What is the proposed mechanism for the association of imperforate anus and rectovesical fistula in males?

The association of an imperforate anus and rectovesical fistula in males is primarily attributed to the failure of the urorectal septum. During embryonic development, the urorectal septum forms to separate the cloaca into the rectum and the urogenital sinus. If the urorectal septum does not develop properly, it can lead to malformations, including an imperforate anus and an abnormal connection between the rectum and the bladder (rectovesical fistula).

In this context, if the urorectal septum fails to divide the cloaca adequately, the result can be both the absence of a patent anal opening (imperforate anus) and the formation of a fistula between the rectum and the bladder, which can lead to complications such as urinary tract infections and issues with bowel function. This mechanism highlights the importance of proper embryological development in the formation of the anatomic structures involved.