Module
20
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Abnormalities of the urachus

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
media/module20/t6q1_kystouraq.gif

  1. Bladder
  2. Urethra
  3. Urachus
    (fibrous relict of the allantois)
  4. Navel
  5. Umbilical cyst
  6. 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
media/module20/t6q2_fistborgne.gif

1
Bladder
2
Urethra
3
Urachus
(fibrous relict of the allantois)
4
Navel
7
Urine outflow onto the skin
8
External fistula
(urachal sinus)
9
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
media/module20/t6q3_fistouraq.gif

1
Bladder
2
Urethra
4
Navel
7
Outflow of the urine onto the skin
10
Uninterrupted urachal fistula