All the metaphors apply—knife in the gut, bullet in the belly, skewer in the stomach—except this attack is from within.
The condition: Take your pick. Since the area between your ribs and your hips is jam-packed with organs, the pain can be a symptom of either appendicitis, pancreatitis, or an inflamed gallbladder.
In all three cases, the cause is the same: Something has blocked up the organ in question, resulting in a potentially fatal infection. Exploding organs can kill a guy. See a doctor before this happens.
The diagnostics: If the pain is in your lower-right abdomen and your white-blood-cell count is up, says Dr. Kra, it's probably appendicitis (out comes the appendix).
Pain in your upper abdomen with high white blood cells usually spells an inflamed gallbladder.
And if it hurts below your breastbone and certain enzymes in the blood are elevated, then pancreatitis is probably the culprit. (The pancreas stays, but a gallstone may be blocking things up. If so, the stone and the gallbladder may have to come out.)