A 63-year-old man underwent endoscopic evaluation of the rectal stump for rectal bleeding and suffered a massive cerebral air embolism with severe neurological impairment and subsequent death. The patient underwent a Hartmann's procedure 9 month previously for ischaemic bowel and was noted to have portal hypertension at laparotomy. We hypothesise that air entered the venous plexus around rectum and entered the azygos vein via a porto-systemic shunt and travelled retrogradely via the superior vena cava to the venous sinuses of the brain.