An eighteen month old infant presents with difficulty passing stools. A grandfather and cousin reportedly required some type of bowel surgery in childhood. Digital rectal exam shows a somewhat narrowed but normally positioned anus. A computerized tomography scan is obtained that identifies a presacral mass. The next step in management in this patient with constipation is

A serum alpha fetoprotein
B barium enema
C magnetic resonance imaging of the spine
D suction rectal biopsy
E colonoscopy
A serum alpha fetoprotein
B barium enema
C magnetic resonance imaging of the spine
D suction rectal biopsy
E colonoscopy
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