The peritoneal cavity is a potential space between the  parietal peritoneum (the peritoneum that surrounds the abdominal wall) and visceral peritoneum (the peritoneum that surrounds the internal organs). The parietal and visceral peritonea are layers of the peritoneum named depending on their function/location. It is one of the spaces derived from the coelomic cavity of the embryo, the others being the pleural cavities around the lungs and the pericardial cavity around the heart. It is the largest serosal sac, and the largest fluid-filled cavity, in the body and secretes approximately 50 ml of fluid per day. This fluid acts as a lubricant and has anti-inflammatory properties. The peritoneal cavity is divided into two compartments – one above, and one below the transverse colon. Compartments
The peritoneal cavity is divided by the transverse colon (and its mesocolon) into an upper supracolic compartment, and a lower infracolic compartment. The liver, spleen, stomach, and lesser omentum are contained within the supracolic compartment. The small intestine surrounded by the ascending, transverse, and descending colon, and the paracolic gutters are contained within the infracolic compartment. Clinical significance
The peritoneal cavity is a common injection site, used in intraperitoneal injection. An increase in the capillary pressure in the abdominal viscera can cause fluid to leave the interstitial space and enter the peritoneal cavity, a condition called ascites.
In other cases it is inherited from one affected parent.Loeys–Dietz syndrome was identified and characterized by pediatric geneticists Bart Loeys and Harry "Hal" Dietz at Johns Hopkins University in 2005. Signs and symptoms
There is considerable variability in the phenotype of Loeys–Dietz syndrome, from mild features to severe systemic abnormalities. The primary manifestations of Loeys–Dietz syndrome are arterial tortuosity (winding course of blood vessels), widely spaced eyes (hypertelorism), wide or split uvula, and aneurysms at the aortic root. Other features may include cleft palate and a blue/gray appearance of the white of the eyes. Cardiac defects and club foot may be noted at birth.There is overlap in the manifestations of Loeys–Dietz and Marfan syndromes, including increased risk of ascending aortic aneurysm and aortic dissection, abnormally long limbs and fingers, and dural ectasia (a gradual stretching and weakening of the dura mater that can cause abdominal and leg pain).