Extensive iliopsoas muscle abscess resolution and return to soundness in a 7-week-old Arabian filly

A 7-week-old Arabian filly presented for a history of hindlimb gait abnormality and intermittent fever following a fall. Physical examination showed left hindlimb (LH) lameness and resistance to passive proximal limb flexion. Ultrasound revealed a large abscess in the left paralumbar region and computed tomography (CT) confirmed an expansile abscess within the left iliopsoas muscle. Ultrasound-guided abscess decompression followed by lavage and drain placement were performed under sedation with local anaesthesia. Streptococcus equi subspecies zooepidemicus was cultured from the abscess. The foal was managed with serial wound care, lameness evaluation and ultrasound examination. She was discharged after 35 days of hospitalisation following adequate wound healing and return to soundness with no signs of abscess persistence or recurrence. One-year follow-up indicated the filly healed well with minimal scarring, no visible lameness at the trot and only mild positive response to left hind full limb flexion. This case report describes the successful management of a large abscess in a highly unusual location in a young filly.