2. Peritoneal redistribution theory and carcinomatosis

Malignant spread of intraperitoneal tumours can occur via, local contiguous growth, noncontiguous spread along mesenteric planes, haematogenous, lymphatic or transcoelomic routes. Unlike the other routes, the transcoelomic pathway offers a rapid step change in facilitating metastasis form multiple sites from within the abdomen. The parietal peritoneum has both secretatory and absorptive functions. The omentum has an absorptive function. This has been exploited in fashioning omental flaps to minimise incidence of inguinal lymphocyst after lymphadenectomy or pelvic collection after exenteration.

The dynamics of peritoneal fluid is driven by secretion/adsorption by the peritoneum (in particular right diaphragmatic peritoneum), recesses formed by the peritoneal reflections, omental filtering, movement of diaphragm, negative pressure in the subdiaphragmatic region, motility of viscera on mesentry and the resultant fluctuation in pressure differential within the peritoneal cavity.

The 'redistribution phenomenon' was described by Sugarbaker in relation to pseudomyxoma peritonei [1]. In this process free floating malignant cells and other debris utilise the movement of peritoneal fluid (and the ascites produced) to become redistributed throughout the peritoneal cavity. This includes the lesser sac. The absorption and filtering of the peritoneal fluid by the greater and lesser omentum can result in debris and cells, including malignant cells, becoming adherent to the omentum. This may in time result in 'omental cake' noted in advanced ovarian cancer. Another major notable site of fluid absorption and disease conglomeration is the right hemidiaphragm. Gravitational distribution explains the deposits in the Pouch of Douglas, paracolic gutters and subhepatic recesses. The mobile organs such as small bowel are spared of deposits, early in the disease, whereas fixed retroperitoneal structures such as ascending/descending colon and gastric pylorus may be affected. This would necessitate resection of the organs.
