Diagnosis

Imperforate anus

Etiology

Cause [dk9]

• The exact etiology of anorectal malformations is unknown

• Positive family history in ~1.4% of cases

• Specific syndromes: Currarino syndrome, Townes-Brock syndrome, and Pallister-Hall syndrome, trisomy 13, 18, and 21

Pathophysiology [fn5]

1. Cloacal membrane formation and subsequent breakdown into urogenital and anal openings should occur by 8 weeks' gestation

2. Defects in the formation or shape of the posterior urorectal septum account for many of the described abnormalities of imperforate anus

3. Associated anomalies: VACTERL (Vertebral, Anorectal, Cardiac, TracheoEsophageal malformations, Renal, Limb)

4. Cloacal exstrophy (1 per 100,000 live births) is the most severe cloacal anomaly and involves:

   • Anterior abdominal-wall defect in which two hemibladders are visible

   • Omphalocele

   • Imperforate anus

Complications [dk9]

• Dehydration

• Vomiting

• Aspiration

• Sepsis

• Surgical site infection

• Wound dehiscence

• Urinary tract infection

• Fistula

• Anal stenosis

• Rectal prolapse

Epidemiology

Incidence per 100.000 [n23][p2s][dk9]

Approach

• Prenatal ultrasonography [fn5]

• Blood test: blood cell count, serum electrolyte levels

• Urine: determine the presence of a rectourinary fistula

• Rectal examination

• Sacral radiography

• Distal colostogram

• Cystourethrography or cystoscopy

• MRI

• Echocardiography to rule out cardiac malformations

Treatment

1. Intravenous hydration [fn5]

2. Total parenteral nutrition

3. Broad-spectrum antibiotics if urinary fistula

4. Reconstructive surgery:

   • Initial colostomy if delayed definitive repair

   • Directly to definitive repair: Primary neonatal pull-through without colostomy

   • Posterior sagittal anorectoplasty (PSARP)

Differential diagnoses

Hirschsprung's Disease