection for appropriate counseling for postpartum corrective surgery
  • Postnatal:
  • Ultrasound: diagnostic for 82% of cysts, 100% of sinuses, 100% of patent urachus
  • Voiding cystourethrogram: diagnostic for 100% of patent urachus
  • CT scan: diagnostic for 71% of cysts (J Pediatr Urol 2007;3:500)
Laboratory
  • Check creatinine level if urine in the umbilical drainage is suspected (StatPearls: Patent Urachus [Accessed 10 January 2023])
  • Microorganisms cultured from the umbilical drainage often include Staphylococcus aureus, Escherichia coli, Enterococcus, Citrobacter and rarely, Proteus species
Radiology description
Radiology images

Contributed by Bohdan Zoshchuk, M.D.
Patent urachus, US Patent urachus, US

Patent urachus, ultrasound



Images hosted on other servers:
Hypoechoic mass

Hypoechoic mass

Patent urachus, fistulography

Patent urachus, fistulography

Patent urachus, CT scan

Patent urachus, CT scan

Cyst protruding through umbilicus

Cyst protruding through umbilicus

Prognostic factors
Case reports
Treatment
Clinical images

Images hosted on other servers:
Persistent urachus

Persistent urachus

Before and after surgery

Before and after surgery

Urachal cysts - sinus tract between bladder dome and umbilicus

Urachal cysts - sinus tract between bladder dome and umbilicus

Infected urachal cyst

Infected urachal cyst

Urachal cyst attached to Meckel diverticulum

Urachal cyst attached to Meckel diverticulum

Gross description
Gross images

Images hosted on other servers:
Patent urachus, autopsy specimen

Patent urachus, autopsy specimen

Benign urachal lesion

Benign urachal lesion

Infected urachal cyst and fibrous tract

Infected urachal cyst and fibrous tract

Urachal cyst containing stones

Urachal cyst containing stones

Urachal sigmoid fistula

Urachal sigmoid fistula

Inflamed urachal cyst

Inflamed urachal cyst

Microscopic (histologic) description
  • Patent urachus, umbilical urachal sinus, vesicourachal diverticulum
    • Completely or incompletely opened structures lined by benign urothelium with or without squamous metaplasia
    • Glandular metaplasia may present
  • Urachal cyst
    • Cystic remnants lined by benign cuboidal cells, flattened epithelial cells or urothelial cells
    • Intestinal (columnar cells with or without goblet cells) metaplasia may present
  • Urachal remnants in bladder wall (Cheng: Urologic Surgical Pathology, 4th Edition, 2019)
    • Embryonic remnants in the bladder wall that are lined by benign urothelial cells
    • Squamous or glandular (columnar cells with or without goblet cells) metaplasia may present
Microscopic (histologic) images

Contributed by Bohdan Zoshchuk, M.D. and Manasa Morisetti, M.D.
Patent urachus Patent urachus Patent urachus

Patent urachus

Urachal remnant

Urachal remnant in bladder wall


Urachal remnant Urachal remnant

Urachal remnant in bladder wall

Urachal sinus Urachal sinus

Umbilical urachal sinus

Molecular / cytogenetics description
Sample pathology report
  • Urinary bladder wall lesion, excision:
    • Tubulocystic lesion lined by urothelial epithelium consistent with urachal remnants (see comment)
    • Comment: Sections of the bladder wall lesion show a tubular structure lined by urothelium and attached to the muscularis propria. These findings are consistent with urachal remnants.
Differential diagnosis
Board review style question #1
During bladder catheterization in a newborn boy, the tip of the catheter came out through his enlarged umbilical stump. What is the diagnosis?

  1. Patent omphalomesenteric duct
  2. Patent urachus
  3. Umbilical urachal sinus
  4. Urachal cyst
  5. Vesicourachal diverticulum
Board review style answer #1
B. Patent urachus. Patent urachus creates a tubular connection between the umbilicus and the anterosuperior wall of the bladder. Answer A is incorrect because patent omphalomesenteric duct has connection between umbilicus and small intestine. Answers C, D and E are incorrect because umbilical urachal sinus, urachal cyst and vesicourachal diverticulum cannot be probed through.

Comment Here

Reference: Urachus and patent urachus
Board review style question #2

A 50 year old man complained of abdominal pain for several weeks. A noncontrast CT scan of the abdomen was performed. There was a cystic lesion in the anterosuperior bladder wall. No connection between the bladder and the umbilicus was noted. Surgical excision followed by pathological examination was performed. The photomicrograph is shown above. What is the diagnosis?

  1. Mesonephric remnant
  2. Omphalomesenteric duct remnant
  3. Urachal remnant in bladder wall
  4. Vitelline duct remnant
Board review style answer #2
C. Urachal remnant in bladder wall. Urachal remnants within the bladder wall are usually lined by urothelium but can show metaplastic changes, such as squamous metaplasia seen here. Mesonephric remnants are composed of small tubules lined by low columnar to cuboidal epithelial cells. The cells are immunoreactive to CK903, CD10 and vimentin. Omphalomesenteric duct remnant is the same as vitelline duct remnant, which is lined by gastrointestinal epithelium.

Comment Here

Reference: Urachus and patent urachus
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