E1896. Appendiceal Mucocele: A Slimy Condition
  1. Howayda Al Mrad; Texas Tech University Health Sciences Center
  2. Basel Yacoub; Texas Tech University Health Sciences Center
  3. Ioannis Konstantinidis ; Texas Tech University Health Sciences Center
  4. shaked Laks ; Texas Tech University Health Sciences Center
Appendiceal mucoceles are abnormal intraluminal collection of mucin in the appendix. It is a rare condition that accounts for less than 1% of all appendiceal pathology. They can be asymptomatic and are often discovered incidentally on abdominal imaging. When symptomatic, patients may present acutely or with a chronic nonspecific right lower quadrant pain. Large mucoceles may be palpable on physical examination and can cause a mass effect leading to obstruction of surrounding structures such as the right ureter.

Educational Goals / Teaching Points
Review the clinical presentations of appendiceal mucocele, describe multimodality imaging findings, discuss potential diagnostic pitfalls, share at least 10 clinical cases, including misdiagnoses in the setting of appendiceal mucocele, and build diagnostic confidence among radiologists-in-training.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Appendiceal mucoceles are broadly classified based on histology into non-neoplastic (simple mucocele and mucosal hyperplasia) and neoplastic (mucinous cystadenoma and mucinous cystadenocarcinoma). These subtypes cannot be reliably differentiated on imaging. In addition, biopsy is generally contra-indicated as it carries a risk of intraabdominal seeding. Mucoceles typically appear as rounded or tubular well-encapsulated cystic masses that are contiguous with the cecum. The presence of punctate or curvilinear calcifications in the mucosal wall supports the diagnosis and are in keeping with a chronic nature of the disease. Other nonspecific findings such as surrounding fat stranding, soft tissue thickening, or wall irregularity may also be present. Once the diagnosis has been made, it is important to assess for extraluminal mucin in the peri-appendiceal space, peritoneal cavity or surface of abdominal viscera which would be diagnostic of pseudomyxoma peritonei. The lumen of the mass is characteristically hypoattenuating on CT. It may appear hypo- or isointense on MRI’s T1 and is typically hyperintense on T2. On sonography, it produces a hypoechoic cystic mass with variable internal echogenicity. It is generally recommended that all appendiceal mucoceles be surgically resected to prevent complication, rule out malignancy and direct further management. It is particularly important to alert surgeons for the possibility of appendiceal mucocele for careful appendiceal inspection and to prevent intraoperative and postoperative complications. Appendectomy may be sufficient for localized disease, while right hemi-colectomy is indicated for extensive or histologically proven neoplastic cases. In addition, cytoreductive surgery and heated intraperitoneal chemotherapy are usually performed when there is rupture of the mucocele or peritoneal involvement to prevent locoregional recurrence.

Appendiceal mucocele is a rare condition that may be asymptomatic or present with vague abdominal pain. Complications of mucoceles may involve rupture that may lead to pseudomyxoma peritonei. Imaging is the mainstay of diagnosis and must rule out radiologic mimickers such as pelvic inflammatory disease, ovarian mass to appropriately direct clinical management.