The appendix is a vestigial hollow organ located in the cecum , in anatomically varied positions ( laterocecal, retrocecal, etc.) whose function is related to the reticuloendothelial system. It can become inflamed in a condition that traditionally has been considered an acute appendicitis ( but modernly there is an ongoing discussion about the existence of chronic appendicitis). The organ resembles a worm, thus it's anatomical descriptive term vermicular appendix, it is hollow and it's walls are composed of all the components of the wall of the bowel ( mucosa, muscularis mucosae, sub mucosa, muscularis and serosa) . Normaly there is secretions within the appendiceal lumen ( cavity) that are expelled towards the cecum(large bowel), however, if there is any factor obstructing the flow ( like a fecalith=hardened fecal matter) then the inflammatory process begins in what is known as an acute appendicitis.In this condition, the lumen ( inside hollow space) of the appendix usually becomes dilated due to the accumulaton of secretions and inflamatory cells.

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Note added at 10 hrs (2018-03-08 21:49:17 GMT)
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Yes Neil this is part of the description section of the pathologic anatomy report once the appendix has been removed.