Pyogenic arthritis of a lumbar facet joint, a rare cause of retroperitoneal abscess: a case report

INTRODUCTION: Pyogenic arthritis in the spinal facet joint is rare, although the wide availability of magnetic resonance imaging (MRI) has increased the detection rate. Pyogenic arthritis of a lumbar facet joint is often combined with abscesses in the paraspinal muscles and epidural space. However, there is no report of pyogenic arthritis of a lumbar facet joint causing a retroperitoneal abscess. We report on a patient with pyogenic lumbar facet arthritis, which caused a huge retroperitoneal abscess. CASE REPORT: The patient was a 67-year-old woman with a 3-week history of fever and pain in her lower back, left lower abdomen, and left thigh. Blood tests revealed high levels of inflammatory markers. Computed tomography (CT) showed a huge retroperitoneal abscess, and MRI of the lumbosacral spine showed an abscess at the left L5/S facet joint, that had invaded into the paraspinal muscles, epidural space, and retroperitoneal space. We diagnosed pyogenic arthritis of a lumbar facet joint combined with abscesses in the paraspinal muscles, epidural space, and retroperitoneal space. CT-guided percutaneous drainage of the retroperitoneal abscess was performed, and the patient was treated with antibiotics. The bacterial strain cultured was Streptococcus pneumoniae. The patient recovered after 10 weeks of antibiotic treatment combined with additional CT-guided percutaneous drainage. CONCLUSIONS: Pyogenic arthritis of a lumbar facet joint can cause a retroperitoneal abscess through the vertebral foramen as well as the more common abscesses in the paravertebral muscles and epidural space, and the finding of MRI is characteristic. The clinician should suspect of pyogenic arthritis of a lumbar facet joint in a patient presenting with retroperitoneal abscesses that are not secondary to diseases of kidney or gastrointestinal tract.