A lower anterior resection, formally known as anterior resection of the rectum and anterior excision of the rectum or simply anterior resection (less precise), is a common surgery for rectal cancer and occasionally is performed to remove a diseased or ruptured portion of the intestine in cases of diverticulitis. It is commonly abbreviated as LAR. LARs are for cancer in the proximal (upper) two-thirds of the rectum which lends itself well to resection while leaving the rectal sphincter intact.