Pseudomyxoma peritonei refers to intraperitoneal accumulation of a gelatinous ascites secondary to rupture of a mucinous tumour. The most common cause is a ruptured mucinous tumour of the appendix / appendiceal mucocoele 10.
Occasionally, mucinous tumours of the colon, rectum, stomach, pancreas and urachal tumours 9-10 are implicated. There is some ongoing contention as to whether primary ovarian tumours 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.
The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well differentiated primary tumour 3.
Pseudomyxoma peritonei may be divided into two pathological sub-types which have aetiological and prognostic significance4.
- a peritoneal neoplasm composed largely of mucin associated with fibrosis with minimal cytologic atypia and mitoses
- primary tumour is generally an adenoma
peritoneal mucinous carcinoma
- characterised 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%.
It is typically characterisied by loculated collections of fluid causing scalloping of abdomino-pelvic organs.
May show evidence of ascites with centrally displaced small bowel loops and scattered punctate or curvilinear calcifications.
- 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 frequantly present 5
- tends to remain localised to peritoneal cavity
- echogenic peritoneal masses or ascites with echogenic particles which (unlike other forms of particulate ascites such as haemoperitoneum 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
Reported signal characteristics of the collections include 8
- T1 : typically low signal
- T2 : typically high signal
- C + (Gd) : may show enhancement 12
- advanced cases may cause bowel obstruction
Treatment and prognosis
This is a progressive and often fatal disease. Recurrent bowel obstructions are common due to the fibrosis and adhesions.
Treatment is surgical debulking, followed by infusion of intraperitoneal chemotherapy.
General differential considerations include
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