Ultrasonographic features of Lucilia sericata-induced wound myiasis with foot gas gangrene: A case report.

Myiasis is the tissue infestation by fly larvae, mainly Dermatobia hominis or Lucilia sericata. Sonographic features of D. hominis myiasis are well described but not those of L. sericata with concurrent gas gangrene. A 57-year-old man presented with a 1-month left foot injury, swelling, and functional decline. Examination revealed left foot gangrene with the loss of the fifth toe, maggot infestation, and systemic inflammation. Laboratory tests revealed diabetes mellitus. Point-of-care ultrasound showed subcutaneous air, fluid-debris layers, and hyperechoic, moving structures consistent with larvae with posterior acoustic shadowing, and cobblestone appearance. Although it is often difficult to distinguish larvae from gas, as both appear hyperechoic, colour Doppler imaging revealed an associated twinkle artefact, differentiating larvae from gas. Computed tomography confirmed gas gangrene. Above-knee amputation was performed. Wound cultures showed Proteus mirabilis and Streptococcus dysgalactiae. DNA analysis identified L. sericata. We report the ultrasonographic features of L. sericata-induced wound myiasis with gas gangrene, underscoring the diagnostic value of point-of-care colour Doppler imaging in complex wound infections. In malodorous wounds with intralesional gas, the presence of self-propelling movement and posterior acoustic shadow, combined with a twinkle artefact on colour Doppler imaging should raise suspicion for myiasis as an important differential diagnosis.