84 IMPERFORATE ANUS
Frederick M. Karrer M.D., Denis D. Bensard M.D.

1. What is imperforate anus?

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It is a congenital defect in which the opening of the anus is absent or misplaced, usually fistulizing anteriorly to the perineum or genitourinary (GU) tract. Anorectal malformations range from slight anterior malpositioning of the anus to complex cloacal deformities. Children with anorectal malformations commonly have other congenital anomalies, such as the VACTERL association.

2. What is the VACTERL association?

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V Vertebral defects
A Anorectal malformations
C Cardiac anomalies
T Tracheoesophageal fistula
E Esophageal atresia
R Renal anomalies
L Limb defects

The incidence of renal anomalies increases with the severity of the imperforate anus-from 10% with low lesions to 75% with high lesions.

3. How do you determine the severity of the defect in boys?

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The key is whether the boy has a high or low lesion. Low lesions are characterized by a fistula to the perineum somewhere along the midline raphe between the anus and the urethral meatus. After 24 hours, most infants with low lesions demonstrate meconium at the fistula. Other signs of a low lesion include white “pearls” along the raphe or a raised loop of skin, the so-called bucket-handle deformity. Boys with high lesions typically have flat buttocks without a good buttocks crease and may have meconium at the urethral meatus or apparent on urinalysis.

4. How is the lesion assessed in girls?

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Most affected girls (> 90%) have a rectovestibular or rectovaginal fistula, which usually can be determined by careful perineal examination. Girls with cloacal deformities (i.e., one orifice) have a high incidence of GU obstruction such as hydrocolpos or bladder obstruction. In low lesions, the anal opening is displaced anteriorly on the perineum. The normal location of the anus is halfway between the vaginal orifice and the coccyx.

5. How are infants with anorectal malformations treated?

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Infants with high lesions should be managed initially with a sigmoid colostomy and later with a pull-through procedure called posterior sagittal anorectoplasty. Infants with low lesions usually can be managed with immediate anoplasty or dilatation and delayed repair.

6. What is a posterior sagittal anorectoplasty (PSARP)?

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PSARP is a procedure performed through a longitudinal incision in the midline of the perineum, which permits visualization of the pelvic musculature and sphincters and clear exposure of the rectum and fistula. After closure of the fistula, the rectum is repositioned within the sphincteric muscle complex, and a neoanus is created.

7. What are the results after surgical reconstruction?

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Continence, defined as voluntary bowel movements with no soiling, depends on the type of lesion. Continence approaches 100% for low lesions but is rare with the highest lesions such as cloaca deformities in girls or bladder-neck fistulas in boys. Constipation is present in almost 50% of patients but is more frequent with the simpler defects.
KEY POINTS: IMPERFORATE ANUS

1. Imperforate anus is a congenital defect in which the opening of the anus is absent or misplaced, usually fistulizing anteriorly to the perineum or genitourinary tract.
2. Infants with high lesions should be managed initially with a sigmoid colostomy and later with a pull-through procedure called posterior sagittal anorectoplasty.
3. Infants with low lesions usually can be managed with immediate anoplasty or dilatation and delayed repair.

References
BIBLIOGRAPHY
1. deVries PA, Pena A: Posterior sagittal anorectoplasty. J Pediatr Surg 17:638-643, 1982. Medline Similar articles
2. Jones NM, Humphreys MS, Goodman TR, et al: The value of anal endosonography compared with magnetic resonance imaging following the repair of anorectal malformations. Pediatr Radiol 33:183, 2003. Medline Similar articles
3. Kluth D, Lambrecht W: Current concepts in the embryology of anorectal malformations. Semin Pediatr Surg 6:180-186, 1997. Medline Similar articles
4. Pena A: Anorectal malformations. Semin Pediatr Surg 4:35-37, 1995. Medline Similar articles
5. Pena A, Hong A: Advances in the managemant of anorectal malformations. Am J Surg 180:370-376, 2000.
6. Sarin YK, Sinha A, Gupta A: High anorectal malformation in boys: Need for clarity of definition and management. J Pediatr Surg 37:1637, 2002. Medline Similar articles