Abdominal imagingCase Type
Guillermo Unzué García-Falces, Héctor Lajusticia Andrés, Iván Vicaría Fernández, Nerea Alberdi Aldasoro, Paul López Sala, Loreto Ana de Llano Ibisate, Tamara Laxe VidalPatient
67 years, male
A 67-year-old man came with mild abdominal pain located in the right flank, abdominal distention, and significant weight loss. No fever or vomiting was described. Physical exam showed a 2 cm mass located in the right lower quadrant. Biochemistry revealed inflammatory parameters augmentation. CA 19.9 and CEA were also increased.
US exam showed multiple cholelithiasis in the gallbladder, and moderate quantity of free fluid in the abdominal cavity with echogenic foci and septations inside, displacing the hollow structures. 
On the right flank, a rounded well-defined mass with hypoechoic lumen was depicted. Thus, echogenic intramural foci were appreciated.
IVC CT scan showed hypodense and loculated ascites in the abdominal cavity with displacement of the vessels and lower abdominal structures and liver scalloping . Omental cake in the left hypochondrium was also appreciated . Thus, a heterogeneous nodule with avid enhancement was observed in the periumbilical region, probably corresponding to peritoneal nodule (Sister Mary Joseph’s nodule). 
On the right flank, a 2 cm rounded well-defined mass was depicted. It showed small mural and luminal calcifications. 
Final diagnosis was mucocele of the appendix and pseudomyxoma peritonei.
Appendicectomy, omentectomy and localized peritoneal resection were performed. Adjuvant chemotherapy treatment with FOLPOX was also given to the patient.
Mucocele of the appendix is defined by the distention of appendix lumen by mucus. Etiology is variable and includes retention cyst related to lumen obstruction, villous hyperplasia and mucinous cystadenoma and cystadenocarcinoma. Pseudomyxoma peritonei is characterized by an intraperitoneal rupture of a mucinous tumour, with mainly appendiceal origin.
Mucocele is most frequently asymptomatic, but it may present with abdominal pain, nausea, vomiting and palpable mass. Pseudomyxoma peritonei symptoms include heaviness, diffuse abdominal pain and gastrointestinal bleeding.
In US exam, mucoceles are located in the right lower quadrant and display hypoechogenic lumen and well-defined lobulated borders. Thus, they show mural calcifications. Size is variable. In CT scan, a well-defined round mass is appreciated next to the cecum with mural calcifications. Lumen density varies from fluid to soft tissue. Appendicolith is frequently seen. In US exam, pseudomyxoma peritonei is defined as heterogeneous hypoechoic poorly mobile fluid with septations. Scalloping of solid viscera and displacement of hollow structures may be associated. In CT Scan, pseudomyxoma peritonei displays hypodense, loculated ascites with scalloping of solid organs, calcifications, septations, displacement of the lower abdominal structures and vessels, fixation of small bowel loops and peritoneal nodules. Septations, calcifications and solid organs scalloping help to distinguish pseudomyxoma peritonei from peritoneal carcinomatosis.
As symptoms are non-specific; imaging is the first step in the diagnosis and management of this pathology. Prognosis depends on mucocele rupture. IVC CT scan is the most accurate imaging technique. Early diagnosis of pseudomyxoma peritonei is essential to allow early radical surgery in patients with peritoneal involvement to reduce recurrence. Treatment of non-ruptured mucocele is surgical. Appendicectomy is performed with complete resection of the meso-appendix and peritoneal fluid sampling for cytology. The treatment of pseudomyxoma peritonei is similar to all types: radical tumor reduction surgery with omentectomy, localized peritoneal resection and right hemicolectomy.
 A Fairise, C Barbary, AL Derelle, S Tissier, P Granger, F Marchal et al. Mucocele of the appendix and pseudomyxoma peritonei. J Radiol 2008; 89:751-62 (PMID: 18641562)
 Abraham H. Dachman, Joel E. Lichtenstein and Arnold C. Friedman. Mucocele of the appendix and pseudomyxoma peritonei. AJR 1985; 144:923-929 (PMID: 3885692)
 Hao Wang, Yong-Qi Chen, Ran Wei, Qing-Bing Wang, Bin Song, Cang-Yi Wang et al. Appendiceal mucocele: a diagnostic dilemma in differentiating malignant from benign lesions with CT. AJR 2013; 201:590-595 (PMID: 24059397)
 Rochelle P. Walensky, Anthony C. Venbrux, Carol A. Prescott and Floyd A. Osterman. Pseudomyxoma peritonei. AJR 1996; 167:471-474 (PMID: 8686628)
 G.Brent Mayes, Vicent P. Chuang and Richard G. Fisher. CT of pseudomyxoma peritonei. 1980 AJR 136:807-808 (PMID: 6261564)
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.