Sudden or severe abdominal pain: Centralized around the belly button. Sharp and unexpected.
What it might be: An aortic aneurysm or rupture, which is a bulge in the aorta, the largest artery in the body. Alternatively, it could be a perforation of the viscus (stomach, intestine or other hollow organ), usually due to an ulcer. Or intestinal ischemia, which means blood flow slows or stops to the intestines, causing oxygen starvation in affected tissues. Other possibilities include gallstones, diverticulitis (inflammation in the large intestine), irritable bowel syndrome or appendicitis.