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 t he case notes of all patients attending Royal Bournemouth and Poole Hospita ls with probable septic discitis on magnetic resonance imaging (MRI). Twent y-two cases of septic discitis were identified, suggesting an annual incide nce 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 erythroc yte sedimentation rate (ESR) in 91%. Diagnosis was originally by MRI in 86% of patients, with plain radiographs not diagnostic of discitis in the earl y stages of the infection. Staphylococcus aureus was the commonest pathogen (41%), but in 18% of patients, no organism was identified. The major predi sposing factors to septic discitis were invasive procedures (41%), underlyi ng cancer (25%) and diabetes (18%). Pre-existing degenerative spinal diseas e was found in 50% of patients. Four patients whose causative organism was not isolated had a poorer outcome: one death and three with increased morbi dity. 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 consid ered in any patient who has severe localized pain at any spinal level, espe cially if accompanied by fever and elevated ESR, or in the immunosuppressed .