After an intramuscular injection, a small firm nodule has developed in the gluteal region; what is the next step in management?

Management of Post-Injection Gluteal Nodule

Reassure the patient that this small firm nodule is most likely a benign post-injection granuloma or localized inflammatory reaction that will resolve spontaneously with conservative management over several weeks to months.

Initial Assessment and Diagnosis

The development of a small hard lump after intramuscular injection in the gluteal region most commonly represents one of three benign entities:

• Injection site granuloma – a localized inflammatory response to the injected material, typically appearing weeks to months after injection 1, 2
• Fat necrosis – particularly if the injection was inadvertently placed subcutaneously rather than intramuscularly 3
• Sterile abscess or hematoma – from local tissue trauma during injection 4

Key Clinical Features to Document

Obtain specific details about:

• Timing: When did the nodule first appear relative to the injection? Early nodules (2-4 weeks) are typically benign implant reactions, while true foreign body granulomas appear after several months 1
• Injection details: What medication was injected, volume, and technique used? 2, 3
• Associated symptoms: Is there pain, warmth, erythema, or systemic symptoms (fever, malaise)? 4
• Size and consistency: Measure the nodule dimensions and assess whether it is firm, fluctuant, or fixed to underlying structures 3

Immediate Management Strategy

Conservative Observation (First-Line)

For asymptomatic or minimally symptomatic nodules <3 cm without signs of infection, observation alone is appropriate 1, 3:

• No immediate intervention required
• Expected natural history: gradual resolution over 3-6 months in most cases 1
• Reassure patient this is a benign, self-limited process

When to Consider Imaging

Ultrasound is the preferred initial imaging modality if clinical uncertainty exists 2, 3:

• Indications for ultrasound: Nodule >3 cm, rapid growth, severe pain, or concern for abscess formation 3, 4
• Expected findings: Heterogeneous subcutaneous or intramuscular lesion with varying echogenicity; may show complex cystic/solid components 3
• Utility: Distinguishes solid granuloma from drainable abscess or hematoma 2, 4

Red Flags Requiring Urgent Evaluation

Proceed immediately to imaging and/or surgical consultation if:

• Signs of infection: Erythema, warmth, fluctuance, fever, or systemic toxicity suggesting abscess formation 4
• Neurovascular compromise: Development of sciatic nerve symptoms (foot drop, numbness, weakness) – this is a rare but serious complication requiring urgent evaluation 5
• Rapid enlargement: Significant growth over days to weeks 3
• Severe unremitting pain: Despite conservative measures 1

Treatment Options for Persistent Symptomatic Nodules

Intralesional Corticosteroid Injection (Preferred Medical Treatment)

If the nodule persists beyond 2-3 months and remains symptomatic, intralesional corticosteroid injection is the treatment of choice 1:

• Agent: Triamcinolone acetonide, betamethasone, or prednisolone 1
• Technique: Direct injection into the nodule under ultrasound guidance if available
• Repeat cycles: May be repeated in 4-week intervals until resolution 1
• Caution: Risk of skin atrophy with repeated injections; use lowest effective dose 1

Surgical Excision (Last Resort)

Surgery should be avoided as first-line therapy because foreign body granulomas grow fingerlike projections into surrounding tissue, making complete excision difficult 1:

• Indications: Only for cystic lesions with little tissue ingrowth, or failure of medical management after multiple corticosteroid cycles 1
• Timing: Consider only after 6+ months of conservative management 1

Special Considerations

Distinguishing from Serious Pathology

While rare, be aware that gluteal masses can occasionally represent:

• Soft tissue sarcoma: Particularly if no clear injection history or atypical imaging features 3
• Metastatic disease: FDG-PET can show false-positive uptake in injection granulomas, mimicking malignancy 2

If diagnostic uncertainty persists after imaging, ultrasound-guided core needle biopsy is preferred over excision 2, 3.

Prevention of Future Complications

Proper injection technique reduces risk 6:

• Use appropriate needle length (1-1.5 inches for gluteal injections in adults)
• Inject into the upper outer quadrant of the gluteus maximus to avoid sciatic nerve
• Aspirate before injecting to avoid intravascular injection
• Use subcutaneous fat pinch technique when appropriate to ensure proper depth

Common Pitfalls to Avoid

• Do not rush to surgical excision: This often leads to incomplete removal and recurrence due to fingerlike tissue ingrowth 1
• Do not assume infection without clear signs: Most post-injection nodules are sterile inflammatory reactions, not abscesses 1, 2
• Do not ignore neurologic symptoms: Sciatic nerve injury can present months after injection and may be associated with gluteal fibrosis 5
• Do not order extensive imaging workup for typical small nodules: Clinical diagnosis is usually sufficient for nodules <2 cm without concerning features 3