Avian appendix: Anatomic variant

Appendiceal anomalies, including appendiceal agenesis and appendiceal duplications, are extremely rare entities. In a study of 50,000 American appendicectomy specimens from 1924 to 1955, the rate of appendiceal duplication was 0.004% (two cases). This was half the rate of appendiceal agenesis of 0.008% (four cases). In 1962, Wallbridge classified appendiceal duplications into three different subtypes, noting less than 50 cases had been reported in the literature. He referred to a Type B1 appendiceal duplication as ‘bird-like’ or ‘avian type’ due to the arrangement being found normally in birds. Appendiceal duplication is an important, although rare, entity to identify given the possibility of appendicitis occurring in both appendices and the potential for resection of the wrong appendix. More recently Nageswaran et al. found 141 cases of duplex appendix had been published, including 2 cases of triple appendix. They concluded that an anteriorly placed appendix, away from the convergence of the taenia, or a normal appendix in the presence of convincing clinical or radiological signs of appendicitis should instigate a careful examination of the caecal pole and possible exploration of the retrocaecal space for appendiceal duplication.