The abnormalities of the urachus result from an incomplete closure of the allantois canal. One distinguishes 4 types of anomalies:
Urachal cyst: Such cyst is found somewhere along the allantois canal.
The cyst has a small connection to the bladder and can become infected, leading to its diagnosis.
Fig. 41 - Urachal cyst
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2
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Bladder
Urethra
Urachus
(fibrous relict of the allantois)
Navel
Umbilical cyst
Urachal cysts
Internal fistula: It is a diverticulum in the upper part of the bladder (urachal diverticulum)
External fistula: It is a blind terminating sac that emerges from the navel (urachal sinus)
Fig. 42 - Fistulas
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4
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9
Bladder
Urethra
Urachus
(fibrous relict of the allantois)
Navel
Urine outflow onto the skin
External fistula (urachal sinus)
Internal fistula (urachus diverticulum)
Urachal fistula: In a urachal fistula a lumen remains over the whole length of the urachus because the atrophy of the allantois fails to take place. The urine flows from the bladder directly through the navel onto the skin.
Fig. 43 - Urachal fistula
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Bladder
Urethra
Navel
Outflow of the urine onto the skin
Uninterrupted urachal fistula
