Pseudomyxoma peritonei is a clinical condition in which a large quantity of mucinous fluid or more gelatinous material accumulates in the peritoneal cavity. The term was first used by Werth in 1884 to describe a specific pathological entity that followed the rupture of a pseudomucinous cyst of the ovary, with subsequent implantation of the cyst contents on to the peritoneal surface followed by massive production of gelatinous material. Subsequently, Frankel in 1901 reported pseudomyxoma peritonei found at autopsy, presumed to have occurred following the rupture of a mucocele of the appendix. The term is now more generally used to describe the clinical condition, but it is not a single pathological entity with a uniform prognosis.

The mucinous material is an acid mucopolysaccharide (pseudomucin) that may be relatively cell free or may contain benign or frankly malignant appearing cells. It is generally thought that the pseudomucin is produced following implantation of cells from a primary tumour or organ. However, it is suggested that metaplasia of the peritoneal cells stimulated by the mucinous fluid may produce local spread and further production.

At present, the condition should always be regarded as potentially malignant, although identification of frankly malignant disease may be difficult and take several years. The myxomatous process is usually confined to the peritoneum with no lymphatic, parenchymal, hepatic, or extraperitoneal spread. Tumours of the ovary, in particular cystadenocarcinomas (16 per cent of which will produce pseudomyxoma peritonei) or less commonly cystadenomas, and appendiceal adenocarcinomas are the usual cause. Other sites of origin have been reported, including carcinomas of the uterus, colon, common bile duct, pancreas, and duplication cysts, and carcinoma of urachal cysts. Pseudomyxoma peritonei following rupture of an appendiceal mucocele is usually associated with an obstructing appendiceal adenocarcinoma. Benign mucoceles produced by experimental ligation of the appendix stump do not produce the condition following their perforation. This has led some to conclude that the obstruction has to be produced by a mucin-producing adenocarcinoma, and reports of the condition occurring after rupture of a benign mucocele may be incorrect.

The presentation is dependent on the underlying cause. The relatively benign behaviour of the tumour responsible often produces a prolonged clinical course: the patient presents with increasing abdominal distension and there is a marked disparity between the physical signs and the general well-being of the patient. Pain due to distension may occur but weight loss is unusual, and in most patients there is little impairment of their usual activities. Anaemia, elevation of the erythrocyte sedimentation rate, and hypoglycaemia have been reported. Pseudomyxoma is occasionally only identified at operation. Diagnosis may be suggested prior to laparotomy by a plain abdominal radiograph showing masses with annular areas of calcification. Ultrasound scanning shows multiple echogenic areas similar to multiseptate ascites but the bowel does not float in fluid. CT reveals dense homogeneous material with the intestines displaced to the side, unlike the situation in ascites.

A wide variety of possible treatments has been advocated, and the role of surgery is still contentious: randomized trials of comparative therapy are not available since the condition is very unusual. In some patients the disease runs a very benign course and aggressive therapy is inappropriate. However, there is evidence that surgical removal of the pseudomucin and underlying tumour, if necessary by repeated laparotomy, improves the prognosis. In particular, if the disease is localized, radical excision with peritoneal toilet offers the best prospect of cure. The use of 5 per cent dextrose solution during operation as a mucolytic agent may prevent recurrence. If surgery is incomplete, the prospect of a response to chemotherapy is improved if radical cytoreductive surgery has been performed. Intraperitoneal and systemic chemotherapy with a variety of agents including thiotepa, melphalan, cisplatin, 5-fluorouracil, mitomycin C, and chlorambucil, is well tolerated and is worthwhile. Although responsive to radiotherapy, the complications of total abdominal radiotherapy and the difficulties of surgery in these circumstances means that radiotherapy should be deferred until the response to chemotherapy has been assessed. However, radiotherapy should not be withheld if patients fail to respond to other treatment.

The prognosis of this condition is very variable, partially associated with the histological type of the underlying tumour but more so with the degree of dissemination of the myxomatous process. There is a very good outlook for prolonged symptom-free survival in patients with this condition, generally associated with radical surgery followed by adjuvant chemotherapy and radiotherapy.

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Fernandez RN, Daly JM. Pseudomyxoma peritonei. Arch Surg 1980; 115:409–14.