What is the appropriate evaluation and management for a patient presenting with a palpable mid‑lumbar mass and back pain?

Evaluation and Management of Mid-Lumbar Mass with Back Pain

A palpable mid-lumbar mass with back pain is a red flag requiring immediate imaging with MRI of the lumbar spine without and with IV contrast to rule out infection, malignancy, or other serious pathology. 1, 2

Initial Clinical Assessment

Perform a focused physical examination looking for:

• Neurologic deficits (motor weakness, sensory changes, reflex asymmetry) suggesting nerve root or spinal cord compromise 1, 3
• Gait abnormalities indicating neurological involvement or mechanical instability 1, 3
• Fever or tachycardia suggesting infection (discitis, osteomyelitis, epidural abscess) 1, 3
• Abnormal spinal curvature or alignment indicating structural pathology 1, 3
• Palpable lymphadenopathy suggesting malignancy or systemic infection 1, 3
• Constitutional symptoms (unintentional weight loss, night pain) raising concern for malignancy 1, 3

The presence of a palpable mass itself constitutes a red flag that mandates advanced imaging regardless of other findings. 1, 4

Imaging Algorithm

First-Line Imaging: MRI with Contrast

Order MRI lumbar spine without and with IV contrast immediately. 1 This is the definitive study because:

• MRI is the primary imaging modality for detection and evaluation of intra- and paraspinal masses, with superior ability to localize the mass in relation to neural structures 1
• Contrast is essential when infection, inflammation, or neoplasm is suspected, and a palpable mass raises all three concerns 1, 5
• Precontrast images must be obtained to accurately assess enhancement patterns 1, 5
• MRI directly visualizes the spinal cord, ligaments, intervertebral discs, and paraspinal soft tissues better than any other modality 1, 3

Role of Plain Radiographs

While radiographs can identify lytic or sclerotic tumors, bony destruction, periosteal reaction, or soft tissue masses, they are insensitive and easily miss subtle findings. 1 In the presence of a palpable mass, radiographs alone are inadequate and should not delay MRI. 1

If radiographs are obtained first and are negative, this does not exclude serious pathology and advanced imaging remains mandatory. 1, 3

Alternative Imaging: CT with Contrast

CT lumbar spine with contrast is a second-line option only if MRI is contraindicated or unavailable. 1 CT with contrast demonstrates paraspinal abscesses with high sensitivity and guides surgical management, but is inferior to MRI for soft tissue characterization. 1

CT is useful for characterizing bone-origin masses and detecting mineralized matrix or calcifications, but should not replace MRI as the primary study for a soft tissue mass. 1

No Role for Other Modalities

• Bone scan with SPECT will not adequately evaluate paraspinal soft tissue masses or intraspinal pathology 1
• Ultrasound may confirm the presence of a superficial mass but cannot evaluate deep structures or spinal involvement 6
• CT myelography is invasive and only indicated if MRI is contraindicated and neurologic deficits are present 1

Differential Diagnosis Considerations

The combination of a palpable mass and back pain raises concern for:

Malignancy

• Primary spinal tumors (osteoid osteoma, osteoblastoma, ependymoma) or metastatic disease 1, 7, 8
• History of cancer increases probability of malignancy from 0.7% to 9% 3
• Benign tumors can cause persistent pain and deformity if misdiagnosed 7

Infection

• Paraspinal abscess, discitis, osteomyelitis, or epidural abscess 1, 2
• MRI with contrast is essential to evaluate for epidural extension and cord compromise 1

Other Pathology

• Soft tissue tumors, hematomas, or inflammatory masses 1, 6

Critical Management Principles

Do not initiate conservative management or physical therapy until serious pathology is excluded. 3 Continuing physical therapy in the presence of undiagnosed malignancy can lead to pathologic fracture progression, while delayed diagnosis of infection can result in sepsis or epidural abscess. 2

Urgent intervention is required if any of the following develop:

• Cauda equina syndrome (bladder/bowel/sexual dysfunction, saddle anesthesia, bilateral lower extremity weakness) requires emergent MRI and surgical consultation 2, 5
• Severe or progressive neurologic deficits (rapidly worsening motor weakness, multifocal deficits) mandate immediate imaging and neurosurgical evaluation 2, 5

Common Pitfalls to Avoid

• Do not rely on negative radiographs to exclude serious pathology in the presence of a palpable mass 1, 3
• Do not order MRI without contrast alone when a mass is present—contrast is essential for characterization 1, 5
• Do not delay imaging for a trial of conservative therapy—a palpable mass is itself a red flag requiring immediate investigation 1, 3, 4
• Do not assume the mass is benign based on clinical examination alone—benign tumors are easily misdiagnosed and can cause significant morbidity if untreated 7, 8

Follow-Up Based on Imaging Results

Once MRI results are available:

• If malignancy is identified, proceed with biopsy for tissue diagnosis and oncology referral 1
• If infection is confirmed, initiate appropriate antimicrobial therapy and consider surgical drainage if abscess is present 1
• If a benign tumor is found, surgical excision may be indicated depending on size, location, and symptoms 7
• If imaging is negative for serious pathology, reassess clinical findings and consider alternative diagnoses, but maintain high suspicion given the presence of a palpable mass 4