Imperforate anus is a congenital malformation in which the rectum and anus do not properly develop, resulting in the absence of a normal anal opening. This condition occurs in approximately 1 in 5,000 live births and can be associated with other anomalies, such as VACTERL association.

VACTREL Syndrome:

  • Vertebral defects – e.g., small hypoplastic vertebrae or hemivertebra
  • Anal defects – anal atresia/imperforate anus
  • Cardiac defects – e.g., ventricular septal defects, atrial septal defects, or tetralogy of Fallot
  • Tracheoesophageal fistula
  • Renal defects – Complete or partial renal genesis (either unilateral or bilateral), other genitourinary system anomalies
  • Limb defects – missing or displaced digits, polydactyly, or syndactyly (i.e., webbed or fused fingers or toes)

History and examination

  • Newborns, often detected shortly after birth
  • Risk factors: Family history, maternal exposure to certain medications or toxins, VACTERL association
  • History: Absence of anal opening, inability to pass meconium, abdominal distension
SymptomsSigns
Absence of anal opening
Inability to pass meconium within 24 hours
Abdominal distension		Absent or abnormally positioned anal opening
Fistula between the rectum and perineum, urethra, or vagina

Differential diagnosis (D/D) & Complication

D/D:

  • Hirschsprung disease (Aganglionic colon segment, delayed meconium passage, but normal anal opening)
  • Anorectal malformation (Spectrum of disorders, may include imperforate anus)

Complications:

  • Infection
  • Urinary and fecal incontinence
  • Constipation

Investigation

  • Physical examination: Assess for the presence and location of the anal opening and associated fistulas
  • Imaging: Abdominal X-ray, ultrasound, and MRI to evaluate the extent of the anomaly and associated conditions
    • X-ray: Lateral film radiograph in prone position should be done to determine the location of the distal bowel air bubble from the anal dimple (marked by the placement of a lead marker). A distance of less than 1 cm usually indicates a low defect, and greater than 1 cm distance may indicate a high defect.
  • Echocardiogram and renal ultrasound to assess for VACTERL association

Admission criteria

  • Immediate admission for infants with confirmed or suspected imperforate anus for surgical evaluation and management

Management

Emergency management:

  • Nil per oral
  • Nasogastric tube placement for abdominal decompression ( Keep the opening of NG tube open)
  • Intravenous fluids

Medical:

  • Supportive care (fluid resuscitation, electrolyte management)
  • Start antibiotic (Inj Amoxicillin or Gentamycin)

Surgical:

  • Indication: Confirmed diagnosis of imperforate anus
  • Procedure: Staged surgical repair, including initial colostomy and definitive anorectal reconstruction (e.g., posterior sagittal anorectoplasty)

Advices

  • Postoperative care includes monitoring for complications and providing support for bowel and urinary function

Referral

  • Refer to a pediatric surgeon for confirmation of diagnosis and surgical management

References

  1. Levitt, M. A., & Peña, A. (2007). Anorectal malformations. Orphanet Journal of Rare Diseases, 2(1), 33.
  2. Bischoff, A., & Levitt, M. A. (2016). Congenital anorectal malformations. In Holcomb and Ashcraft’s Pediatric Surgery (6th ed., pp. 511-528). Elsevier.
  3. Cuschieri, A. (2001). Anorectal malformations in children: embryology, diagnosis, surgical management and prognosis. ANZ Journal of Surgery, 71(6), 361-374.