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When is it too late to drain a hematoma?

A hematoma is a collection of blood outside of a blood vessel. It occurs because of an injury to the wall of a blood vessel, allowing blood to seep out into surrounding tissues where it does not belong. Hematomas can occur anywhere in the body, but are most commonly seen under the skin or in muscles. Small hematomas may resolve on their own, but larger ones often require drainage to remove the trapped blood.

What causes a hematoma?

The most common causes of hematomas are:

  • Trauma – This includes injuries from falls, sports, car accidents, or being struck by an object. The impact can damage blood vessels and cause them to leak blood.
  • Surgery – Surgical procedures can damage blood vessels around the surgery site leading to postoperative hematomas.
  • Anticoagulant medications – Drugs that thin the blood or prevent clotting increase bleeding risk. People on these medications are prone to hematomas.
  • Blood vessel abnormalities – Weak blood vessel walls from conditions like Ehlers-Danlos syndrome make hematomas more likely.
  • Childbirth – Vaginal delivery can cause hematomas around the vagina, labia, or perineum.

Hematomas can form almost anywhere, but common sites include the brain, ears, abdomen, limbs, and under the fingernails.

When should a hematoma be drained?

Most minor hematomas resolve on their own within a few weeks. The body slowly reabsorbs the collected blood. However, some hematomas grow very large or persistent, requiring drainage. Here are some general guidelines on when drainage is recommended:

  • Large size – Hematomas over 4-5 cm often require drainage. Larger ones unlikely to reabsorb.
  • Compartment syndrome – Drainage prevents dangerous pressure buildup.
  • Nerve compression – Relieve pressure on compressed nerves.
  • Abscess risk – Drainage prevents infection if skin barrier broken.
  • Functional impairment – Drainage restores movement if joint/muscle function impacted.
  • Severe pain – Drainage provides pain relief.
  • Aesthetics – Drainage improves cosmetic appearance.

However, the optimal timing for drainage depends on the location of the hematoma.

Brain Hematomas

Hematomas in or around the brain require urgent drainage due to risk of permanent neurological damage. Guidelines recommend:

  • Emergency drainage within 4 hours for large hematomas with brain compression.
  • Drainage within 12 hours for hematomas over 3 cm.
  • Drainage within 24 hours for hematomas under 3 cm with mild symptoms.

Delaying drainage beyond these timeframes risks irreversible brain injury or death.

Spinal Hematomas

Spinal hematomas also require rapid drainage. Guidelines are:

  • Emergency drainage within 8 hours of symptom onset.
  • Delays beyond 8 hours have poorer prognosis for neurological recovery.

Muscle Hematomas

For hematomas within muscle compartments, drainage is recommended if:

  • Symptoms persist beyond 3-5 days.
  • Size exceeds 5 cm.
  • Compartment pressure testing shows high pressures.

However, there is no firm cutoff where drainage is considered “too late.” Even old organized hematomas several weeks out may benefit from drainage to relieve pain and restore function.

Joint Hematomas

For intra-articular joint hematomas, guidelines suggest:

  • Drainage within 7 days for optimal outcomes.
  • Beyond 2 weeks, the blood clots and is harder to drain.
  • Drainage up to 4-6 weeks may still offer some benefit.

When is it too late to drain a hematoma?

There is no absolute cutoff where draining a hematoma is deemed “too late” and offers no benefit. However, here are some general guidelines on when drainage is less likely to be helpful:

  • Brain hematomas untreated for over 72 hours.
  • Spinal hematomas untreated for over 24 hours.
  • Old, organized hematomas more than 6 weeks old.
  • Hematomas that have already scarred over or calcified.
  • Hematomas with no ongoing symptoms or functional impairment.

Draining chronic hematomas that are weeks or months old is rarely helpful. The body has already walled off and absorbed much of the blood. However, each clinical situation is unique. Experienced surgeons may still attempt drainage if ongoing symptoms warrant a trial of evacuation even in old hematomas.

Are there risks to delayed hematoma drainage?

Delaying necessary hematoma drainage carries multiple risks including:

  • Permanent tissue damage – Undrained hematomas exert pressure on surrounding tissues. This can lead to cell death and permanent scarring if prolonged.
  • Infection – Old, undrained hematomas are prone to developing bacterial infections.
  • Compartment syndrome – Muscle and nerve compression can cause severe pain and disability.
  • Joint contracture – Immobilization from untreated joint hematomas causes stiffness.
  • Delayed rehabilitation – Persistent hematomas prevent early mobilization and physical therapy.

While almost all hematomas will eventually resolve spontaneously, drainage can shorten recovery times and prevent complications when indicated.

When is it safe to leave a hematoma undrained?

Many minor hematomas do not require any intervention. It is generally safe to leave a hematoma undrained if it meets the following criteria:

  • Smaller size, under 5 cm diameter
  • No nerve compression or other urgent symptoms
  • Decreasing in size on serial exams
  • Patient has no bleeding disorders
  • Located away from critical structures like the brain/spine
  • No compartment syndrome or joint effusion
  • Does not cause significant functional impairment
  • Minimal to moderate pain

However, clinical judgment determines drainage needs. Some patients tolerate even large hematomas well, while others require drainage for smaller ones based on symptoms.

How is a hematoma drained?

The drainage technique depends on the hematoma’s location. Common techniques include:

  • Burr hole surgery – For brain hematomas, a hole is drilled through the skull to insert a drainage catheter.
  • Laminectomy – Spinal hematomas are drained through an incision in the back.
  • Incision and evacuation – Direct surgical cut down to open and drain accessible hematomas.
  • Aspiration – Insertion of a needle and syringe to draw out fluid from closed cavities like joints.
  • Angiographic embolization – Sealing off broken blood vessels feeding expanding hematomas.

After drainage, compressive dressing and bandages help prevent reaccumulation of blood. Hematoma evacuation may be followed by additional surgeries to control ongoing bleeding if necessary.

What happens if a hematoma is left untreated?

If a significant hematoma is left untreated, common outcomes include:

  • Gradual reabsorption over weeks to months as the blood liquefies.
  • Fibrous encapsulation with scar tissue forming around the clot.
  • Infection development, turning the hematoma into an abscess.
  • Calcium deposits forming over time, creating a calcified hematoma.
  • Chronic pain, nerve palsies, and loss of function if nerves compressed.
  • Joint stiffness or compartment syndrome if located near joints/muscles.
  • Skin necrosis and breakdown if cutaneous blood supply compromised.

Small, asymptomatic hematomas often safely reabsorb without intervention. However, untreated major hematomas can lead to many adverse effects. Periodic monitoring for resolution vs. complications guides management.


Determining when to drain a hematoma depends on multiple factors – location, size, symptoms, timing, and associated bleeding risk. While most minor hematomas spontaneously resolve, drainage is often required for larger collections to minimize permanent damage and promote early recovery. Urgent drainage within hours is essential for dangerous hematomas around critical structures like the brain and spine. Fortunately, even older chronic hematomas lasting weeks or months may still benefit from late drainage if impairing function or causing complications. Clinical judgment weighing expected benefits vs. risks guides the decision to intervene.