Diagnostic ultrasound characteristics of Morel-Lavallée lesions: Case and dataset analysis

Morel-Lavallée lesions (MLLs) are uncommon closed soft tissue injuries often arising from blunt trauma, characterized by a separation between the subcutaneous tissue and the underlying fascia, leading to fluid accumulation. This case report aims to enhance the understanding of ultrasonographic features associated with MLLs, supported by data from a patient with a confirmed MLL verified through surgical intervention or magnetic resonance imaging (MRI). A 45-year-old male presented with a history of lower leg trauma, sustained approximately 18 days prior to the initial ultrasonographic assessment. Comparative analysis was performed using a dataset of ultrasound imaging records from 37 patients with MLLs, confirmed through surgical or MRI evaluation between April 2019 and October 2023. Parameters examined included injury etiology, interval from trauma to ultrasound assessment, lesion location and dimensions, echotexture, presence or absence of a capsule, and color Doppler flow imaging (CDFI) findings for blood flow in and around the lesion. In this case, the patient exhibited a traumatic injury to the calf, a frequent site for MLLs, accounting for 18 of the 37 cases. The average lesion area was 15.9 cm², with the lesion appearing hypoechoic on ultrasound. Further assessment indicated heterogeneous echotexture within the lesion, presenting scattered and linear hyperechoic regions. A well-defined boundary encapsulated the lesion, consistent with findings in 34 of the 37 cases. CDFI showed an absence of internal blood flow within the lesion and minimal blood flow in the perilesional tissue, a pattern observed in 2 cases in the broader dataset. In conclusion, this report elucidates the typical ultrasonographic characteristics of MLLs, marked by hypoechoic presentation with a well-defined boundary and absence of internal or perilesional blood flow signals on CDFI. These findings contribute valuable insights into the sonographic diagnosis of MLLs, reinforcing ultrasound's role as a primary imaging modality for evaluating complex soft tissue injuries.