An imaging study that can help determine the diagnosis in cases of a deep non-palpable perirectal abscess includes a trans-rectal ultrasound.
Perianal abscess ultrasound
Perianal abscess CT
Perianal abscess MRI
Anal fistula x ray
Anal fistula ultrasound
Anal fissure physical examination
Anal fistula physical examination
Anal cancer ultrasound