If the uro-rectal septum does not migrate propoerly and in the correct plane. A multitude of anomalies can result. For example, if the urorectal septum does not reach teh cloacal membrane, there will be no anus. This will lead to a fistula forming from the rectum to an adjacent structure. This structure can be the urethra, leading to a recto-urethral fistula; the bladder, leading to a recto-vesical fistula or even the vagina, leading to a recto-vaginal fistula.