General information
Pseudomyxoma peritonei is a rare disease of the abdominal or peritoneal cavity. There is a wide
spectrum of disease, ranging from the benign at one end to mucinous adenocarcinoma at the other.
The majority of cases result from a ruptured mucus secreting adenoma of the appendix. More rarely
the condition arises in other parts of the bowel, in the ovary in females and in rare cases in
other organs such as the bladder. The disease is due to the presence of a large amount of mucinous
fluid with the consistency of jelly in the abdominal cavity, and is often commonly referred to
as 'Jelly Belly'. The mucus is produced by cells that have spread and grown on the peritoneum
which lines the abdominal cavity.
Pseudomyxoma peritonei is often referred to as being a 'borderline malignant' condition. The
characteristics of a malignancy are that it spreads via the lymphatic system to the lymph nodes,
and by the blood vessels (vascular spread), thus reaching the liver, lungs, brain and other tissues.
Pseudomyxoma peritonei spreads only within the abdominal cavity in the majority of cases and does
not spread via the lymphatics or the blood stream. However it is not completely benign as it
continues to grow and eventually takes over the peritoneal cavity.
If untreated it will result in compression of the abdominal organs, making normal nutrition no
longer possible. The complications of malnutrition (predominantly infection such as pneumonia),
and complications following surgical treatment of the disease are common.
Pseudomyxoma peritonei of appendix origin
Tumours at the benign end of the spectrum tend to arise in the appendix, giving rise to the classical
pseudomyxoma peritonei syndrome. Pseudomyxoma peritonei of appendix origin is said to have an
incidence of around one per million per year. Common presentations of the disease are abdominal
distension, mucus in a hernia sac, perforated appendix, or an ovarian mass in females. Occasionally
it is found incidentally at laparotomy (explorative abdominal operation). The sequence of events is
thought to be rupture of a mucus-secreting adenoma of the appendix with release of viable (live)
adenoma cells into the peritoneal cavity. These cells spread widely within the peritoneal cavity,
they become attached to the peritoneum and release mucus, producing mucinous ascites (fluid and jelly).
The main concentrations of cells follow the flow of peritoneal fluid and tend to accumulate at
particular sites within the abdominal cavity.
Mucinous adenocarcinoma
Many patients who present with mucinous ascites suggestive of pseudomyxoma peritonei of appendix
origin turn out to have mucinous adenocarcinoma. Histology of the two conditions is quite similar
in that there are atypical (abnormal) cells with large mucinous pools. Often the differentiation
is only possible by the clinical behaviour of the disease and by detailed pathology of large volumes
of resected specimens. The condition is commonly confused with ovarian cancer in women, and
particularly with mucinous low malignant potential ovarian tumours. A small ruptured tumour of
the appendix can result in very large ovarian tumours and it is often quite difficult to rationalise
that a large ovarian tumour can be secondary to a small ruptured tumour of the appendix.
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