History: A 30-year-old pregnant woman presents to her primary care physician with abdominal pain. She underwent a pelvic ultrasound scan, which revealed a complex right adnexal structure, and an MRI scan was recommended.
Images are shown below. In order: sagittal ultrasound image of the right flank, coronal T2-weighted half-Fourier acquisition single-shot turbo spin-echo (HASTE) images, axial T2-weighted HASTE image, and an axial T1-weighted volumetric interpolated breath-hold examination (VIBE) fat-saturated image.
图像如下所示，分别为：右下腹矢状超声图像，冠状/轴位T2WI HASTE，轴位T1WI VIBE脂肪抑制。
Abdominal MRI demonstrates a tubular cystic structure adjacent to the cecum in the right lower quadrant of the abdomen measuring 24 x 30 x 95 mm. No wall thickening or nodularity is visualized. No surrounding edema or fluid is noted.
腹部MRI示右下腹一管状囊性结构，大小约24 x 30 x 95 mm，邻近盲肠，囊壁无明显增厚，未见壁结节，无周围水肿或积液。
- Appendiceal mucocele
- Acute appendicitis (abscess)
- Appendiceal tumors
- Cecal carcinoma
- Ovarian cystic mass
- Cystic fibrosis
Diagnosis: Appendiceal mucocele
WHAT IS THE UPPER LIMITS OF NORMAL FOR APPENDICEAL DIAMETER?
6 mm (the correct answer)
Appendiceal mucoceles are caused by abnormal accumulation of mucin in the appendix, resulting in dilatation. They can be caused by benign processes such as luminal obstruction, mucosal hyperplasia, appendiceal carcinoid, or mucin-secreting epithelial tumors.
At appendectomy, the reported prevalence of appendiceal mucoceles is 0.2% to 0.3%. They tend to be present in middle-aged adults. They can be associated with colonic adenocarcinoma or cystic fibrosis.
Most patients are asymptomatic. Occasionally, patients will present with tender right lower quadrant pain or a palpable mass. If appendiceal mucoceles rupture and the underlying cause is neoplastic, patients can end up with pseudomyxoma peritonei. The appendiceal mucocele can also be the lead point for an ileocolic intussusception.
- Barium enema: If a barium enema is performed in the setting of an appendiceal mucocele there can be nonfilling or partial filling of the appendix.
- Ultrasound: Appendiceal mucoceles are typically cystic masses with variable internal echogenicity. An onion sign, or sonographic layering within a cystic mass, is a highly sensitive feature.
- CT: Simple mucoceles appear as well-defined, low-density cystic masses in the right lower quadrant. There can be curvilinear calcifications within the wall. Mucinous cystadenomas are indistinguishable from simple mucoceles by CT.
- MRI: Appendiceal mucoceles are oval or spherical pericecal masses that are hypointense on T1-weighted imaging and bright on T2-weighted imaging.
The treatment of appendiceal mucoceles is surgical resection, usually a right hemicolectomy.