Duplex appendix

Last revised by Daniel J Bell on 3 Feb 2021

Duplex appendix is a rare anomaly of the appendix and is usually discovered incidentally during surgery for appendicitis.

Duplication of the vermiform appendix is extremely rare. It is found in only 1 in 25,000 patients (incidence ~0.004%) operated on for acute appendicitis. Although duplication anomalies are uncommon, they have clinical and medicolegal significance.

A case is also reported in which a child had two appendectomies performed in a 5 month period.

When anomalies of the appendix are detected in childhood they are nearly always associated with severe intestinal, genitourinary or bony malformations, seen most often in conjunction with type B1 and C duplications.

This classification was proposed by Wallbridge in 1963, and at the time of writing (July 2016) remains the most widely accepted classification.

The Cave-Wallbridge classification divides appendix duplications into three types:

  • type A: single cecum with one normally localized appendix exhibiting partial duplication
  • type B: single cecum with two completely separate appendices and divided into two further subgroups
    • type B1 (‘bird-like type’): two appendices located symmetrically on either side of the ileocecal valve, resembling the normal arrangement in birds
    • type B2 (‘taenia coli’ type): one appendix arises from the cecum at the usual site, and the second branches at varying distances along the lines of the taenia from the first
  • type C: double cecum, each bearing its own appendix

Some authors have since described further types of complex multiplicity of the appendix. For example, "horseshoe appendix", "duplicated appendix and cecum"6, and "triple appendix" but these are often only diagnosed at surgery and not with imaging.

Possibilities to consider include:

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Cases and figures

  • Figure 1: normal
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  • Case 1
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  • Figure 2: type A
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  • Case 2: type A
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  • Figure 3: type B1
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  • Case 3: type A
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  • Figure 4: type B2
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  • Figure 5: type C
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