An aneurysm occurs when part of an artery wall weakens, allowing it to widen abnormally or balloon out. According to the American Heart Association, these bulges can occur anywhere, but aortic aneurysms refer to those that develop along the aorta. At about a foot long and an inch in diameter, the aorta is the largest vessel in the body, and it extends from the heart through the chest to the abdomen. Most aortic aneurysms occur in the abdomen, though the chest is also possible. In either case, if an aortic aneurysm bursts it often causes back pain that radiates into the abdomen. “It's severe and comes on suddenly,” says Moore. A ruptured aortic aneurysm is a medical emergency, because it can lead to life-threatening internal bleeding. Aortic aneurysms are most common among men over age 60 who smoke or have high cholesterol. But anyone who has extreme pain in the belly or back that doesn't go away should seek immediate medical attention.
Fewer than half of people with appendicitis, an inflammation of the appendix, have the traditional symptoms of nausea, vomiting, and sharp pain in the lower right abdomen. While you might simply have pain elsewhere in your midsection, you might develop lower back pain. The reason: Although the appendix usually resides in their lower right abdomen, about 15% of people have their appendix in their back near a kidney, thanks to an anatomical quirk. So when this mysterious organ gets inflamed or ruptures, they may complain of lower back pain instead of stomach pain. “While all doctors should have learned about this in medical school, it’s not usually the first thing we think about when someone comes in with back pain,” says Moore. Anytime you suspect you have appendicitis, seek medical attention quickly: An infected appendix can rupture less than 24 hours after symptoms begin, and if infection sets in it can lead to shock. You'll likely need surgery, and delaying it can lead to complications including repeated operations and a longer recovery.
There’s a host of below-the-belt reasons that women might experience back pain. For instance, 25% have a “retroverted uterus,” which is when your uterus tilts backward. “When many of these women have menstrual cramps, they’ll feel it as pain in the lower back instead of pain in the lower abdomen,” says Moore. Rarely, fibroids can also cause back pain if they press against the muscles and nerves of the lower back, but having a tilted uterus makes that more likely. (This is what it feels like to live with fibroids, according to 10 women who have them.) Lower back pain can also be a symptom of endometriosis, which occurs when bits of the tissue that lines the uterus grows on other pelvic organs.