Pathophysiology of malignant ascites

In general, malignant ascites develops from metastasizing tumor cells that settle and spread in the peritoneal cavity (peritoneal carcinomatosis).

Spreading tumor cells in peritoneum as major cause for malignant ascites

Tumor growth eventually disrupts the normal regulation of intraperitoneal fluid flow and the maintenance of a steady state in the peritoneal cavity by simultaneously causing a greater fluid inflow as well as a reduced (lymphatic) outflow.

Based on the peritoneal spread of tumor cells, there are three major mechanisms that cause flow disturbance:

• Neovascularization
  Factors secreted by tumor cells, such as vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs), contribute to tumor neovascularization, which is associated with higher plasma influx.
• Increased permeability of capillaries
  VEGF also causes increased permeability of the tumor capillaries and has the same effect on the capillaries of the peritoneum. Consequently, the new cancer vessels as well as the vessels of the peritoneum contribute to an increased inflow of fluid.
• Lymphatic stomata obstruction
  Lymphatic stomata are obstructed by tumor cells leading to a decrease in lymphatic drainage (efflux) and consequently to accumulation of fluid in the peritoneal cavity.