In short. Examination of the tension and the skin, blood counts, and imaging when a collection cannot be felt. What each finding changes about the plan.

Key points

  • Everything else supports those two findings.
  • Whether the swelling is tense tells the clinician whether there is a collection under pressure.
  • Whether the skin over it is healthy tells them whether the tissue above it is still being supplied.

The assessment of a suspected collection is quick and it is made mostly at the bedside. What follows describes its parts and what each one contributes, so that a patient knows what is being looked for and why.

The history

When the swelling was noticed, whether it is larger than it was, whether the pain is increasing, and what operation was performed and when. A photograph or a mark on the skin with a recorded time is the most useful thing a patient can bring, because it converts a description into a comparison. The history also establishes what may have provoked it: a rise in blood pressure, straining, lifting too early, or a medication that affects clotting.

The tension and the skin are the examination

Everything else supports those two findings. Whether the swelling is tense tells the clinician whether there is a collection under pressure. Whether the skin over it is healthy tells them whether the tissue above it is still being supplied. A soft swelling under healthy skin is observed; a tense swelling under skin that has changed is evacuated. The rest of the assessment exists to establish how and how urgently.

Examination, and what it can and cannot show

The clinician feels the swelling for tension, warmth, one-sidedness and pulsation, and examines the skin over it for colour, temperature, blistering and integrity. What the examination cannot do is assess a collection that sits deep to the muscle or in a plane that the hand cannot reach. That limit is not a failure of the assessment; it is the reason imaging exists.

Blood tests and imaging

A blood count shows how much blood has been lost into the collection, which matters where the swelling is large or where bleeding has continued, and clotting tests are added where there is a reason to suspect a problem with clotting. Ultrasound is used where the swelling is deep, where it cannot be assessed by hand, or where blood needs to be distinguished from fluid or from an infection. It shows the size and the plane of the collection, which changes how it is drained.

What the assessment is deciding

  • Whether the swelling is a collection under tension or ordinary post-operative swelling.
  • Whether the skin over it is still healthy, which decides how urgently it is dealt with.
  • Whether it can be aspirated, needs reopening, and what provoked it so that it does not recur.

You should leave knowing which of those was found and what happens next. Where a collection has been evacuated, it is worth also asking what provoked it, because a collection that recurs is usually one where the provoking factor was not addressed.

Related reading

Frequently asked questions

What does the examination actually look for?

Whether the swelling is tense or soft, whether it is warm, whether it is confined to one side, and whether it is pulsatile. Then the skin over it: the colour, the temperature, whether it is shiny or blistered, and whether it is intact. Tension and the state of the skin are the two findings that decide what happens next.

Why do I need a blood test?

A blood count shows how much blood has been lost into the collection, which matters where the swelling is large or where bleeding has continued. Clotting tests are added where there is a reason to suspect a problem with clotting, or where you take medication that affects it. Both change the plan rather than merely describing it.

When is a scan needed?

Where the swelling is deep, where it cannot be assessed by hand, or where it is important to distinguish blood from fluid, from an infection, or from ordinary swelling. Ultrasound shows the size and the plane of a collection and is used where the examination alone does not answer the question.

Risks & Limitations

  • A hematoma is blood collecting where it should not. The findings that matter are tension, growth over hours and a change in the skin over the swelling, not the size of the bruise.
  • Blood removed early leaves little trace. Blood left under pressure can compromise the skin over it and can organise into a firm mass that changes the contour permanently.
  • A collection is more likely after a rise in blood pressure, after straining or lifting too early, and in a patient who takes medication that affects clotting.
  • A wound that has been reopened for evacuation goes through a second period of healing, and the scar can settle less well than it would have done.
  • A collection can recur after it has been drained, which is why the provoking factors are reviewed and the restrictions on lifting are part of the treatment.
  • No assessment predicts a collection exactly, which is why the warning findings are taught to every patient rather than only to those at higher risk.

When to Seek Care

  • A swelling that is tense, tight and larger on one side, growing over hours &mdash — seek emergency care now.
  • Pain that is getting worse instead of settling, with a hard swelling &mdash — seek emergency care now.
  • Skin over the swelling turning dusky, shiny, blistered or cold &mdash — seek emergency care now.
  • Fresh blood leaking steadily through a wound that was dry — contact the team the same day.
  • Bruising that keeps spreading well beyond the operated area, or a wound that is coming apart.
  • Fever, spreading warmth or discharge around the wound, or feeling generally very unwell.

References & Further Reading

  • American Society of Plastic Surgeons (ASPS) - patient safety guidance on post-operative bleeding and collections
  • National Institute for Health and Care Excellence (NICE, UK) - guidance on surgical site care and on the management of post-operative complications
  • Cochrane Library - systematic reviews on drains and on wound management after surgery
  • British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS) - patient information on recovery after surgery
  • Chinese Medical Association Plastic Surgery Branch - clinical guidance

Medically reviewed by Shaoliang Wang, MD (王韶亮), Center Director, Plastic Surgery & Aesthetics Medical Center. Last reviewed: 19 September 2026.

This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.