What is an appendiceal mucocele (appendcele)?

Appendiceal Mucocele (Appendcele): Definition and Management

An appendiceal mucocele is a rare condition characterized by distension of the appendix lumen due to abnormal accumulation of mucoid substance, which can be caused by various pathological processes including mucinous cystadenoma, mucinous cystadenocarcinoma, or simple obstruction of the appendix. 1, 2

Clinical Features and Presentation

• Appendiceal mucoceles are often asymptomatic and discovered incidentally during imaging studies, surgery, or appendectomy performed for other reasons 1
• When symptomatic, patients may present with right lower quadrant pain that can mimic acute appendicitis, along with nausea, vomiting, and occasionally a palpable abdominal mass 3
• The condition is more common in patients over 50 years of age and has a higher prevalence in women 4

Diagnostic Approach

• Preoperative diagnosis is crucial but challenging due to nonspecific symptoms 1
• Cross-sectional imaging with CT or MRI is recommended for patients with suspected appendiceal pathology, showing characteristic features of a cystic, tubular structure extending from the cecum 5, 6
• CT findings typically reveal a well-encapsulated cystic mass with low attenuation in the right lower quadrant 6
• Colonoscopy may show a characteristic "volcano sign" at the appendiceal orifice in some cases 6

Classification

Appendiceal mucoceles are classified into four histologic types:

• Simple mucocele (retention cyst)
• Mucosal hyperplasia
• Mucinous cystadenoma (most common type)
• Mucinous cystadenocarcinoma 2, 4

Surgical Management

• Surgical excision is the recommended treatment for appendiceal mucocele to prevent potential complications, particularly pseudomyxoma peritonei which can occur if the mucocele ruptures during surgery 4
• The surgical approach should be determined based on the size, location, and suspected histology of the mucocele:
  • Simple appendectomy is appropriate for simple mucoceles or cystadenomas without involvement of the base of the appendix 5
  • Right hemicolectomy is recommended for cystadenocarcinoma or when the base of the appendix is involved 5, 2
• Open surgery may be preferred over laparoscopic approach in cases of large mucoceles to minimize the risk of rupture 3
• Careful handling of the specimen is essential to prevent rupture and potential peritoneal seeding 4

Complications and Prognosis

• The most serious complication is pseudomyxoma peritonei, which can occur if the mucocele ruptures, resulting in peritoneal spread of mucin-producing epithelial cells 1, 4
• Prognosis depends on the histologic type and whether rupture has occurred:
  • Simple mucoceles and cystadenomas have excellent prognosis after complete excision 2
  • Cystadenocarcinomas have a more guarded prognosis, particularly if rupture has occurred 5

Surveillance

• Follow-up surveillance is recommended, particularly for patients with mucinous cystadenoma or cystadenocarcinoma 5
• Surveillance may include periodic imaging studies and tumor marker assessment (such as CEA) 5
• Patients over 40 years of age should undergo colonoscopy to rule out synchronous colonic neoplasms 5

Important Considerations

• Appendiceal mucoceles may be mistaken for other conditions such as acute appendicitis, ovarian cysts, or mesenteric cysts 1, 6
• Careful preoperative assessment and planning are essential to avoid intraoperative rupture and subsequent pseudomyxoma peritonei 4
• The surgical approach should prioritize complete removal without rupture, even if this requires conversion from laparoscopic to open surgery 3