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.

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).

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.