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Introduction:
Appendiceal Intussusception is a rare lesion associated with a number of causes. The radiologic and pathologic features are presented and discussed in this review.
Radiology Studies:
CT scan of the abdomen and pelvis shows an intraluminal polypoid mass in the base of the cecum. The mass is soft tissue attenuation and has an oblong shape. The mass measures 9 mm in diameter. There is no evidence of cecal or terminal ileal wall thickening. No normal appendix was visualized. There is no evidence of inflammation, abscess, or ascites. There is no evidence of pathologically sized lymphadenopathy in the abdomen or pelvis.
Discussion:
The appendix usually arises from the postero-medial cecal wall, 2.5-3 cm below the ileocecal valve at the confluence of the three cecal taeniae. It is suspended from the mesoappendix and may attach to the cecum in several ways. The adult appendix averages 7 cm in length and the external diameter ranges from 0.3 to 0.8 cm.
Intussusception of the appendix is a rare phenomenon and usually affects young boys although the patient range can vary from 1 to 75 years. Predisposing factors include thin mesoappendix, fetal conical shape of the appendix and the presence of mass lesions like endometriosis, carcinoid tumor, lymphoid hyperplasia, adenoma, and mucinous tumors.
The appendix may intussuscept in several ways: i) appendix tip into the proximal appendix, ii) appendix base into the cecum (polypoid presentation), iii) complete inversion (inverted appendix-as seen in the current case). The latter may also present as an area of umblication at the junction of taeniae coli on the cecal serosal surface. Patients can experience abdominal pain, nausea or vomiting.
The histology depends on the type and degree of intussusception and can vary from normal to significant. Inflamed, eroded, and ischemic changes are frequently seen. In recurrent intussusception, hyperplasia of the mucosa and muscular layers may be evident, which could possibly be mistaken for a hyperplastic/serrated cecal polyp. The inverted appendix structure may reveal a reversal of the histologic layers, i.e., the mucosa is on the outside and the deeper layers are internal; when an adenoma is the leading point, the lesion can appear to be a pedunculated polyp with the appendix forming the stalk. The intussuscepted appendix, therefore, should be examined for possible etiologies like endometriosis and neoplasms. In some cases, however, there may be no evident abnormality. Occasionally, the appendix may autoamputate following repeated intussusception and/or volvulus. In such cases, the presence of hemosiderin and cecal fibrosis in the absence of other cecal abnormalities indicate that a appendix was present at birth.
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The opinions and assertions contained herein are the private views of the authors, and are not to be construed as official, or as reflecting the view of the Department of the Air Force, Army, or Defense.
References:
1. Bockman DE. Functional histology of appendix. Arch Histol Jpn: 1983;46-271.
2. Forshall I. Intussusception of the vermiform appendix with a report of seven cases in children. Br J Surg: 1953;40-305.
3. Langsam LB, Raj PK, Galang CF. Intussusception of the appendix. Dis Colon Rectum: 1984;387-392.
4. Jevon GP, Daya D, Qizilbash AH. Intussusception of the appendix. A report of four cases and review of the literature. Arch Pathol Lab Med:1992;960-964.
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