Mucocele of the Appendix: With Special Emphasis on Image Studies

In a review of 1,268 appendectomies from January 1984 to April 1989, ten cases were diagnosed as ”mucocele” by pathology. All these cases presented with a right lower quadrant (RLQ) mass or pain of variable duration except one whose mucocele was found incidentally during an operation for gastric cancer. One case revealed curvilinear and mottled calcification outlining a large mucocele on plain film of the abdomen. Abdominal ultrasonography in 7 patients showed negative finding in one case, a hypoechoic or anechoic tubular lesion with good transmission in two, an ovoid cystic lesion with variable internal echoes in dependent portion in two, intussusception in one and a periappendiceal abscess in one. Barium enema of 4 patients showed nonvisualization of the appendix but either filling defects with round smooth shape or external compression to the cecum were found. Fibercolonoscopy was performed in 4 cases, all were disclosed intrusions of mucocele from the appendiceal orifice. In one of them, the mucocele invaginated deeply and caused chronic appendico-cecal intussusception. Computed tomography was performed in one case, the mucocele showed a near-water-density tubular lesion with good enhancement of the wall after contrast injection. Though appendiceal mucocele is a rare clinical entity, it should be in the list of differential diagnosis of RLQ pain. With the disease in mind and advanced imaging modalities available, preoperative diagnosis is probable.