A 5-day-old male infant is diagnosed with anorectal agenesis. An ultrasound study reveals a rectourethral fistula. Which of the following is the most likely embryologic cause of this condition?

Anorectal agenesis is due to abnormal partitioning of the cloaca and is often associated with a rectourethral, rectovaginal, or rectouterine fistula. Failure of fixation of the hindgut can result in volvulus. Failure of the proctodeum to develop will result in an imperforate anus. Agenesis of the urorectal septum would most likely lead to a fistula but would not cause anorectal agenesis. Premature rupture of the anal membrane would not cause anorectal agenesis.