Endometriosis of the Appendix

Clinical History

A 40-year-old woman with a previous history of polycystic ovarian disease presented with abdominal pain lasting for 48 hours, both in the right lower quadrant and in the right lower back. Abdominal guarding was not displayed during physical examination. Blood test results were normal.

Imaging Findings

The US revealed a homogenous hypoechoic and thick-walled tubular lesion with regular forms located at the pericecal area; no internal vascularity was noted. The CT exam depicted a nonspecific focal mass in the distal third of the appendix without any evidence of inflammation. Endoscopy confirmed a 3 cm endoluminal protruding appendiceal mass displaying a hard consistency and an overlying smooth mucosa. Pathological examination of the fragments obtained by endoscopic biopsies was inconclusive and the patient was submitted to a surgical resection of the cecum. Pathological analysis of the specimen revealed the diagnosis of appendicular endometriosis. Further MRI depicted two foci of endometriomas at the right ovary.

Discussion

Endometriosis is defined as the presence of ectopic endometrium-like tissue outside the mucosal lining of the uterus. It is usually seen while exploring for pelvic pain, pelvic masses or infertility. It is estimated to affect about 15% of the fertile and 50% of the infertile women [1, 2]. Extragenital endometriosis refers to its ocurrence outside of the genital tract and is generally seen in the pelvic cavity. Its location and extent may however considerably vary. The intestinal tract is frequently affected and the involvement seen might be intraluminal and/or extraluminal.

Intestinal endometriosis may clinically present as regional enteritis, appendicitis, ischaemic enteritis or colitis, diverticulitis or a neoplasm. Appendiceal endometriosis is a rare clinical condition, often presenting as acute appendicitis. It may also present as intussusception, obstruction, lower intestinal bleeding and even perforation, especially during pregnancy [3]. The incidence rate of appendiceal endometriosis is less than 1% [4] and its clinical manifestations are usually not different from classical acute appendicitis [1, 3, 4]. The operative findings are often not specific [2], the diagnosis being mostly made after pathological examination of the excised appendix. A long history of pain in the right lower quadrant of the abdomen in a woman with an intermittent course, who has been known to have endometriosis is the sole clinical sign that can induce to suspect appendiceal endometriosis. However, one must remember that only 41% of these patients will complain of a “cyclic” right lower quadrant pain [1].

Ultrasound and pelvic MRI play a key role. Endometriomas classically manifest on ultrasound as hypoechoic and homogeneous lesions in the ovary (95%), uni or multilocular. The radiological presentation of appendiceal endometriosis usually has ancillary findings that suggest an abnormal obstructed appenditis, such as the degree of dilatation and lack of inflammatory findings. MRI provides additional and more specific information not only in endometrioma characterization (with the classic hyperintensity on T1-weighted images and loss of signal—“shading”—on T2-weighted images), but also in pelvic involvement by endometriotic foci, being extremely useful in demonstrating pelvic distortion caused by fibrosis and adherences [5]. One must bear in mind that the intestinal wall usually depicts as thickened, with low signal or density because of the hypertrophy of the muscular layer [6].

In conclusion, this rare condition is mostly diagnosed by histological examination following an appendicectomy performed for a different indication. A long history of right lower quadrant pain in a woman with proven endometriosis may evoke suspicion.

Differential Diagnosis List

Final Diagnosis

Endometriosis of the appendix

URL:	https://www.eurorad.org/case/13937
DOI:	10.1594/EURORAD/CASE.13937
ISSN:	1563-4086