Occult infections causing persistent low-back pain.

Occult infections caused by indolent organisms may produce persistent back pain that may be difficult to diagnose. The usual findings considered indicative of spinal infection are not reliable in these cases. The authors describe nine patients who presented with occult infections of the lumbar spine. Two of the nine had no antecedent lumbar surgeries nor open wounds. The predominant organisms were diptheroids and coagulase-negative staphylococci. The diagnosis was established by the clinical course, pathologic tissue changes at surgery, cultures, and response to antibiotic therapy. Normal Westergren sedimentation rates were noted in seven of nine patients, and normal white blood cell counts in six of nine patients. With the exception of two positive computed tomography (CT) scans, one positive gallium scan, and one positive magnetic resonance imaging (MRI) scan, all remaining imaging studies were negative for infection. In many cases, the infection neither was limited to nor involved the disc space.