Pseudoaneurysms of the medial plantar artery are rare. The authors describe a case of a pseudoaneurysm of the medial plantar artery of a child who had suffered a penetrating laceration injury. Diagnosis can be confirmed using Doppler ultrasound and magnetic resonance angiography. As an alternative to the conventional surgery technique, percutaneous Doppler ultrasound-guided thrombin injection is a safe and effective treatment.Keywords: pseudoaneurysm; medial plantar artery; thrombin; Doppler ultrasound. ResumoO pseudoaneurisma da artéria plantar medial é raro. Os autores relatam um caso de pseudoaneurisma da artéria plantar medial após lesão perfurocortante em criança. O diagnóstico pode ser confirmado por ultrassom com Doppler e angiorressonância magnética. Em contraponto à técnica cirúrgica convencional, o tratamento pode ser feito de maneira efetiva e segura com a injeção percutânea de trombina assistida pelo ultrassom com Doppler. Palavras C A S E R E P O R T Pseudoaneurysm treated with thrombin injectionPhysical examination revealed a pulsating mass, with a diameter of approximately 3 cm. The patient reported pain in response to palpation and the surrounding area was hyperemic, but there was no sign of active infection or bleeding. Femoral and distal pulses were present, there was no cyanosis, trophic lesions or decrease in capillary perfusion. Laboratory test results were within normal limits. Both sensitivity and motricity were preserved.Magnetic resonance angiography of the right foot showed a pseudoaneurysm with a rounded shape, regular outline and well-defined limits located in the plantar region, between the abductor muscles of the fifth toe and the short flexor of the toes. After intravenous administration of contrast medium, the pseudoaneurysm was easily visible and measured at around 24 x 21 x 21 mm. Deeper, the structure extended to the plantar neurovascular bundle and, following the perforation injury to the plantar fascia, there was edema of the short flexor muscles of the toes and of the abductor of the fifth toe, reaching the plantar fat pad and the cutaneous surface. All bones, tendons and ligaments were spared (Figure 1). These findings were corroborated by a Doppler ultrasound, which, in addition to the anatomic details, also showed the dynamics of the medial plantar artery pseudoaneurysm (Figure 2).