Peritoneal inflammation, medically known as peritonitis, is a severe inflammatory response affecting the membrane that lines the inner wall of the abdomen and covers the abdominal organs. It is frequently caused by a bacterial infection or the introduction of chemical irritants into the abdominal cavity. Peritonitis is a serious medical event that can rapidly lead to life-threatening complications, including sepsis and systemic organ failure. Immediate medical intervention is necessary because a delay in diagnosis and treatment significantly increases the risk of mortality.
The Peritoneum and Inflammation
The peritoneum is a thin, two-layered serous membrane that acts as a protective lining within the abdominopelvic cavity. The inner layer (visceral peritoneum) envelops the internal organs, while the outer layer (parietal peritoneum) adheres to the abdominal wall. These layers enclose the peritoneal cavity, which normally contains a small amount of lubricating fluid allowing organs to glide smoothly during movement.
The peritoneum also plays a significant role in immunity and fluid absorption, serving as a first line of defense against infection. Peritonitis begins when this normally sterile cavity is contaminated by bacteria or irritating substances. This contamination triggers a massive inflammatory cascade, leading to the dilation of blood vessels and increased permeability. The body’s response results in the rapid accumulation of inflammatory fluid and fibrin, which often leads to diffuse inflammation and systemic illness.
Categorizing the Causes
The source of contamination dictates the classification of peritoneal inflammation, which is divided into three major categories.
Secondary Peritonitis
Secondary peritonitis is the most common form, arising from a breach in the integrity of a hollow abdominal organ. This occurs when bacteria-rich gastrointestinal contents spill into the peritoneal cavity. Common causes include a ruptured appendix, a perforated peptic ulcer, perforations due to diverticulitis, trauma, or complications following abdominal surgery.
Primary Peritonitis
Primary peritonitis, also called spontaneous bacterial peritonitis (SBP), occurs without an obvious source of contamination or perforation within the abdomen. This form is often seen in patients with chronic liver disease and ascites (fluid accumulation in the peritoneal cavity). The mechanism involves the translocation of bacteria from the gut wall or bloodstream into the ascitic fluid. SBP is typically caused by a single type of bacteria, unlike secondary peritonitis, which is often polymicrobial.
Tertiary and Chemical Peritonitis
Tertiary peritonitis describes a persistent or recurrent infection that develops after initial treatment for secondary peritonitis. This condition occurs in critically ill or immunocompromised patients whose immune response fails to clear the initial infection. Tertiary peritonitis is characterized by a low-grade infection, often caused by less virulent organisms like fungi or multi-drug resistant bacteria. Sterile or chemical peritonitis occurs when non-bacterial fluids, such as bile or digestive enzymes, leak into the cavity and cause intense irritation.
Identifying the Symptoms
Peritonitis typically presents with severe, sudden abdominal pain that is frequently diffuse across the abdomen. The pain tends to worsen significantly with movement, coughing, or deep breathing. A specific sign elicited during physical examination is rebound tenderness, where pain increases when pressure is quickly released from the abdomen.
The abdominal muscles often involuntarily contract, resulting in abdominal rigidity or a “board-like” abdomen. Systemic symptoms usually follow the localized pain, including a high fever, chills, and signs of a systemic inflammatory response, such as tachycardia (a rapid heart rate). Nausea and vomiting are common, as the inflammation often leads to an ileus, which is a temporary paralysis of intestinal movement.
Diagnosis and Treatment Protocols
Diagnosing peritoneal inflammation begins with a detailed physical examination, focusing on the characteristic signs of tenderness and rigidity. Blood tests are essential, typically showing an elevated white blood cell count, indicating a strong immune response to infection. Blood cultures may also be drawn to identify the specific pathogen responsible if the infection has entered the bloodstream.
Imaging studies are crucial for confirming the diagnosis and identifying the source of contamination. A computed tomography (CT) scan is the preferred method, as it can reveal free fluid or air in the peritoneal cavity, which strongly suggests a perforation. In cases of ascites, a procedure called paracentesis is performed, where a needle is used to withdraw a sample of the peritoneal fluid for laboratory analysis. The presence of a high number of white blood cells, specifically neutrophils, in the fluid confirms the diagnosis of peritonitis.
Treatment for peritonitis is a two-pronged strategy that requires both medical and, frequently, surgical intervention. Medical management involves the immediate administration of broad-spectrum intravenous antibiotics to cover the likely mixture of organisms, especially in secondary peritonitis. The patient’s fluid and electrolyte balance must be stabilized, as the inflammatory process causes significant fluid shifts.
Surgical intervention is mandatory for nearly all cases of secondary peritonitis to control the source of contamination. This procedure, which may be a laparotomy or laparoscopy, involves identifying and repairing the site of the breach, such as closing a perforation or removing an infected organ like the appendix. Following source control, the abdominal cavity is thoroughly washed out, a process known as peritoneal lavage, to remove pus, bacteria, and irritating contaminants.