Revision 27 for 'Pseudomyxoma peritonei'

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Pseudomyxoma peritonei

Pseudomyxoma peritonei refers to intraperitoneal accumulation of a gelatinous ascites secondary to rupture of a mucinous tumor. The most common cause is a ruptured mucinous tumor of the appendix / appendiceal mucocoele 10.  

Occasionally, mucinous tumors of the colon, rectum, stomach, pancreas and urachal tumors 9-10 are implicated. There is some ongoing contention as to whether primary ovarian tumors are a frequent source in their own right, or whether in these cases the appendix is the primary site and the ovarian lesion is metastatic 2-3.

Pathology

The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well differentiated primary tumor 3.

Pseudomyxoma peritonei may be divided into two pathological subtypes which have etiological and prognostic significance 4.

  • peritoneal adenomucinosis
    • a peritoneal neoplasm composed largely of mucin associated with fibrosis with minimal cytologic atypia and mitoses
    • primary tumor is generally an adenoma
  • peritoneal mucinous carcinoma
    • characterized by proliferative epithelium, glands, nests, or individual cells with marked cytologic atypia
    • the primary is a mucinous adenocarcinoma

Not all cases fit neatly into these categories, and many patients have intermediate or discordant features.  

However a long term follow-up study 4 of 109 patients found 5 year survival rates were markedly different: 75% for the adenomucinosis group and 14% for the mucinous carcinoma group.  The intermediate/discordant group 5 year survival was 50%.

Radographic features

General

It is typically characterized by loculated collections of fluid causing scalloping of abdominopelvic organs.

Conventional radiography

May show evidence of ascites with centrally displaced small bowel loops and scattered punctate or curvilinear calcifications.

CT
  • low attenuation, often loculated fluid thoughout the peritoneum, omentum and mesentery.
  • scalloping of visceral surfaces, particularly the liver 5
  • scattered (curvilinear or punctate) calcifications may be frequently present 5
  • tends to remain localized to peritoneal cavity
Ultrasound 
  • echogenic peritoneal masses or ascites with echogenic particles which (unlike other forms of particulate ascites such as hemoperitoneum or pus in the peritoneum) do not move 6
  • the small bowel loops displaced medially.
  • may show scalloping of the liver, spleen and at times other organs
MRI

Reported signal characteristics of the collections include 8

  • T1: typically low signal
  • T2: typically high signal
  • T1 C+ (Gd): may show enhancement 12

Complications

  • advanced cases may cause bowel obstruction

Treatment and prognosis

This is a progressive and often fatal disease. Recurrent bowel obstructions are commonly due to the fibrosis and adhesions.

Treatment is surgical debulking, followed by infusion of intraperitoneal chemotherapy.

Differential diagnosis

General imaging differential considerations include

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