Sigmoid Volvulus Coffee-Bean Sign

An 82-year-old man with chronic constipation and Parkinson disease presents with three days of progressive abdominal distension, obstipation, and feculent vomiting. His caregiver reports two prior similar episodes that resolved with sigmoidoscopic decompression. On examination, the abdomen is markedly distended and tympanitic. Upright abdominal radiograph and CT imaging demonstrate the structure marked **A** — a massively dilated sigmoid loop measuring 12 cm in caliber with a classic coffee-bean configuration and a central fibrotic septum from apposed mesenteric edges. Which of the following is the MOST appropriate INITIAL management for this patient?