The peritoneal cavity is the potential space between the visceral peritoneum (covering the abdominal organs) and the parietal peritoneum (lining the abdominal wall and diaphragm), normally containing only a thin film of peritoneal fluid (50-100 mL). It is divided into supra- and infra-mesenteric compartments by the transverse mesocolon, and the greater sac (main cavity) communicates with the lesser sac (omental bursa) through the epiploic foramen of Winslow.
Free fluid in the peritoneal cavity (ascites from cirrhosis, malignant ascites, haemorrhage from trauma, or hollow viscus perforation with peritoneal contamination) is detected by FAST ultrasound in the dependent Morison's pouch, the splenorenal recess, and the pelvis. Diagnostic peritoneal lavage and diagnostic laparoscopy assess peritoneal contamination in trauma and suspected perforation. Peritoneal carcinomatosis from gastric, colorectal, and ovarian cancer distributes tumour implants throughout the peritoneal cavity requiring cytoreductive surgery and heated intraperitoneal chemotherapy (HIPEC). Spontaneous bacterial peritonitis infects the ascites fluid in cirrhotic patients.
Gastroduodenal perforation from peptic ulcer disease or colonic perforation from diverticulitis contaminates the peritoneal cavity with gastrointestinal contents, producing generalised peritonitis with board-like rigidity and surgical emphysema; emergency laparotomy performs source control by primary closure, resection, or ostomy formation combined with peritoneal lavage.
