Sometimes back pain can be the result of a problem not located in the back. Possible causes include:
• Kidney stones or kidney infections. Because of the kidneys' location in the lower back, problems with the kidney may be felt as back pain.
• Pregnancy. Weight gain from pregnancy can both stress the back and stretch and weaken muscles that support the spine.
• Obesity. Being overweight or obese, particularly if excess weight is carried in the abdomen, places stress on back muscles, causing pain.
• Endometriosis. This is a condition in which the endometrial tissue (tissue that lines the uterus) migrates from the uterus and deposits on other organs and structures. Pain from endometriosis is often felt in the abdomen and back.
• Aortic aneurysms. In rare cases, the aorta (the body's main artery that originates at the heart and runs down the body just in front of the spine) develops an aneurysm, a balloon-like swelling in the artery's muscular wall. If the wall ruptures or causes compression of the blood vessels that run off it, the result can be pain that is felt in the chest, abdomen and/or lower back. This is a medical emergency, requiring immediate treatment.
• Tumors. In rare cases, tumors – either malignant (cancerous) or benign (not cancerous) – can affect the tissues of or near the spine, causing pain.