Paravertebral Abscess¶
Definition¶
A paravertebral abscess is a collection of purulent material in the paraspinal soft tissues, typically arising from contiguous spread of spondylodiscitis or vertebral osteomyelitis. It can also develop from direct inoculation (post-surgical, penetrating trauma) or hematogenous seeding. In the thoracolumbar spine, paravertebral abscesses may track along the psoas muscle, forming a psoas abscess.
Imaging Findings¶
MRI¶
- Location — Paraspinal soft tissues adjacent to the infected vertebral segment. In the lumbar spine, may extend into and along the psoas muscle bilaterally.
- T1-weighted — Iso- to hypointense collection in the paravertebral space
- T2-weighted — Hyperintense collection
- Post-contrast — Rim enhancement of the abscess wall with non-enhancing central pus. Surrounding soft tissue edema and enhancement.
- DWI — Restricted diffusion within the abscess
- Associated spondylodiscitis — Almost always present in pyogenic infections
CT¶
- Rim-enhancing hypodense paravertebral collection
- May contain gas (strongly suggests pyogenic infection)
- CT is excellent for guiding percutaneous drainage
- Calcification within the abscess wall suggests chronic infection (tuberculosis)
Psoas Abscess¶
The psoas muscle runs from T12 to the lesser trochanter of the femur, providing a pathway for infection to track distally:
- The abscess may extend from the lumbar spine into the pelvis, groin, or thigh
- CT with contrast is the best modality for mapping the full extent
- Can be primary (hematogenous, associated with IVDU or immunosuppression) or secondary (from spondylodiscitis)
Clinical Pearl
A psoas abscess in the absence of obvious spondylodiscitis should still prompt evaluation of the lumbar spine — the vertebral infection may be subtle on initial imaging. Conversely, when spondylodiscitis is identified, always evaluate the psoas muscles for abscess extension, as undrained psoas abscesses are a common cause of treatment failure.
Management¶
- Percutaneous CT-guided drainage — First-line for accessible abscesses; allows culture and sensitivity testing
- Antibiotics — IV antibiotics directed by culture results
- Surgical drainage — For complex, multiloculated, or inaccessible abscesses
- Treatment of underlying spondylodiscitis — Essential for preventing recurrence
Key Points¶
- Paravertebral abscesses usually arise from contiguous spondylodiscitis
- Rim enhancement on post-contrast MRI/CT is the hallmark
- Psoas abscesses can track distally from lumbar spondylodiscitis
- CT-guided percutaneous drainage is first-line treatment
- Gas within the abscess strongly suggests pyogenic infection
- Calcified abscess wall suggests chronic infection (tuberculosis)
References¶
- Expert Panel on Neurological Imaging, Ortiz AO, Levitt A, Shah LM, et al. ACR Appropriateness Criteria® Suspected Spine Infection. J Am Coll Radiol. 2021;18(11S):S488-S501. https://pubmed.ncbi.nlm.nih.gov/34794603/
- Ledbetter LN, Salzman KL, Shah LM. Imaging psoas sign in lumbar spinal infections: evaluation of diagnostic accuracy and comparison with established imaging characteristics. AJNR Am J Neuroradiol. 2016;37(4):736-741. https://pmc.ncbi.nlm.nih.gov/articles/PMC7960153/
- Torres GM, Cernigliaro JG, Abbitt PL, et al. Iliopsoas compartment: normal anatomy and pathologic processes. Radiographics. 1995;15(6):1285-1297. https://pubmed.ncbi.nlm.nih.gov/8577956/
- Al-Khafaji MQ, Al-Smadi MW, Al-Khafaji MQ, et al. Evaluating imaging techniques for diagnosing and drainage guidance of psoas muscle abscess: a systematic review. J Clin Med. 2024;13(11):3199. https://pmc.ncbi.nlm.nih.gov/articles/PMC11173313/
- Raghavan M, Palestro CJ. Imaging of spondylodiscitis: an update. Semin Nucl Med. 2023;53(2):152-166. https://pubmed.ncbi.nlm.nih.gov/36522190/
- Spondylodiscitis with psoas abscess. Radiopaedia.org. https://radiopaedia.org/cases/spondylodiscitis-with-psoas-abscess