PET-CT confirms the diagnosis of pyogenic spondylodiscitis complicated by psoas abscess.

To cite: Davison JM, Graham JA, Nieves NM, et al. BMJ Case Reports Published online: [please include Day Month Year] doi:10.1136/bcr-2012008264 DESCRIPTION The authors report a case of a 64-year-old woman with a history of diabetes mellitus (DM) and haemodialysis dependent end-stage renal disease admitted to the intensive care unit for hypoglycaemia, hyperkalaemia, elevated white blood cell count and elevated inflammatory markers. During the course of her hospitalisation, she complained of persistent low back pain. Although gadolinium contrast agents are generally contraindicated in these patients due to significant risk of nephrogenic systemic fibrosis, lumbar spine MRI with gadopentetate dimeglumine contrast was felt to be absolutely necessary, given the need to confirm spondylodiscitis in order to guide treatment. We adhered to strict departmental protocol with written consent and haemodialysis within hours after the examination. Results showed enhancement of the right L5 pedicle and moderate degenerative disc disease. The findings of right pedicle enhancement were interpreted as non-specific, representing infection or neoplasm. Several days later, an F-18 fluorodeoxyglucose positron emission tomographycomputerised tomography (PET-CT) exam identified spondylodiscitis with a right psoas abscess (figures 1–3), a diagnosis confirmed by methicillin resistant Staphylococcus aureus (MRSA) bacteraemia. Fortunately, in the year since the MRI, the patient has not reported clinical findings to be consistent with nephrogenic systemic fibrosis. Pyogenic spondylodiscitis is the major manifestation of haematogenous osteomyelitis in patients over the age of 50, preferentially affecting the lumbar spine. S aureus is the major infective agent, responsible for greater than 50% of cases. DM is the most common risk factor. The adult intervertebral disc typically is avascular, therefore the marrow in the region of the vertebral body end plate is usually infected first, with subsequent spread to the disc. MRI is the imaging modality of choice with an accuracy of 94%. Early MRI findings typically include low signal intensity on T1-weighted images in endplate of the affected vertebral body along with contrast enhancement. Further progression usually involves the disc, manifested as high T2 signal. Pyogenic spinal osteomyelitis rarely involves the posterior elements of the vertebrae. Paraspinal abscess is a known uncommon complication, usually seen in advanced cases.