Summary: A 46-year-old man presented to the emergency department with complaints
of acute right lower abdominal pain and a mild fever for 6months. An
intraperitoneal, tender, ballotable, soft lump with smooth margins was
palpable in the right iliac fossa. High white blood cell counts of
13,000 cells/µl with neutrophil count of 82% were noted.
Ruptured giant mucocele of the appendix with pseudomyxoma peritonei
The differential diagnosis includes enteric duplication cyst, ovarian
cyst, mesenteric cyst, hydrosalpinx, lymphocele, abscess, hematoma,
etc.1, 2 ,3, 4
A computed tomography (CT) scan of the abdomen with oral and intravenous
contrast showed a moderately large mass lesion with thin enhancing
walls in the right iliac fossa region (Figure 1). There was a presence
of a rent (Figure 2) within the lateral aspect of its wall. Fluid-like
internal contents of the mass (17-20 HU) had spilled into the peritoneal
cavity, causing moderate ascites, and had extended along the inguinal
canals bilaterally adjacent to spermatic cords (Figure 3). An
exploratory laparotomy was performed and the enlarged, thin-walled
ruptured mucocele of the appendix was resected. A small adenomatous
polyp causing obstruction was found near the mouth of the appendix and
confirmed on subsequent histopathology.
A mucocele of the appendix results from the abnormal accumulation of
mucus within the lumen of the appendix. It is uncommon, with are ported
incidence of 0.2% to 0.3% in appendectomy specimens. There is a
female:male predominance of 4:1 and the mean age at presentation is
about 55 years.1,2 Clinical features include pain in the
right lower quadrant, a palpable abdominal mass, and intermittent
colicky pain.Approximately 25% of mucoceles are asymptomatic and
discovered incidentally on surgery. Obstruction is commonly
post-inflammatory, but it can also be due to fecoliths, congenital
obstruction of Gerlach’s valve, or extramural compression.
can be divided into 3 categories: (1) retention mucocele with
normal/hyperplastic appendiceal mucosa; (2) mucinous cystadenoma with
neoplastic epithelium similar to that seen in villous adenomas and
adenomatous polyps; and (3) mucinous cystadenocarcinoma with neoplastic
epithelium similar to that seen in adenocarcinoma of the colon.2,5
Rupture of the mucocele may result in pseudomyxoma peritonei, which is
characterized by implantation of mucinous epithelium on the peritoneum
and mucus accumulation within the peritoneal cavity, often leading to
adhesions and intestinal obstruction.2 Accurate pre-operative
diagnosis of unruptured mucocele of the appendix is extremely
important, since it may reduce the possibility of rupture and peritoneal
contamination during resection.1,2
A typical imaging
finding is a cystic mass in the expected region of the appendix. A
curvilinear calcification may also be seen in the right lower quadrant.
Barium studies may show an extrinsic impression on the cecum, terminal
ileum, or sigmoid colon. Ultrasound examination usually reveals an
oblong heterogeneous cystic mass with through transmission and posterior
enhancement. The degree of internal echogenicity varies with mucin
viscosity. Lesions are well-encapsulated unless they have ruptured.
reveals a low attenuation, well-encapsulated mass with smooth regular
walls and displacement of adjacent bowel loops. No peri-appendiceal
inflammation or abscess accompanying acute appendicitis is seen. There
are no unique imaging characteristics to distinguish between the three
groups of mucocele. However, cystadenomas and cystadenocarcinomas are
usually larger and rupture more readily
In a middle-aged or elderly patient with a lump in the right iliac
fossa, presenting acutely with pain, the possibility of ruptured
mucocele of appendix must be considered. Imaging shows a typical
thin-walled, cystic-appearing, enlarged appendix. A search for
obstructing neoplasm should be made and carcinoma of the colon ruled
out, which is found in 11% to 20% of patients.6
- Madwed D, Mindelzun R, Jeffrey RB Jr. Mucocele of the appendix: Imaging findings. AJR Am J. Roentgenol. 1992;159: 69-72.
- Dachman AH, Lichtenstein JE, Friedman AC. Mucocele of the appendix and pseudomyxoma peritonei. AJR Am J. Roentgenol. 1985;144: 923-929.
- Skaane P, Ruud TE, Haffner J. Ultrasonographic features of mucocele of the appendix. J Clin Ultrasound. 1988;16: 584-587.
- Kim SH, Lim HK, Lee WJ, Lim JH, Byun JY. Mucocele of the appendix: Ultrasonographic and CT findings. Abdom Imaging. 1998;23:292-296.
E, Rosai J, Pizzimbono CA, Wise L Mucosal hyperplasia, mucinous
cystadenoma, and mucinous cystadenocarcinoma of the appendix: A
re-evaluation of appendiceal “mucocele.” Cancer. 1973;32:1525-1541.
- Rampone B, Roviello F, Marrelli D, Pinto E. Giant appendiceal mucocele: Report of a case and brief review. World J Gastroenterol. 2005;11:4761-4763.