Superficial hematoma is a collection of blood within subcutaneous or dermal tissue, usually occurring after trauma, surgery, or anticoagulant use. Ultrasonography is the primary diagnostic modality and the time-dependent echogenicity change of hematoma is a pathognomonic finding: acute hematoma is hyperechoic, subacute hematoma is mixed echogenicity, chronic hematoma is anechoic/cystic. No internal vascularity on Doppler — this avascular structure is critically important in differentiating hematoma from vascular tumors and malformations.
Age Range
5-90
Peak Age
40
Gender
Equal
Prevalence
Common
Hematoma forms when blood leaks into tissue due to vascular damage. In traumatic superficial hematoma, rupture of subcutaneous capillaries and venules causes blood to spread among subcutaneous fat tissue. In the acute phase (0-48 hours), erythrocytes are intact, creating high cell density and fibrin network — this causes hyperechoic appearance on US because numerous cell-fibrin interfaces create strong acoustic reflections. In the subacute phase (2-7 days), erythrocyte lysis begins, hemoglobin degradation products (deoxyhemoglobin, methemoglobin) are released, and clot retraction occurs — this heterogeneous process is reflected as mixed echogenicity (coexistence of hyperechoic and hypoechoic areas) on US. In the chronic phase (>1-2 weeks), cell destruction is complete, serous fluid becomes dominant and capsule formation may begin — appearing as homogeneous anechoic or hypoechoic cystic collection on US because particulate structures have dissolved and fluid has become homogeneous. During organization, peripheral granulation tissue may form and appear as peripheral vascularity on Doppler. On MRI, T1 signal depends on paramagnetic properties of hemoglobin degradation products: acute deoxyhemoglobin is T1 isointense, subacute methemoglobin is T1 hyperintense, chronic hemosiderin is T1/T2 hypointense.
The echogenicity change of hematoma on US directly reflects the hemoglobin degradation process: acute hyperechoic (intact erythrocytes) → subacute mixed (lysis + retraction) → chronic anechoic (serous fluid). This progressive change is pathognomonic and confirms the diagnosis when monitored with follow-up US.
Acute hematoma (0-48 hours) appears on US as a well or poorly defined, homogeneous or mildly heterogeneous hyperechoic mass. This appearance, distinctly more echogenic than surrounding subcutaneous fat, reflects the high cell density and fibrin network of fresh blood. Margins may be indistinct because blood has spread between tissue planes. Internal echo pattern may be homogeneous or finely granular.
Report Sentence
A homogeneous hyperechoic mass is seen in the subcutaneous tissue, consistent with acute hematoma in the clinical context.
Subacute hematoma (2-7 days) appears on US as a heterogeneous, mixed echogenicity mass. Hyperechoic areas (retracting clot) and hypoechoic/anechoic areas (lysing blood, serous fluid) coexist. Fluid-debris level may be seen — cell debris settles to the bottom due to gravity with clear fluid remaining on top. This heterogeneous pattern reflects the resolution process of the hematoma.
Report Sentence
A heterogeneous mixed echogenicity collection is seen in the subcutaneous tissue with fluid-debris level, consistent with subacute hematoma.
Chronic hematoma (>2 weeks) appears on US as an anechoic or hypoechoic, cystic-appearing collection. Posterior acoustic enhancement is seen — characteristic finding of fluid structure. A thin hyperechoic wall (capsule/granulation tissue) may surround it. Internal structure is homogeneous and resembles clear fluid. This appearance must be differentiated from simple cyst, seroma, or abscess.
Report Sentence
An anechoic collection with posterior acoustic enhancement is seen in the subcutaneous tissue, consistent with chronic/organized hematoma.
On color and power Doppler, no internal vascularity is seen in hematoma — this avascular structure is preserved in all phases and is the most important US finding for differentiating hematoma from solid vascular tumors. Thin peripheral vascularity (granulation tissue) may be seen around organized hematoma, but no internal flow. In active bleeding, jet-like flow may be seen — this is an indication for emergency surgical/interventional management.
Report Sentence
On color Doppler examination, no vascularity is identified within the collection, consistent with avascular hematoma.
On MRI T1, hematoma signal depends on hemoglobin degradation stage. Acute (deoxyhemoglobin): T1 isointense-mildly hypointense. Early subacute (intracellular methemoglobin): T1 hyperintense — this results from the paramagnetic effect of methemoglobin and is the most characteristic MRI finding of hematoma. Late subacute (extracellular methemoglobin): T1 hyperintensity persists. Chronic (hemosiderin): T1 hypointense peripheral rim. T1 hyperintensity is the cornerstone of hematoma diagnosis on MRI.
Report Sentence
The lesion demonstrates hyperintense signal on T1-weighted sequences, consistent with methemoglobin in the subacute hematoma stage.
Hematoma on MRI T2 shows variable signal depending on stage. Acute: hypointense due to deoxyhemoglobin effect (intracellular). Early subacute: hypointense due to intracellular methemoglobin. Late subacute: hyperintense due to extracellular methemoglobin. Chronic: markedly hypointense peripheral rim due to hemosiderin deposition — the 'hemosiderin rim' is the pathognomonic MRI finding of chronic hematoma.
Report Sentence
A hypointense rim suggesting hemosiderin deposition is seen at the periphery of the lesion on T2-weighted sequences, consistent with chronic hematoma.
Criteria
Fresh blood, intact erythrocytes, fibrin network formation, hyperechoic on US
Distinct Features
Usually painful and tender. May expand rapidly with anticoagulant use. May require emergency intervention if signs of active bleeding.
Criteria
Erythrocyte lysis, clot retraction, mixed echogenicity, fluid-debris level
Distinct Features
Size stable or beginning to decrease. Pain begins to subside. T1 hyperintense methemoglobin on MRI — most diagnostic stage.
Criteria
Serous fluid dominant, capsule formation, anechoic/cystic, hemosiderin deposition
Distinct Features
Usually asymptomatic. Organized encapsulated hematoma may require surgical drainage. Hemosiderin rim on MRI pathognomonic. Chronic calcified hematoma is a rare complication.
Distinguishing Feature
Venous malformation is compressible and fills with Valsalva (hematoma does not), may contain phleboliths, present since birth, does not show time-dependent echogenicity change.
Distinguishing Feature
Liposarcoma shows internal vascularity (hematoma is avascular), no time-dependent echogenicity change, contains persistent solid component, not associated with trauma history. Non-adipose enhancing component on MRI is pathognomonic for liposarcoma.
Distinguishing Feature
Foreign body granuloma shows linear hyperechoic structure (foreign body) + posterior shadowing/reverberation, no time-dependent echogenicity change, may have chronic inflammatory peripheral vascularity.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
3-monthThe vast majority of superficial hematomas resolve spontaneously with conservative treatment: ice, elevation, compression. Anticoagulant dose assessment may be necessary. Surgical drainage may be indicated for large or symptomatic hematomas. Aspiration or surgical excision may be needed for organized encapsulated hematomas. Recurrent hematomas without trauma should be investigated for underlying coagulation disorder. Resolution is confirmed with follow-up US — significant decrease expected in 4-6 weeks.
Most superficial hematomas resolve spontaneously and require no treatment. Large or symptomatic hematomas may require aspiration or surgical evacuation. Extra caution is needed in patients on anticoagulants. Hematomas developing without trauma history should be investigated for underlying coagulopathy or occult tumor.