Urachus

The urachus is a fetal structure that originates from the allantois and connects the fetal bladder to the umbilicus. After birth, the urachus normally becomes the median umbilical ligament. However, incomplete obliteration of the urachus can lead to various anomalies, some of which may increase the risk of infection or malignancy.

Embryological Development

Formation: The allantois forms from the hindgut and extends into the urogenital sinus.
Transformation: The allantois becomes the urachus, a duct that connects the fetal bladder to the umbilicus.
Postnatal Fate: Normally, the urachus obliterates and becomes the median umbilical ligament, covered by the median umbilical fold of the peritoneum.

Urachal Anomalies

The failure of the urachus to completely involute can lead to the following conditions:

Anomaly	Description	Clinical Presentation
Patent Urachus	Total failure of the urachus to obliterate.	Urine discharge from the umbilicus.
Urachal Cyst	Partial failure of the urachus to obliterate, forming a fluid-filled cavity lined with uroepithelium.	Painful mass below the umbilicus that can become infected.
Vesicourachal Diverticulum	Slight failure of the urachus to obliterate, resulting in an outpouching of the bladder.	Usually asymptomatic; may present with symptoms if infected.

Comparison with Related Anomalies

Condition	Anomaly Description	Clinical Feature
Patent Urachus	Failure of urachus to obliterate	Urine discharge from the umbilicus
Urachal Cyst	Cyst formation due to partial obliteration	Painful mass below the umbilicus
Vesicourachal Diverticulum	Bladder outpouching due to incomplete obliteration	May be asymptomatic
Normal Vitelline Fistula	Complete failure of vitelline duct to close	Fecal discharge from umbilicus
Meckel Diverticulum	Partial failure of vitelline duct obliteration	Asymptomatic or painless rectal bleeding

Points to Remember

Anomalies Risk: Urachal anomalies, if untreated, can lead to infections and increase the risk of malignancies like adenocarcinoma.
Median Umbilical Ligament: The obliterated urachus is represented by the median umbilical ligament after birth.
Clinical Significance: Recognizing symptoms of urachal anomalies is crucial in pediatric diagnosis to prevent complications.

Key Takeaways

Obliterated Urachus: Should result in a median umbilical ligament.
Patent Urachus: Presents with urine discharge from the umbilicus.
Urachal Cyst: Can manifest as a painful, sometimes infected, mass.
Vesicourachal Diverticulum: Generally asymptomatic but may have complications if infected.

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