What is a subungual hematoma?

Subungual Hematoma: Definition, Diagnosis, and Management

A subungual hematoma is a collection of blood beneath a fingernail or toenail, typically resulting from direct trauma or repetitive shear forces to the nail apparatus. 1 This condition causes pain due to pressure buildup between the nail plate and nail bed, but is generally benign when properly managed.

Causes and Presentation

• Subungual hematomas most commonly result from crush injuries (such as shutting a finger in a door) or direct trauma to the nail 1
• Athletes, particularly runners and dancers, may develop subungual hematomas from repetitive trauma 1
• The condition presents as a visible blood collection under the nail, which appears as a dark red, purple, or black discoloration 2
• Pain is the predominant symptom, caused by pressure from the accumulated blood 3

Diagnosis

• Diagnosis is primarily clinical, based on the characteristic appearance of blood collection under the nail following trauma 1
• It's important to differentiate subungual hematoma from other nail conditions such as:
  • Melanonychia (dark pigmentation of the nail) 2
  • Subungual melanoma (which may present with similar discoloration but different history) 2
  • Onychomycosis (fungal nail infection) 2
• When evaluating a suspicious nail lesion, consider whether there is a history of trauma, as this helps distinguish hematoma from other conditions 2

Management

Evacuation Techniques

• Trephination (nail drilling) is the standard treatment to relieve pressure and pain by creating a small hole in the nail plate to drain the blood 4, 5
• Several techniques are available for trephination:
  • Controlled nail trephination using a specially designed drill that penetrates the nail plate without damaging the nail bed 4
  • Extra-fine insulin syringe needle (29-gauge) insertion near the nail plate and into the hyponychium, which is particularly effective for smaller hematomas of the second, third, and fourth toenails 6
  • Electrocautery (but contraindicated with acrylic nails due to 41.5% risk of ignition) 5
  • Heated paper clip (traditional method) 5

Clinical Considerations

• Prompt evacuation of the hematoma provides significant pain relief and allows patients to resume activities more quickly 3
• The procedure should be performed with attention to sterile technique to prevent infection 4
• For patients with acrylic nails, avoid electrocautery trephination due to high risk of ignition (41.5% in studies) 5
• After drainage, monitor for signs of infection or abnormal nail regrowth 3

Special Considerations

• If the subungual hematoma covers >50% of the nail bed or is associated with nail fold or nail bed lacerations, consider evaluation for underlying fracture or more extensive nail bed injury 3
• In cases of significant trauma, radiographic evaluation may be necessary to rule out fracture of the distal phalanx 3
• Subungual hematomas should be distinguished from subungual melanoma, which requires biopsy and more extensive management 2

Follow-up

• Most uncomplicated subungual hematomas resolve without long-term nail deformity 3
• The damaged nail will typically grow out and be replaced by normal nail over time (approximately 6 months for fingernails and 12 months for toenails) 2
• Persistent pain, drainage, or abnormal nail growth should prompt further evaluation 3