A lumbosacral transitional vertebra is present in about one in ten Australian patients with lumbar radiographs, and the reporting radiologist identified fewer than a third of them. On lumbar MRI without a whole-spine localiser, more than a third of transitional vertebrae are read as normal segmentation, and among those that are recognised the numbering is wrong in more than half. Most wrong-level spine surgery occurs in patients with variant anatomy of this kind.

This guide is for radiologists and radiology registrars reporting lumbar spine radiographs, CT and MRI, and for those performing image-guided spinal injections. It covers the identification and classification of a transitional vertebra (Castellvi and Jenkins, with the measurements to record on CT), vertebral enumeration and the methods with published support, the findings on each modality that bear on whether the segment is symptomatic, the associated findings at the level above, a report structure with a checklist, the diagnostic injection and its Medicare items, and the pitfalls that recur in the literature. A closing chapter sets out what patients report about their imaging and their reports.

Every clinical figure is drawn from the published evidence and referenced. Notes on verification state what could and could not be checked against the primary sources.