Expansion
Fluid moves upwards towards the diaphragm and is absorbed through diaphragmatic lymphatics
Expansion
The peritoneal cavity normally contains only about 50 ml of serous fluid, but there is a continuous circulation:
- Secreted by the peritoneal mesothelium
- Moved upwards along the paracolic gutters towards the diaphragm by the negative pressure generated on inspiration
- Absorbed through specialised stomata in the diaphragmatic peritoneum into subdiaphragmatic lymphatics, and thence to the mediastinal nodes and thoracic duct
This explains several clinical patterns:
- Subphrenic abscess following lower abdominal sepsis, since fluid travels up the right paracolic gutter
- Transcoelomic spread of malignancy, seeding the omentum, the diaphragm and the pouch of Douglas
- Peritoneal dialysis, which relies on the surface area (about 1 to 2 square metres) and this absorptive capacity
- Pleural effusion in ascites or Meigs syndrome, as fluid passes through diaphragmatic defects