The evolution of surgical robotics is following the progress of developments in Minimally Invasive Surgery (MIS), which is moving towards Single-Incision Laparoscopic Surgery (SILS) procedures. The complexity of these techniques has favored the introduction of robotic surgical systems. New bimanual robots, which are completely inserted into the patient's body, have been proposed in order to enhance the surgical gesture in SILS procedures. However, the limited laparoscopic view and the focus on the end-effectors, together with the use of complex robotic devices inside the patient's abdomen, may lead to unexpected collisions, e.g., between the surrounding anatomical organs not involved in the intervention and the surgical robot. This paper describes a computer guidance system, based on patient-specific data, designed to provide intraoperative navigation and assistance in SILS robotic interventions. The navigator has been tested in simulations of some of the surgical tasks involved in a cholecystectomy, using a synthetic anthropomorphic mannequin. The results demonstrate the usability and efficacy of the navigation system, underlining the importance of avoiding unwanted collisions between the robot arms and critical organs. The proposed computer guidance software is able to integrate any bimanual surgical robot design.