Fig. 5
From: Role of transperineal ultrasound in evaluation of patients with perianal inflammatory disorders
a 29-year-old male patient, with history of recurrent perianal fistula. TPUS in axial plane (a) shows a left-sided trans-sphincteric perianal tract, breaching the distal part of the deep external anal sphincter, crossing the left ischio-anal fossa. On coronal ultrasound images (b), the proximal extension of the left-sided tract could not be detected. In T2 oblique coronal image (c), the left trans-sphincteric tract is seen crossing the left ischio-anal fossa. In T2 oblique axial image (d), it was noted that it forms an intra-muscular abscess involving the left obturator internus muscle