Fig 2.

Peritoneum and diaphragmatic lymphatic drainage. The abdominal cavity is divided by the mesentery into two major compartments, the greater and lesser sacs. The lesser sac is bound by the retroperitoneum posteriorly, the stomach and greater omentum anteriorly, and the transverse colon and transverse colon mesentery inferiorly. The remainder of the abdominal cavity is the greater sac, and the two are connected via the foramen of Winslow. This is relevant to the clinical diagnosis of secondary peritonitis as perforation into the lesser sac, such as a perforated ulcer in the posterior gastric wall, may be temporarily contained in the lesser sac, preventing the patient from developing peritonitis. The peritoneum forms a semipermeable barrier through which water and solutes are passively exchanged. Regular circulation of peritoneal fluid is driven in part by the movement of the diaphragm.^{14 15} Bacteria and larger debris are cleared via stomata, lymphatic portals between mesothelial cells, which are concentrated on the diaphragmatic surface.¹⁶ The embryology, histology, and physiology of the peritoneum were reviewed recently by van Baal et al¹³