MRCP2-1965

MRCP2-1965

An 80-year-old man presents to the Emergency department with intermittent abdominal pain, nausea, vomiting, and constipation. He has also experienced a 2-stone weight loss and decreased appetite over the past three months. His medical history includes an anterior resection for colonic cancer three years ago, complicated by an abscess and wound infection. On examination, he appears pale and thin with a distended abdomen. Laboratory investigations reveal a low hemoglobin level, low MCV, and normal electrolyte levels. Arterial blood gas analysis shows a slightly low PCO2 and normal PO2. What is the most likely cause of his symptoms?