Migration of a bladder diverticulum stone into the rectum revealing an advanced rectal process.

Rectovesical fistulas are rare and typically result from inflammatory or neoplastic conditions in the small pelvis. They occur within a pelvic region that has been altered by local inflammatory or neoplastic processes. This explains the challenges in detecting these fistulas using conventional imaging techniques, despite the effectiveness of CT and MRI. Colonic diverticulosis is the primary cause of colovesical fistulas. To date, there have been no reported cases of a rectovesical fistula associated with a bladder diverticulum in the literature. We present a case of a patient who presented with a large stone within a bladder diverticulum. The migration of this stone into the rectum revealed an advanced rectal tumor. The unique aspect of our case is primarily the presence of a rectovesical fistula arising from a lateral bladder diverticulum. Additionally, we observed the migration of the diverticular calculus from the bladder to the rectum.