An 80-year-old patient presents with abdominal distension, vomiting, and absolute constipation. X-ray shows a "coffee bean sign." What is the most likely diagnosis?

Explanation

The "coffee bean sign" on abdominal X-ray is pathognomonic of sigmoid volvulus. It appears as a large, dilated loop of sigmoid colon arising from the pelvis. Initial management is attempted endoscopic decompression.