Rectal cancer at the peritoneal reflection. Preoperative MRI accuracy and histophatologic correlation. Prospective study Eduardo Álvarez Sarrado; Francisco Giner Segura; Adela Batista Domenech; Álvaro Garcia-Granero García-Fuster; Matteo Frasson; Polina Rudenko; Blas Flor Lorente; Eduardo Garcia-Granero Ximénez;