A 67-year-old man who has never had colonoscopy presented to the emergency room reporting abdominal pain, distention, constipation, and blood per rectum for the past 2 days. He says his bowel movements are thin in caliber. Computed tomography (CT) of abdomen and pelvis shows a large mass in the mid rectum with proximal colonic distention. Magnetic resonance imaging (MRI) of the pelvis with rectal cancer protocol shows a mid-rectal T4N2M0 lesion. The mass is not amendable to endoscopic placement of stent due to angulation. The best next step is