The Vermiform Appendix and Its Pathologies

Abstract

The vermiform appendix is a muscular cylindrical structure originating near the junction of the cecum and ileum, averaging 9 cm (5-35 cm) in size. As the most mobile viscera, it can adopt several positions, the most common being the retrocecal position. Perceived as an atavistic organ lacking physiological relevance, the vermiform appendix appears to be involved in immune function, serving in the maturation of B lymphocytes and the production of immunoglobulin A, in endocrine function, excreting amines and hormones in the 2-3 mL of mucus secreted daily, and in digestive function, by storing beneficial bacteria from where they can recolonize the colon. With a lumen of about 6 mm, the vermiform appendix has a reduced storage capacity, so any blockage of the appendix with fecoliths (fecaliths), seeds derailed from the colon, or enlarged lymph nodes prevents drainage and intraluminal accumulation of secreted mucus. Unable to relax, the appendix wall severely limits its intraluminal volume, so mucus accumulation leads to inflammation of the appendix, known generically as appendicitis. In addition, the vermiform appendix may be the site of the development of neoplastic processes, which may or may not involve mucus production, some of which can significantly affect the standard of living and ultimately lead to death. In general, mucinous tumors may have a better prognosis than non-mucinous tumors. This review takes a comprehensive path, starting by describing the anatomy and embryology of the vermiform appendix and further detailing its inflammatory pathologies, pathologies related to congenital anomalies, and appendix tumors, thus creating an up-to-date framework for better understanding, diagnosis, and treatment of these health problems.

Keywords: adenocarcinoma; appendiceal tumors; appendicitis; vermiform appendix.

Figure 1

Stages of embryonic development of the vermiform appendix. (1). At about 4 weeks; (2). In the fifth week; (3). At about 12 weeks; (4). In the final stage.

Figure 2

The possible positions of the vermiform appendix, with respect to the ascending colon, main lymphatics, and iliac and psoas muscles.

Figure 3

Schematic cross-section of the appendix showing its layered structure.

Figure 4

Definition of primary tumor (T1–T4a) in appendix adenocarcinomas.

Figure 5

Definition of primary tumor (T4b) and regional lymph node (N1–N2), in appendix adenocarcinomas.