What is an appendicular mucocele?

What is Appendicular Mucocele?

Appendicular mucocele is a rare cystic dilatation of the appendix caused by accumulation of mucoid substance within the appendiceal lumen, occurring in only 0.1-0.3% of all appendectomy specimens. 1, 2

Pathological Classification

Appendicular mucoceles are histologically subdivided into four distinct types 2:

• Retention cysts - simple obstructive lesions 2
• Mucosal hyperplasia - benign proliferative changes 2
• Mucinous cystadenomas - the most common form, characterized by benign neoplastic epithelium producing large amounts of mucin 3, 4
• Mucinous cystadenocarcinomas - malignant lesions with invasive potential 3, 5

Clinical Presentation

The clinical presentation is highly variable and often nonspecific 1, 3:

• Asymptomatic in 25% of cases, discovered incidentally during surgery or radiological examination 2
• When symptomatic, may present with right lower quadrant pain mimicking acute appendicitis 1, 4
• Can present as a palpable, mobile, painless abdominal mass 3
• May mimic other conditions including appendicular plastron, cecal tumor, or even urolithiasis with colicky flank pain 1, 2
• Preoperative diagnosis is rare due to nonspecific symptoms 3, 5

Diagnostic Imaging

Ultrasound and CT scanning are the primary diagnostic modalities, though diagnostic accuracy varies 1, 5:

• Ultrasound can guide diagnosis in approximately 70% of cases (5 of 7 in one series) 1
• CT scan shows a large, tubular, cystic structure extending from the cecum 3, 5
• Imaging typically reveals a well-encapsulated cystic mass in the right lower quadrant 5, 2
• Colonoscopy may show external compression on the cecum but cannot definitively diagnose the lesion 2

Critical Complications

The most feared complication is pseudomyxoma peritonei, which occurs in approximately 10% of cases and can be potentially fatal if the mucocele ruptures. 1, 3

• Rupture leads to peritoneal seeding with mucin-producing cells 1, 3
• Risk of perforation increases with larger mucocele size 4
• Iatrogenic perforation during surgery must be meticulously avoided 1, 4

Surgical Management Algorithm

Once diagnosed, surgical treatment is mandatory due to the risk of perforation, malignant transformation, and pseudomyxoma peritonei. 1, 3

Treatment selection based on histology and size 1, 3, 5:

• Simple mucocele or mucinous cystadenoma: Appendectomy with negative surgical margins is adequate 5, 4
• Mucinous cystadenocarcinoma: Right hemicolectomy is recommended 3, 5
• Giant mucoceles: May require appendectomy with segmental cecal resection to ensure negative margins 4

Surgical approach considerations 1:

• Laparoscopic approach can be used in selected cases with strict safety measures to prevent iatrogenic perforation and peritoneal seeding 1
• Open approach remains appropriate, particularly for larger lesions or when malignancy is suspected 1, 3
• Intraoperative spillage of mucinous content must be avoided at all costs 1, 4

Important Clinical Pitfalls

Extreme caution during surgical manipulation is essential - any perforation or spillage can lead to pseudomyxoma peritonei 1, 4:

• Handle the appendix gently without grasping or compressing the mucocele 4
• Consider early conversion to open surgery if laparoscopic manipulation appears risky 1
• Ensure complete excision with negative margins on histopathology 4

Postoperative Surveillance

Following successful resection 4:

• Control colonoscopy and abdominal CT should be performed at 6 months post-surgery to detect any recurrence or pseudomyxoma peritonei 4
• Long-term follow-up is necessary given the potential for late complications 1