Case contributed by Domagoj Kretic


Palpable lump in the distal right thigh with no other symptoms. The patient is a dog owner.

Patient Data

Age: 60 years
Gender: Male



In the distal part of right thigh is an ellipsoid, well-circumscribed lesion, measuring 15 x 6 mm. It appears to be situated inside or adjacent to the quadriceps fascia. Inside of the lesion there are curvilinear echogenic structures which are moving.


Videos showing curvilinear echogenic shapes undulating inside capsule.


Surgical gross pathological specimen which contains thin, 1mm in diameter, worm-like structures.

Case Discussion

Dirofilariasis in humans is caused by Dirofilaria roundworms. The main natural hosts for the three Dirofilaria species that most frequently cause disease in humans are dogs, wild canids (such as wolves and foxes) and raccoons. Humans are infected with Dirofilaria larvae through mosquito bites. Infection can result in nodules under the skin or conjunctiva. They may also present as lung granulomas (small nodules formed by an inflammatory reaction), which may appear as small nodules on chest radiographs, leading to further diagnostic procedures to exclude more serious diseases.

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