Pseudomyxoma Peritonei 腹膜假黏液瘤

Key facts

Definition:Massive gelatinous accumulations often arranged in locular fashion in peritoneal cavity.

Classic imaging appearance:Loculated collections of mucinous fluid in peritoneal cavity.Pseudomyxoma peritonei is most commonly associated with benign,borderline,or malignant mucinous tumors of the ovary or appendix.Synchronous ovarian and appendiceal tumors are present in 90% of patients.

Imaging findings General features

Best imaging clue:Loculated collections of fluid of varying size scalloping liver and splenic surfaces and displacing bowel loops.

Pseudomyxoma peritonei initially seeds at sites of relative stasis and as large-volume disease develops,it fills the remaining spaces in peritoneal cavity and causes pressure effects on adjacent organs.It may extend into hernial orifices or the pleural cavity.

Transvaginal ultrasound (TVS) findings:Echogenic ascites reflecting the mucinous nature of fluid;(2)Unlike uncomplicated ascites,in which bowel loops are mobile and free-floating,in pseudomyxoma peritonei bowel loops are displaced and crowded due to mucin and fibrin in fluid.

CT findings：(1)Low-attenuation mucinous loculated collections in peritoneal cavity；(2)Areas of high attenuation,septa and calcification can be seen as volume of disease increases.

MR findings:Mucinous loculated collections in pseudomyxoma peritonei have low signal intensity on T1WI and high signal intensity on T2WI.

Imaging recommendations:Scalloping of liver and splenic surfaces and displacementofbowerloopsduetopressureeffectssuggestpseudomyxomaperitonei.

Differential diagnosis

Loculated ascites：Loculated ascites do not cause scalloping of liver and splenic surfaces Bowel loops float up toward anterior abdominal wall instead of being displaced centrally and posteriorly.

Pathology

General:(1)Pseudomyxoma peritonei results from peritoneal implants of columnar epithelium associated with progressive accumulation of mucinous ascites.

Fig 1 a)Coronal enhanced CT demonstrates numerous high attenuation masses in peritoneal cavity.Note that masses cause scalloping on liver surface(arrows).b)Axial enhanced CT shows appendiceal mucinous cystic adenoma(arrows)with dot-like calcification.

(2)Most commonly associated with benign,borderline,or malignant mucinous tumors of ovary or appendix and on rare occasions can be seen in tumors of colon,stomach,uterus,pancreas,common bile duct,urachal duct,or om phalomesenteric duct.(3)Tends to remain localized in the peritoneal cavity;however,extraperitoneal spread can be seen on rare occasions.

Gross pathologic,surgical features

Peritoneal cavity is filled with large amounts of gelatinous material with mucinous globules.

Microscopic features

Strips of single layer of mature cells filled with mucus.

Individual epithelial cells can be found floating within gelatinous material.

Clinical issues Presentation

Abdominal distention,pain and weight loss.Bowel obstruction in advanced cases.

Natural history

Recurrences are common.

Treatment

Surgical debulking is main treatment option.Role of intraperitoneal chemotherapy,radiotherapy or application of mucolytic therapy remains uncertain.

Prognosis

Patients with adenocarcinoma of the ovary or appendix have a worse prognosis than those with a benign neoplasm.

Overall 5-year survival is 40%-50%.

醫學詞匯注釋與簡要講解

gelatinous 膠狀的

locular 分隔狀、分房（腔）的

【prefix-】pseudo 假性的

pseudomyxoma 假黏液瘤

pseudocyst 假性囊腫

mucinous 黏液（性）的

synchronous 同時的，同步的

scalloping 扇貝狀的

hernial orifices 疝孔

最佳診斷線索：肝脾表面扇貝狀壓跡和腸管受壓移位、聚集

loculated 局限性、固定的

globules 珠、球

臨床表現：腹脹、腹痛、體重減輕；進展期出現腸梗阻。