Septic arthritis of lumbosacral pseudoarthrosis

Case contributed by Chris O'Donnell
Diagnosis certain


Right back and loin pain with fever.

Patient Data

Age: 45 years
Gender: Male

Note: This case has been tagged as "legacy" as it no longer meets image preparation and/or other case publication guidelines.

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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