Sonographic diagnosis of clinically unsuspected primary aneurysm of the medial marginal vein of the left foot.

Distinguishing primary aneurysms of the superficial venous system, and in particular, the medial marginal vein of the foot, from soft tissue tumors such as ganglia or angiomas may present a diagnostic dilemma Musculoskeletal ultrasound provides an opportunity to make clear distinctions and resolve such a dilemma. We report the case of a 34-year-old male who presented with a painless, slowly enlarging mass located on the dorsal aspect of the left foot and initially suspected to be a ganglion. Ultrasound evaluation was done using a Logic P9 GE machine, equipped with a 15 MHz high-frequency linear probe and Doppler. The findings are those of a dilated, non-thrombosed mass, with sonographic features of a venous aneurysm of the medial marginal vein. It measures about 2.1 cm in diameter and 3.4 cm in length and has the classic “yin-yang” Doppler flow pattern, which confirms the diagnosis. Although this condition is rare and poorly reported within the Nigerian population, a correct diagnosis through careful clinical examination and imaging is essential to determine the best course of treatment. This condition may be confused with ganglion cysts, tendon pathologies, and bursitis; the use of color flow and pulsed Doppler applications is recommended for easy distinction.