A 29-year-old male patient with a history of trauma to the right thigh, presented to our hospital after a motorcycle accident. The patient complained of painful swelling over the lateral aspect of the right middle thigh, progressively increasing in size.
MRI showed a well defined lesion in the lateral aspect of the right thigh, between subcutaneous fat and muscular fascia, measuring 19, 3 x 6, 9 x 5, 7 cm.
The lesion appeared heterogeneous hyperintense on STIR-weighted sequences and was predominantly hyperintense on T1-weighted sequences (compatible with subacute haemorrhage).
Internal septations and fluid-fluid levels were also seen.
Morel-Lavallée lesions are post-traumatic soft-tissue closed degloving injuries, in which the skin and subcutaneous tissues are separated superficially from the fascia to the underlying musculature, resulting in creation of a virtual cavity [1].
These lesions are particularly common in the trochanteric region and proximal thigh. In this region the dermis contains a rich vascular plexus that pierces the fascia lata. The disrupted capillaries may continuously drain into the perifascial plane, filling up the virtual cavity with blood, lymph and debris. An inflammatory reaction commonly creates a peripheral capsule, which may account for the self-perpetuation and occasional slow growth of the process [2; 3]. Other reported sites of involvement are the trunk, lumbar, pre-patellar and scapular regions.
Clinically, Morel-Lavallée lesions usually present as an enlarging painful mass with soft-tissue swelling and fluctuance in the region [4].
On ultrasound imaging, a Morel-Lavallée lesion may appear as an anechoic to hyperechoic mass, depending on the age of the haematoma. It may contain fat globules that appear as hyperechoic nodules along its walls. Computed tomography of a Morel-Lavallée lesion may show a fluid-fluid level resulting from sedimentation of cellular blood components and a capsule may surround the mass [5].
Magnetic resonance imaging is the preferred modality in these cases. Signal characteristics depend on the internal content and chronicity of the lesions. They may appear homogeneously hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences, resembling a fluid collection. The lesions may also appear homogeneously hyperintense on both T1 and T2-weighted sequences reflecting a high internal concentration of methemoglobin, a product of hemoglobin degradation, which is a characteristic of subacute haematoma. Variable T1 signal intensity with heterogeneous T2 hyperintensity may also be seen, as well as a hypointense peripheral ring representing hemosiderin and fibrous tissue [2; 3].
Once the lesion is identified, the haematoma should be evacuated and necrotic material debrided to avoid infection. Lesions which are not diagnosed early enough or are refractory to treatment, usually require open surgery [3].
Morel-Lavallée lesion of the right thigh
A relatively large, well-demarcated cystic soft tissue lesion is observed in the mid-lateral region of the right thigh. According to different MRI weighting sequences, the following characteristics are noted:
The lesion primarily involves the subcutaneous tissue and potential spaces around the fascia, with no obvious signs of bone involvement. Mild edematous changes or exudation may be observed in the adjacent soft tissues.
Based on the imaging findings and the patient’s history of trauma, the following diagnoses should be considered:
Considering the patient’s young age, clear history of trauma, lesion morphology, and the typical subfascial cystic separation features shown on MRI, the most likely diagnosis is a Morel-Lavallée lesion. If not managed in a timely manner, such lesions can persist for a prolonged period or enlarge repeatedly.
1. Treatment Strategy:
2. Rehabilitation/Exercise Prescription:
This report is a reference analysis based on the current imaging data and clinical description. It does not replace in-person diagnosis or professional medical advice. If you have any questions or if the condition changes, please consult a specialist or visit a hospital promptly.
Morel-Lavallée lesion of the right thigh
