A 72-year-old woman presents with abdominal distention, fullness, and pain in the right iliac fossa.

Fig. 90.1 (A) Axial contrast-enhanced CT image shows the presence of a cystic lesion with thick walls in the right iliac fossa with surrounding fat stranding and free fluid. (B) Axial contrast-enhanced CT image of the liver in the same patient shows scalloping of the liver margins and ascites with peritoneal thickening.

Malignant mucocele of the appendix with pseudomyxoma peritonei

• Abscess
  
• Normal fluid-filled ileal loop
  
• Tuberculous ascites
  
• Peritoneal metastases
  
• Malignant ascites
  
• Ovarian cystic lesions
  
• Bowel perforation
  
• Peritoneal mesothelioma
  
• Meckel diverticulitis with perforation

Mucocele of the appendix is the accumulation of mucus with luminal distention of the appendix. The reported incidence is 0.2 to 0.5% of appendectomies. It can be benign or malignant. The benign variety results from occlusion of the appendiceal luminal opening into the cecum from a phlebolith or impacted feces. A malignant mucocele results from mucin-secreting adenocarcinoma of the appendix. Either a benign or a malignant mucocele can result in the development of pseudomyxoma peritonei on rupture.