Septic arthritis of lumbosacral pseudoarthrosis

Case contributed by Dr Chris O'Donnell

Presentation

Right back and loin pain with fever

Patient Data

Age: 45
Gender: Male

Clinicians thought that symptoms were due to obstructed, infected kidney thus ordered CT KUB

Based on CT findings, MRI with IV gadolinium was ordered

Segmentation anomaly whereby an enlarged right transverse process of L5 articulates with the ala of the sacrum producing a pseudoarthritis. This now shows the typical features of septic arthritis with bone erosion and soft tissue swelling as well as diffuse enhancement but no abscess. Inflammation extends into the iliacus and piriformis muscles as well as the right sacro-iliac joint.

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