Figures 18-20. (18) Imperforate anus. Lateral radiograph shows an imperforate anus below the "M" line drawn through the junction of the upper two-thirds and lower one-third of the ischium (perineal surgical approach). (19) Ectopic anus. Voiding cystogram demonstrates a recto-urethral fistula (arrow). (20) Imperforate anus. Lateral voiding cystogram demonstrates an air-filled distal rectal pouch (arrows) ending blindly below the "M" line, a finding indicative of a low lesion. There is no fistula opening in the terminal bowel.