Which procedure involves a surgical incision into the vaginal wall?

The procedure that involves a surgical incision into the vaginal wall is known as colpotomy. This technique is typically performed to access the pelvic cavity, often in gynecological surgeries. The colpotomy is done by making an incision in the vaginal wall to allow the surgeon to visualize or manipulate structures within the pelvis, such as the ovaries or the uterus, without needing to make an abdominal incision. This approach can be particularly advantageous in terms of recovery time and minimizing complications associated with larger incisions.

In contrast, the Manchester repair is a surgical procedure used to correct uterine prolapse and involves the cervix and ligaments rather than a direct incision through the vaginal wall for access purposes. The Ruby test is not a surgical procedure, but rather a diagnostic method to evaluate the functionality of the fallopian tubes. A purse-string suture is a technique used to close an opening or wound, but it does not specifically involve making an incision into the vaginal wall. Therefore, colpotomy is the correct choice for the procedure described in the question.