PMC6874504_01
(
A
) A 3-month-old boy with anorectal anomaly underwent colostomy at birth. (
B,C
) The contrast study "distal colostogram" performed in anteroposterior and lateral views showing blind rectal termination with no evidence of fistulous communication with the urinary tract (imperforate anus without fistula). Note: a radio-opaque mark has been placed indicating the site of anal dimple on the perineum (
arrow
). (
D
) Anteroposterior view of the plain X-ray showing the characteristic sacral defect (sacral scimitar). Note: the sacral notch cannot be detected in the lateral view of sacrum (
C
) and has been masked by the contrast in the anteroposterior view (
B
).
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Reexamination of his X-ray studies revealed a missed sacral notch in the plain X-ray ( Fig. 1D ) in addition to widening of the retrorectal space in lateral contrast film ( Fig. 1C ).
Follow-up magnetic resonance imaging (MRI) study performed after posterior sagittal anorectoplasty showing a residual presacral mass (*) in midsagittal T2-weighted image (
A
) and axial T2-weighted image (
B
). (
C
) Reoperation in the supine lithotomy position to remove the residual presacral mass (*); note: the incision is posterior to the neoanus (
white arrow
).
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 Later, a postoperative pelvic MRI was ordered that revealed residual presacral cystic lesion ( Fig. 2A, B ), with the absence of spinal cord anomalies. Initially, the lesion was obscured by its deep location and surrounding fat; however, deeper dissection directed toward the bony defect (sacral notch) enabled successful identification and excision of the lesion ( Fig. 2C ).
PMC6874504_02