A mucocele of the appendix is defined as dilatation of the appendiceal lumen secondary
to a variety of underlying pathological processes. Its presentation as pyrexia of
unknown origin (PUO) has not been reported before. A 65-year-old man presented with
a 3-month history of high-grade fever. Clinical examination and initial work-up for
PUO was unremarkable. Contrast-enhanced abdominal computed tomography detected a well-defined,
smooth, hypodense lesion at the base of the cecum ([Fig. 1]). A smooth filling defect, 1.5 cm × 1.5 cm in size, was seen on barium meal and
follow through ([Fig. 2]). At colonoscopy, a smooth, indentable bulge (1.5 cm × 1.5 cm) was seen in the base
of cecum with normal overlying mucosa ([Fig. 3]); the appendiceal opening was not visualized. When we took a biopsy from the lesion
there was a gush of mucopurulent fluid. Culture of this fluid yielded growth of Gram-negative
bacteria and anaerobes. The lesion collapsed and the appendiceal opening was then
visible and found to be normal ([Fig. 4]). Biopsies of the lesion showed chronic inflammation. After drainage of the fluid
and treatment with appropriate antibiotics the patient showed a dramatic reduction
in his fever. Histopathological examination of tissue obtained from the appendectomy
that was performed 2 weeks later was reported as suggestive of mucocele ([Fig. 5]).
Fig. 1 Computed tomographic scan of the abdomen, showing a smooth, rounded indentation on
the medial wall of the cecum.
Fig. 2 Barium study showing indendation at the base of the cecum, along the medial wall.
Fig. 3 Colonoscopy revealed a smooth, rounded lesion in the cecum; the appendix is not visualized.
Fig. 4 On biopsy, there was a gush of mucopurulent fluid and the lesion disappeared. The
appendix can now be clearly seen in this colonoscopic view, suggesting that the lesion
was related to the appendix.
Fig. 5 A low-power photomicrograph of the appendix, showing a mucinous type of epithelium.
The lamina propria, submucosa, muscularis mucosa, and serosa are interspersed with
pale eosinophilic material (mucin), separating the muscle fibers. As well as the mucin
there is dense and diffuse infiltration with chronic inflammatory cells (hematoxylin
and eosin stain, original magnification × 140).
An appendiceal mucocele may be detected incidentally at surgery, during imaging, or
at colonoscopy. Barium studies usually reveal a sharply circumscribed, smooth, submucosal
or extrinsic mass indenting the cecum without overlying ulceration [1]. An echo-poor mass with an onion-skin appearance is seen on ultrasound [2]. Computed tomography shows a hypodense lesion at the base of the cecum, indenting
it on the medial side [3]. The classic colonoscopic appearance is that of the “volcano sign”, where there
is a mound with a central appendiceal orifice [4].
Colonoscopy has been of limited use for appendiceal disorders. This is possibly the
first time that it has had a therapeutic role. This case exemplifies the detection
and management of an appendiceal mucocele presenting as a PUO.
Endoscopy_UCTN_Code_CCL_1AD_2AG
