Double Intestinal Atresia in Imperforate Anus: A Diagnostic Conundrum for Paediatric Surgeons

Abstract

Anal atresia, i.e. imperforate anus, is not an infrequently seen congenital anomaly with an average worldwide incidence of 1:5,000 live births.1 Congenital jejunoileal obstruction caused by atresia or stenosis is also a relatively common cause of neonatal intestinal obstruction, with an incidence of 1:400 to 1:1,500 live births.2,3 In contrast, colonic atresia is a rare cause of intestinal obstruction in neonates, with an incidence of about 1:20,000 live births.4 Most neonates with imperforate anus have one or more abnormalities that affect other systems. However, only two of 172 patients with imperforate anus were reported to have an intestinal atresia below the duodenum,5 and only two of 246 patients had an absent colon.3 It is thus extremely rare to see a patient with an imperforate anus and concurrent ileal stenosis and colonic atresia, as described by Asabe and Nagasaki in this issue of the Asian Journal of Surgery.6 The aetiology of intestinal or colonic atresia is not clearly understood. The current consensus is that there is an in utero mesenteric vascular catastrophe, such as volvulus, intussusception, incarceration, or strangulation secondary to hernias, and embolic or thrombotic events,7 which results in ischaemia and absorption of the necrotic bowel segment. The cause of imperforate anus is regarded as an event in the abnormal embryological development that results from defects in the shape of the dorsal (posterior) cloaca and an absence of the dorsal cloacal membrane.8 The lack of relationship between the causes of intestinal atresia and imperforate anus may, thus, explain the rarity of their co-existence. The level of rectal atresia in imperforate anus has traditionally been assessed by an invertogram, as in the reported case.6 In our institute, we rarely use the invertogram for the diagnosis of congenital anorectal malformation. Instead, magnetic resonance imaging (MRI) of the pelvis in these patients is