What is the likely cause of a blood‑filled blister on the labia and what is the appropriate management?

Blood Blister on Labia: Diagnosis and Management

Most Likely Diagnosis

A blood-filled blister on the labia is most commonly a vulvar hematoma resulting from trauma, with sexual intercourse being the most frequent non-obstetrical cause. 1

Clinical Presentation and Key Features

• Vulvar hematomas present with significant pain, swelling, and tenderness of the labia majora and/or minora, typically developing shortly after the traumatic event. 1
• The hemorrhagic fluid collection occurs in the female external genitalia and appears as a blood-filled, tense swelling. 1
• Trauma from vigorous sexual intercourse is the leading etiology in non-pregnant women, though other mechanisms include straddle injuries or direct blunt trauma. 1, 2

Essential Diagnostic Evaluation

Physical Examination Priorities

• Assess the extent of swelling, location (unilateral vs bilateral), and degree of tenderness to determine severity and guide management. 1
• Examine for signs of active bleeding, skin disruption, or associated injuries to the vagina, urethra, or perineum. 2
• Perform a careful speculum examination if tolerated to exclude vaginal extension or concurrent injuries. 2

Laboratory and Imaging

• Obtain complete blood count to assess for significant blood loss, particularly if the hematoma is large or the patient appears hemodynamically compromised. 1
• CT pelvis is the preferred imaging modality when the diagnosis is uncertain or to quantify the size of the hematoma and exclude deeper pelvic injuries. 1
• Laboratory studies help differentiate hematoma from abscess (which would show leukocytosis) or deep venous thrombosis. 1

Management Algorithm

Small, Stable Hematomas (< 5 cm, No Active Bleeding)

• Conservative management with ice packs, analgesia, and close observation is appropriate for small, non-expanding hematomas. 1, 2
• Instruct the patient to avoid sexual activity and strenuous activity until complete resolution. 2
• Schedule follow-up within 24-48 hours to reassess for expansion. 2

Large or Expanding Hematomas (> 5 cm or Increasing Size)

• Surgical evacuation in the operating room is indicated for large hematomas (typically > 150 cc) or those causing severe pain and functional impairment. 1
• The procedure involves incision, clot evacuation, identification and ligation of bleeding vessels, and placement of a drain if needed. 1
• Patients typically have an uneventful recovery and can be discharged within 24 hours post-operatively. 1

Hemodynamically Unstable Patients

• Immediate resuscitation with IV fluids and blood products if signs of hypovolemia are present. 2
• Urgent surgical consultation for operative management regardless of hematoma size. 2

Critical Differential Diagnoses to Exclude

• Bartholin gland abscess: presents with unilateral swelling at the 4- or 8-o'clock position of the posterior introitus with purulent features rather than blood-filled appearance. 3
• Friction or pressure blisters: these are typically smaller, asymptomatic, noninflammatory, and occur at sites of repetitive friction; they do not require cessation of activity if < 10% body surface area. 4, 5
• Infectious vulvar ulcers or erosions: consider herpes simplex virus, syphilis, or other STIs if ulceration rather than intact blood-filled blister is present. 6, 7
• Lichen sclerosus with ecchymosis: presents with porcelain-white plaques and areas of ecchymosis, but is a chronic condition with characteristic scarring rather than acute traumatic presentation. 4

Important Clinical Pitfalls

• Do not assume all labial swelling is infectious; trauma-related hematomas require different management than abscesses and do not respond to antibiotics alone. 1
• Do not delay imaging if the diagnosis is uncertain, as misdiagnosis can lead to inappropriate treatment and potential complications. 1
• Consider the possibility of sexual assault in cases where the history is inconsistent with the injury pattern, and provide appropriate trauma-informed care and resources. 2
• Monitor for delayed complications including infection of the hematoma, chronic dyspareunia, or fistula formation if not properly managed. 2

Follow-Up Care

• Re-examine within 24-48 hours for conservatively managed cases to ensure the hematoma is not expanding. 2
• Counsel patients to abstain from sexual activity until complete resolution and clearance by their provider. 2
• Provide reassurance that with appropriate management, most patients recover fully without long-term sequelae. 1