MG are difficult to diagnose and share a common natural history with single gallbladders, without evidence of increased risk for malignancy. Excision of both gallbladders is indicated in symptomatic stone disease. However, prophylactic cholecystectomy must be considered for type 2 MG, since it cannot be preoperatively differentiated from a Todani II bile duct cyst, which is associated with a risk of malignant transformation.