What are the signs of infection in a ganglion cyst?

Signs of Infection in a Ganglion Cyst

The classic signs of an infected ganglion cyst include redness, warmth, tenderness, increased pain, swelling beyond the normal cyst boundaries, and the presence of soft tissue crepitus which strongly suggests gas-forming infection. 1

Clinical Evaluation for Infection

Cardinal Signs of Infection

• Erythema (redness) around the cyst
• Increased warmth of the overlying skin
• Tenderness that is significantly worse than the typical discomfort of a ganglion cyst
• Increased swelling or rapid enlargement of the cyst
• Fluctuance or change in consistency of the cyst

Systemic Symptoms

• Fever (temperature >38.5°C)
• Malaise or general feeling of illness
• Elevated inflammatory markers (if tested):
  • Increased C-reactive protein
  • Elevated white blood cell count (>11,000/L)

Critical Warning Signs

Soft Tissue Crepitus

The presence of soft tissue crepitus (crackling sensation when touching the area) without recent trauma, surgery, or puncture wound should be considered a reliable indication of infection until proven otherwise 1. This finding is particularly concerning as it indicates gas formation within tissues, which is highly suggestive of a serious infection.

Severe Pain

While ganglion cysts can cause discomfort, sudden onset of severe pain that is disproportionate to the clinical appearance may indicate infection or intracystic hemorrhage 2, 3.

Imaging Findings Suggestive of Infection

If infection is suspected, imaging studies may reveal:

• Ultrasound: Debris within the cyst, thickened wall, mobile septations, or perilesional inflammation 2
• MRI: Wall thickening, perilesional inflammation, fluid-fluid levels, or high signal intensity on diffusion-weighted images 2
• CT: Gas within the cyst (highly specific for infection) 2, 1

Diagnostic Algorithm

1. Initial assessment: Evaluate for cardinal signs of infection (redness, warmth, tenderness)
2. If infection suspected:
   • Check for soft tissue crepitus (highly specific for gas-forming infection)
   • Consider ultrasound as first-line imaging for superficial cysts 2
   • MRI with contrast may help distinguish infected ganglia from synovitis 2
   • CT is particularly useful if gas is suspected within the cyst 2, 1

When to Seek Immediate Medical Attention

Immediate medical evaluation is necessary if:

• Soft tissue crepitus is present
• Severe pain develops suddenly
• Systemic symptoms (fever, chills) develop
• Rapid enlargement or change in appearance occurs

Common Pitfalls

1. Misdiagnosis: Ganglion cysts are the most common soft tissue tumors of the hand and wrist 4, 5, but infected cysts can be mistaken for routine inflammation or vice versa.

2. Delayed treatment: Infected cysts require prompt intervention, unlike uncomplicated ganglion cysts which may resolve spontaneously in up to 58% of cases 6.

3. Inadequate imaging: While diagnosis of ganglion cysts typically relies on history and physical examination, suspected infection may require appropriate imaging to guide management 4.

4. Overlooking systemic symptoms: Fever and elevated inflammatory markers may indicate spread of infection beyond the local site.

Remember that infected ganglion cysts are relatively uncommon, but prompt recognition and treatment are essential to prevent complications and ensure good outcomes.