Mucocele of the appendix and pseudomyxoma peritonei.

Mucocele of the appendix is a descriptive term for an abnormal mucous accumulation distending the appendiceal lumen. Pseudomyxoma peritonei is characterized by mucinous ascites and implants throughout the abdominal cavity. Thirty-four cases of appendiceal mucocele and seven cases of pseudomyxoma peritonei of appendiceal origin on file at the Armed Forces Institute of Pathology were reviewed for their clinical, pathologic, and radiologic findings. These cases provided examples of the major radiologic findings reported in this entity. Previously unreported findings of dependent echoes within some mucoceles on sonography and pseudomyxoma peritonei tracking along the umbilical vein remnant or mimicking an intrahepatic mass are presented.