List the differential diagnosis of low back pain.
Low back pain can be caused by a multitude of disease processes. The most common cause is muscular in origin, often presenting as myofascial syndrome, with trigger points noted on physical examination. Common skeletal causes include degenerative disease of the vertebral column (osteoarthritis), disc disease (herniated nucleus pulposus), and joint involvement (facet syndrome and sacroiliitis). Rheumatoid and other types of inflammatory arthritis can also cause low back pain. Less frequent skeletal causes include metabolic (osteoporosis), neoplastic, infectious (osteomyelitis), traumatic (fractures), or congenital (scol-iosis). Back pain of neurologic origin may originate from irritation of nerves by herniated discs, osteophytes, tumors, or disease of the neuraxis such as inflammation (herpes zoster) or neoplasms (intradural or epidural tumors). Low back pain may also be referred from intra-abdominal/ thoracic diseases such as aortic aneurysms, pancreatic cancer/inflammation, lower lobe pneumonias, sarcomas, lymphomas, or visceral processes involving the genito-urinary or gastrointestinal tracts. Because of the large dif-ferential diagnosis, a thorough investigation and evaluation is necessary to determine the cause of the lower back pain.