Appendix

Dr Mark Thurston and Dr Henry Knipe et al.

The appendix or vermiform appendix is a blind muscular tube that arises from the caecum, which is the first part of the large bowel.

The appendix arises from the posteromedial surface of the caecum, approximately 2-3 cm inferiorly to the ileocaecal valve, where the taena coli converge. It is a blind diverticulum, which is variable in length from 2-20 cm. The appendix lies on its own mesentery, the mesoappendix 1-2.

The tip of the appendix can have a variable position within the abdominal cavity 1-2:

  • retrocaecal (65-70%)
  • pelvic (25-30%)
  • pre- or postileal (5%)
  • an appendicolith is seen in 10% of patients, with 90% going on to develop appendicitis 1
  • the appendix can fill with contrast during a barium enema study

The normal appendix is visible in 60% of children and thin adults 1

A recently described dynamic ultrasound technique using a sequential 3 step patient positioning protocol can increase the visualisation rate of the appendix 3. In the study, patients were initially examined in the conventional supine position, followed by the left posterior oblique position (45° LPO) and then a “second-look” supine position. Reported detection rates increased from 30% in the initial supine position to 44% in the LPO position and a further increase to 53% with the “second-look” supine position. The authors suggested that the effect of the LPO positioning step improved the acoustic window by shifting bowel contents.

Vermis is the Latin word for worm, hence vermiform means worm-like. The word appendix originates from the Latin verb appendere meaning to hang from. 

Abdominal and pelvic anatomy
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Article information

rID: 22654
Section: Anatomy
Tags: cases, refs
Synonyms or Alternate Spellings:
  • Vermiform appendix

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