Appendiceal mucocele pathologically classified as appendiceal epithelial hyperplasia and preoperatively diagnosed by contrast-enhanced ultrasonography: A case report.

We report a patient with a mucocele with diffuse wall thickening diagnosed by transabdominal ultrasonography and contrast-enhanced ultrasonography. Transabdominal ultrasonography showed diffuse thickening of the entire appendix wall and an anechoic area that appeared to be fluid collected throughout the appendix lumen. However, the "onion skin sign" was not detected. Contrast-enhanced ultrasonography combined with superb microvascular imaging revealed abundant mucosal blood flow and no abnormal vascular network within the mucosa of the appendix wall. We preoperatively diagnosed a mucocele complicated by acute and chronic appendicitis, and ileocecal resection was performed. Macroscopic and microscopic findings of the resected specimens demonstrated that the appendiceal wall was diffusely thickened, with fibrosis and inflammatory cell infiltration, and that the appendiceal root rumen was narrowed with epithelial hyperplasia. No neoplastic changes were observed. The cause of the appendiceal mucocele was likely fibrosis and stenosis at the root of the appendix due to initial acute appendicitis.