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Pathology for Urologists

Urachal Remnant


Image A
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Image B
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  • Urachus is a vestigial tubular structure that connects the urinary bladder to the allantois during early embryonic development.
  • Typically arises from the bladder apex and continues upward within the space of Retzius on a varied course toward the umbilicus.
  • When complete, urachal remnants consist of an epithelial canal surrounded by connective tissue and musculature (image A), (image B), (image C), & (image D).
  • With full regression, the completely obliterated fibrous remnant becomes the median umbilical ligament.
  • Urachal remnant can be seen incidentally in up to 32% of adult bladder autopsies or cystectomies.

Image C
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Image D
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  • In <20 years old are mostly lined by urothelial cells (95%), and with higher proportion of columnar cells with or without Goblet cells (30%) in older adults.
  • Structural anomalies may arise along the urachus during regression:
    • Patent urachus: completely open urachal lumina from umbilicus to bladder.
    • Urachal cyst: no connection to bladder lumen or umbilicus; most common anomaly (36%).
    • Urachal sinus: pouch opens to umbilicus.
    • Vesicourachal diverticulum: pouch opens to bladder lumen.
  • Cancers can arise from any of the urachal remnant compartments, but the vast majority originates from the canal epithelium (carcinoma) in adults.
  • Urachal carcinomas are predominantly adenocarcinoma believed to evolve from remnant epithelium intestinal metaplasia.

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