Teaching Case

A 40-year-old woman, with abdominal pain and diarrhea. On clinical examination the patient had severe abdominal pain in the right lower abdominal quadrant, with signs of peritoneal irritation. She had fever of 37.4. Analytically; 13900 leukocytes with 80.1% of neutrophilia.

In the lower right quadrant US shows a tubular hypoechoic lesion, departing from the cecum, and ride retro-cecal [Figure 1].
The CT without intravenous contrast shows a hypodense tubular mass with calcified walls [Figure 2]. After intravenous administration of contrast, we see a strong enhancement of the walls of the mass and thickening and edema of the walls of the cecum, fat stranding of mesenteric fat adjacent to the lesion [Figure 3].

Mucoceles of the appendix are uncommon (0.3%) [1]. The term mucocele is a general macroscopic description that implies a dilated appendiceal lumen which can be caused by chronic obstruction of the appendix (simple mucocele) or result from mucosal hyperplasia and benign or malignant neoplasms of the appendix [2].
Mucoceles may be discovered incidentally, at the physical examination or abdominal imaging, or as a secondary surgical finding. Most patients present with acute or chronic right lower abdominal pain secondary to cystic distention of the appendix by mucus.
In association with acute appendicitis, a mucocele can become inflamed, and the clinical, US and CT findings can mimic those of acute appendicitis without mucocele. It is important to identify mucocele preoperatively because the surgical approach may be altered to avoid rupture of the mucocele resulting pseudomyxoma peritonei [3, 4].
The typical imaging finding of an appendiceal mucocele is a cystic mass in the expected region of the appendix. In sonography mucocele can be largely hypoechoic with an irregular inner wall caused by mucinous debris and varying degrees of epithelial hyperplasia [3-5]. Sonography is valuable also in demonstrating any pseudomyxoma peritonei when peritoneal scalloping of the hepatic outline and/or septate ascites can be found.
In CT, a mucocele appears as a well circumscribed, low-attenuation, spheric or tubular mass contiguous with the base of the cecum. The finding of curvilinear mural calcification suggests diagnosis but is seen in less than 50% of cases. Intraluminal gas bubbles or an air–fluid level within a mucocele suggest the presence of superinfection, which can occur in both benign and malignant mucoceles [3-5].