A case ascertainment study of septic discitis: clinical, microbiological and radiological features

We studied the spectrum of septic discitis presenting to two busy district general hospitals over 2.5 years (November 1996 to April 1999), surveying the case notes of all patients attending Royal Bournemouth and Poole Hospitals with probable septic discitis on magnetic resonance imaging (MRI). Twenty-two cases of septic discitis were identified, suggesting an annual incidence of 2/100 000/year. Seventy-three percent of patients were aged greater than or equal to 65 years. In 91% of patients, back pain was the presenting symptom, with neurological signs evident in 45% of patients. Fever > 37.5 degreesC was present in 68% of patients, and a marked elevation of erythrocyte sedimentation rate (ESR) in 91%. Diagnosis was originally by MRI in 86% of patients, with plain radiographs not diagnostic of discitis in the early stages of the infection. Staphylococcus aureus was the commonest pathogen (41%), but in 18% of patients, no organism was identified. The major predisposing factors to septic discitis were invasive procedures (41%), underlying cancer (25%) and diabetes (18%). Pre-existing degenerative spinal disease was found in 50% of patients. Four patients whose causative organism was not isolated had a poorer outcome: one death and three with increased morbidity. Our estimated incidence rate (2/100 000/year) is higher than that in previous studies and may be due to a higher detection rate with MRI and/or a genuine increase in the number of cases. Septic discitis should be considered in any patient who has severe localized pain at any spinal level, especially if accompanied by fever and elevated ESR, or in the immunosuppressed.