Imperforate Anus

• • High imperforate anus: Above the striated muscle complex or levator ani

  • Low imperforate anus: Rectal pouch descending into striated muscle complex and therefore have more favorable prognosis following reconstruction

  • Male patients most commonly have low imperforate anus with a perineal fistula or high anorectal agenesis with a rectoprostatic urethral fistula

  • Female patients most commonly have low imperforate anus and fistula from the blind-ending rectal pouch to perineal body or vaginal vestibule

  • 70% associated with other abnormalities such as the VACTERL abnormalities

  • -Vertebral abnormalities

    -Anal atresia

    -Cardiac abnormalities

    -Tracheoesophageal fistula and/or esophageal atresia

    -Renal agenesis and dysplasia

    -Limb (defects)

Epidemiology

• • 1/2500-1/5000 births

  • High imperforate anus 2-fold more common in males

Symptoms and Signs

• • Distended abdomen

  • Bilious emesis

  • Irritability

  • Failure to pass meconium

  • Fecaluria (if rectovesicular or rectourethral fistula)

  • High imperforate anus: Absence of dimple or absence of gluteal fold

  • Low imperforate anus:

  • -Presence of anal membrane, dimple, or fold (usually)

    -External fistula to perineum or vestibule

Imaging Findings

• • Plain lateral pelvic film: Shows gas filled rectal stump and relative location

  • Pelvic US: Shows relation of rectal stump to striated muscle complex

  • CT or MRI: Delineates the relation between the rectal stump and the striated muscle complex

• • Differentiating between low and high imperforate anus

• • History and physical exam

  • Abdominal pelvic x-ray

  • Pelvic US

  • Voiding cystourethrogram

  • Echocardiogram

  • Spinal MRI or US

  • Renal US

  • Upper GI

Surgery

• • Low imperforate anus: Cutback anoplasty (circumferential mobilization of anterior fistula and transposition to center of external anal sphincter)

  • High imperforate anus: Diverting colostomy until at least 12 months of age followed by (most commonly) posterior sagittal anorectoplasty and closure of rectourinary fistula

Complications

• • Leak or stricture, 5-10%

  • 30-80% have minimal problems with continence, remainder with significant problems with continence

Prognosis

• • 15-20% mortality secondary to other abnormalities

References