Peritoneum and Peritoneal Cavity
The peritoneum is a double layered membranous sac that houses many of the abdominal organs. One layer of the peritoneum known as the visceral peritoneum is attached to these organs, which are known as intra-peritenoeal organs. The other layer known as the parietal peritoneum lines the inner abdominopelvic wall. Between the visceral and parietal peritoneum is a potential space known as the peritoneal cavity. No organs lies in this space but a small amount of peritoneal fluid provides lubrication for the two layers to rub against each other. A series of peritoneal ligaments connect the intra-peritoneal organs to each other or to the abdominal wall.
Functions of the Peritoneum and Peritoneal Cavity
The peritoneum and peritoneal cavity are important parts of the human anatomy. These transparent and shiny membranes holds the abdominal organs in place within the abdominal cavity. It also reduces friction when these organs slide against each other and during movement as is the case with the highly active gastrointestinal tract. It allows these organs to move freely yet still maintain its position within the abdominal cavity.
Organs Outside the Peritoneal Cavity
Not all abdominopelvic organs are completely surrounded by peritoneum or housed within the peritoneal cavity. There are various terms attributed to these organs including extra-peritoneal, retroperitoneal and subperitoneal. For example, the kidneys are known as retroperitoneal organs because it lies behind the peritoneal cavity and only the parietal peritoneum covers its anterior (front) surface. The bladder is a subperitoneal organ because it lies below the peritoneal cavity and its superior (top) surface is the only part covered by the parietal peritoneum.
What is peritonitis?
Peritonitis is inflammation of the peritoneum. It often arises as a consequence of a bacterial infection but may also occur with chemical irritation that does not involve any infectious agents. The inflamed peritoneum may give rise to excessive peritoneal fluid secretion that accumulates within the peritoneal cavity – this is known as ascites. The fluid accumulation can be excessive to such a degree that a person becomes dehydrated.
This fluid may differ from the normal peritoneal fluid and can contain components like fibrin, pus, blood or cells which, when analyzed, can provide an indication to the cause of peritonitis. Depending on the cause, peritonitis may start off as a localized inflammation which can then spread to most of the peritoneum resulting in generalized peritonitis.
Types of Peritonitis
Most cases of peritonitis occur secondary to some other underlying disorder of the intra-peritoneal organs. For example when a gastrointestinal organ ruptures, the digestive enzymes may escape and irritate the peritoneum or the bacteria in the bowels may infect the peritoneum. However in some cases peritonitis occur on its own without any underlying disease that can directly irritate the peritoneum.
- Spontaneous peritonitis occurs when fluid builds up within the peritoneal cavity in diseases such as liver cirrhosis. This can predispose a person to infectious peritonitis as described below. Here the problem lies with balance between the amount of fluid being secreted into the cavity and the fluid being reabsorbed which normally maintains a minimal amount of peritoneal fluid.
- Sterile peritonitis is when there is peritoneal inflammation which is not due to an infection. It is often related to chemical irritation caused by digestive enzymes that are able to exit the alimentary tract.
- Infectious peritonitis, often bacterial or less frequently fungal, is inflammation of the peritoneum due to the invasion of pathogenic microorganisms typically following rupture or perforation of the abdominal organs. It may also occur spontaneously (spontaneous bacterial peritonitis) in blood-borne infections.
Causes of Peritonitis
Peritonitis may be due to a number of diverse conditions that can arise within the peritoneal cavity or occur secondary to underlying diseases that are not associated specifically with the peritoneum or intra-peritoneal organs.
- Rupture or perforation of an intra-peritoneal organ particularly the appendix (complication of appendicitis), stomach (stomach ulcer), gallbladder (complication of cholecystitis), small intestine (following intestinal ischemia) or colon (complication of diverticulitis).
- Trauma, complications following surgery or peritoneal dialysis may also lead to peritonitis even without a rupture of the intra-peritoneal organs. When the gastrointestinal organs are involved, chemical irritation may arise due to digestive enzymes or gut contents. This is rapidly followed by bacterial infection. In other cases, bleeding may cause peritoneal inflammation and bacteria may be introduced from the exterior directly into the peritoneal cavity.
- Pancreatitis, particularly acute hemorrhagic pancreatitis, where the pancreatic enzymes escape from the gland and irritate the peritoneum. Bacterial infection often follows.
- Blood is also an irritant to the peritoneum and may be seen with conditions such as endometriosis, ectopic pregnancy, sharp force trauma, ruptured aortic aneurysm.
- Fluid accumulation in the peritoneal cavity (ascites) can irritate the peritoneum thereby leading to spontaneous peritonitis. This is often associated with a secondary bacterial infection. It is most often seen with liver disease like cirrhosis which may be related to viral hepatitis or alcohol misuse. Congestive heart failure or Budd-Chiari syndrome are other conditions where spontaneous bacterial peritonitis may arise as a complication.
- Other causes may include :
- Foreign bodies introduced during surgery.
- Ruptured dermoid cysts.
Signs and Symptoms of Peritonitis
The most prominent symptoms that are usually severe includes :
- Abdominal pain and tenderness
- Nausea and vomiting
Other signs and symptoms of varying intensity include :
- Abdominal distension – enlarged abdomen
- Change in bowel habit – usually diarrhea but may include constipation
- Abdominal bloating – feeling of fullness
- Loss of appetite
- Thirst and signs of dehydration with severe ascites
- Oliguria or anuria – little or no urine output
- Fatigue and malaise