Breast Reconstruction with Rectus Abdominis ( 1 breast ) – (BIMC). A surgical process of rebuilding the shape and look of a breast, most commonly in women who have had surgery to treat breast cancer. Rectus abdominis, a muscle in your lower abdomen between your waist and your pubic bone. A flap of this skin, fat, and all or part of the underlying rectus abdominus muscle are used to reconstruct the breast.