In a patient two months after lumbar fusion who had a small postoperative hematoma and now has a CT‑identified seroma at the operative site with underlying spinal lipomatosis, should management be referral to the spine neurosurgeon/orthopedic spine surgeon or an ultrasound‑guided evaluation/aspiration?

Management of Post-Lumbar Fusion Seroma at Two Months

Refer the patient to the spine neurosurgeon or orthopedic spine surgeon who performed the original fusion for clinical evaluation and consideration of CT-guided aspiration if symptomatic, rather than ordering ultrasound as a standalone diagnostic step. 1

Rationale for Neurosurgical Referral

The ACR Appropriateness Criteria explicitly state that postoperative complications including seromas can develop throughout the postoperative course and cause extrinsic compression of the spinal cord, requiring specialist evaluation. 1 In patients who have undergone spinal surgery, fluid collections may represent seromas, pseudomeningoceles, hematomas, or epidural abscesses, and distinguishing these entities requires clinical correlation that only the operating surgeon can provide. 1

MRI without and with IV contrast is the gold standard for characterizing postoperative fluid collections, with 96% sensitivity and 94% specificity for spine pathology, and can help distinguish expected postoperative changes from infection. 1 However, the ACR notes that imaging findings of peripherally enhancing fluid collections can overlap between abscess and noninfected seromas, making clinical assessment paramount. 1

Why Ultrasound Alone Is Insufficient

• Ultrasound has been mentioned only anecdotally in fusion assessment literature and has not been rigorously evaluated for postoperative spinal fluid collections. 1
• The single report of ultrasonography for fusion status evaluation showed promising results but lacked validation against surgical exploration or other gold standards. 1
• CT imaging provides superior visualization of the operative site, hardware position, and bony fusion status, which is critical context when evaluating a fluid collection two months post-fusion. 1

Clinical Decision Algorithm

Step 1: Neurosurgical Clinical Assessment

The operating surgeon should evaluate for:

• Neurological deficits (motor weakness, sensory changes, bowel/bladder dysfunction) that would indicate cord or nerve root compression requiring urgent intervention 1, 2
• Signs of infection (fever, elevated inflammatory markers, wound erythema, induration, or tenderness) that would necessitate immediate surgical debridement 1, 2
• Symptomatic compression (new or worsening radicular pain, functional decline) versus asymptomatic incidental finding 3, 2

Step 2: Imaging Interpretation in Clinical Context

• The existing CT already demonstrates the seroma—additional ultrasound adds no diagnostic value 1
• MRI without and with IV contrast should be obtained if there is clinical suspicion for infection, as contrast enhancement patterns help distinguish abscess from sterile seroma 1
• It can be challenging to distinguish expected postoperative changes from infection on imaging performed within 6 weeks of surgery, and at two months this patient is just beyond that window 1

Step 3: Management Based on Symptoms and Stability

For symptomatic seromas with stable neurologic exam:

• CT-guided percutaneous aspiration is safe and effective, with 50% of patients experiencing resolution or substantial improvement of symptoms in one series 3
• This approach avoids additional surgery and has no reported peri- or post-procedural complications 3
• Aspiration should only be performed in hemodynamically stable patients with low suspicion for infection and stable neurologic exams 3

For asymptomatic seromas:

• Conservative management with clinical monitoring is appropriate, as demonstrated in pediatric spinal deformity series where all 25 seromas resolved spontaneously without operative intervention 4
• Seromas resolved after a mean of 12.2 days following presentation in conservatively managed cases 4
• Prophylactic antibiotics may be considered at the surgeon's discretion, though not universally required 4

For symptomatic seromas with neurologic deterioration:

• Emergent surgical evacuation is mandatory to reduce risk of permanent neurologic deficit 2
• Any acute change in neurologic status (new weakness, sensory loss, bowel/bladder dysfunction) requires immediate operative intervention 2

Critical Pitfalls to Avoid

• Do not assume the seroma is benign based on imaging alone—clinical correlation is essential, as even sterile seromas can cause pain, weakness, and numbness through mass effect 3, 2
• Do not delay neurosurgical consultation if the patient is symptomatic, as progressive compression can lead to permanent deficits 2
• Do not confuse seroma with other pathology—the history of lipomatosis is a red herring in this context, as spinal lipomas are congenital lesions that would have been present at the time of original surgery, not new findings at two months 5
• Do not order ultrasound as a diagnostic step—it has no validated role in evaluating postoperative spinal fluid collections and will delay appropriate management 1

Special Consideration: Lipomatosis Context

The patient's history of lipomatosis (presumably epidural lipomatosis) is a separate entity from the postoperative seroma. 1 Epidural lipomatosis contributes to degenerative spinal stenosis and may have been a factor in the original indication for fusion, but it does not change the management of an acute postoperative fluid collection. 1 Intramedullary spinal cord lipomas are congenital lesions that would not develop postoperatively. 5