Quiz: What’s causing this acute abdominal pain?

Just so you know, this is a tricky one!
abdominal pain

A 71-year-old male with a history of cough, atrial fibrillation and hypertension presents to the emergency department with a one-day history of severe abdominal pain.

On examination, his vital signs are stable. Laboratory findings reveal an expected INR of 2.8, but are otherwise unremarkable.