Peritonitis: Causes, Pathophysiology, Clinical Features, Diagnosis, Management, and Prevention
Introduction
Peritonitis is a serious and potentially life-threatening inflammatory condition of the peritoneum—the thin, serous membrane lining the abdominal cavity and covering most of the abdominal organs. The peritoneum functions as a protective layer, facilitating minimal friction during the movement of abdominal organs, while also serving as a semi-permeable membrane involved in fluid exchange and immune defense. When this membrane becomes inflamed due to infection, chemical irritation, or physical injury, a systemic inflammatory response can ensue, often rapidly progressing to sepsis, shock, and multi-organ failure if not promptly treated.
Peritonitis is a medical emergency requiring early recognition and urgent intervention. The incidence of peritonitis varies globally depending on the underlying cause, regional access to healthcare, prevalence of abdominal infections, and the rate of chronic conditions such as liver cirrhosis and kidney failure. Despite advancements in diagnosis and treatment, peritonitis remains associated with significant morbidity and mortality.
This article provides a comprehensive overview of peritonitis including its anatomy, types, causes, mechanisms, clinical presentation, diagnostic evaluation, management strategies, complications, and preventive measures.
Anatomy and Physiology of the Peritoneum
The peritoneum is a large, thin, and moist serous membrane consisting of two layers:
- Parietal Peritoneum – lines the internal surface of the abdominal wall.
- Visceral Peritoneum – covers the abdominal organs (viscera).
Between these two layers is the peritoneal cavity, containing a small amount of lubricating serous fluid that enables smooth movement of abdominal organs. The peritoneum has a rich supply of blood vessels and lymphatics and plays an active role in immune defense by producing macrophages and cytokines.
Functions of the Peritoneum
- Provides protective immunologic barrier
- Facilitates frictionless movement of abdominal organs
- Serves as a pathway for blood and lymphatic circulation
- Assists in fluid and solute transport
Any disruption to this delicate environment leads to inflammation—peritonitis.
Types of Peritonitis
Peritonitis can be broadly categorized into three major types:
1. Primary (Spontaneous) Peritonitis
This occurs without an evident source of infection within the abdomen. It is most commonly seen in patients with:
- Cirrhosis with ascites
- Nephrotic syndrome
- Peritoneal dialysis
The infection typically results from hematogenous spread of bacteria or translocation from the gut.
2. Secondary Peritonitis
This is the most common form, resulting from an intra-abdominal pathology that allows infectious material (bacteria, bile, enzymes, or gastric acid) to enter the peritoneal cavity.
Major causes include:
- Perforated peptic ulcer
- Appendiceal rupture
- Diverticulitis with perforation
- Perforated bowel from trauma
- Pancreatitis with necrosis
- Post-operative infections
3. Tertiary Peritonitis
This refers to persistent or recurrent peritonitis after adequate initial treatment. It occurs mostly in:
- Immunocompromised patients
- Patients with multiple organ failure
- Long ICU stays
Etiology (Causes)
Bacterial Causes
- Gram-negative organisms (e.g., E. coli, Klebsiella)
- Gram-positive organisms (e.g., Streptococcus, Enterococcus)
- Anaerobes (e.g., Bacteroides)
- Less commonly Mycobacterium tuberculosis
Chemical or Sterile Causes
- Pancreatic enzymes leading to chemical peritonitis
- Spillage of gastric/intestinal contents
- Bile leakage after gallbladder surgery or trauma
Fungal Causes
Seen primarily in immunocompromised individuals and critically ill patients.
Pathophysiology
When the peritoneum is exposed to infectious or chemical irritants, an acute inflammatory cascade is triggered:
- Microorganisms or irritants enter the peritoneal cavity.
- The peritoneum responds by producing pro-inflammatory cytokines.
- Exudation of fluid, proteins, and immune cells occurs.
- The peritoneal cavity fills with pus or inflammatory fluid, causing distension.
- The inflammatory response may become systemic, leading to sepsis and septic shock.
If untreated, peritonitis can rapidly progress to:
- Hypovolemia due to fluid sequestration
- Multi-organ dysfunction
- Death
Clinical Features
Patients with peritonitis typically present with:
Symptoms
- Severe abdominal pain – often sudden in onset
- Pain worsens with movement or coughing
- Nausea and vomiting
- Loss of appetite
- Fever and chills
- Abdominal distension
- Inability to pass stools or gas (ileus)
Signs on Physical Examination
- Tenderness over the affected area or generalized
- Guarding (voluntary muscle tension)
- Rigidity (involuntary reflex muscle contraction)
- Rebound tenderness
- Absent or reduced bowel sounds
- Tachycardia
- Hypotension in severe cases
A classic sign is the patient lying still because any movement worsens pain.
Diagnosis
1. Blood Tests
- Complete blood count: Leukocytosis
- Elevated CRP and ESR
- Blood cultures if sepsis is suspected
- Serum electrolytes for dehydration and acidosis
2. Imaging
- Ultrasound: Detects ascites, abscess, perforations.
- X-ray abdomen: Free air under diaphragm indicates perforation.
- CT Scan: Most sensitive; identifies source, extent, abscesses.
3. Diagnostic Paracentesis
Especially important in ascites or suspected spontaneous bacterial peritonitis (SBP).
- Ascitic fluid analysis includes:
- Cell count (>250 polymorphonuclear leukocytes suggests SBP)
- Gram stain and culture
- Protein and LDH levels
Management
Peritonitis is a medical emergency requiring rapid and aggressive treatment.
1. Immediate Supportive Care
- IV fluid resuscitation
- Oxygen supplementation
- Electrolyte correction
- Pain control
- Monitoring for shock
2. Antibiotic Therapy
Empirical broad-spectrum antibiotics are started immediately.
Common regimens:
- Third-generation cephalosporin (e.g., cefotaxime/ceftriaxone) for SBP
- Piperacillin-tazobactam, carbapenems, or cephalosporin + metronidazole for secondary peritonitis
Therapy is adjusted based on culture results.
3. Surgical Management
Indicated for secondary peritonitis due to perforation or abscess. Procedures may include:
- Appendectomy
- Repair of perforated ulcer
- Drainage of abscess
- Resection of necrotic bowel
- Laparotomy or laparoscopy for abdominal lavage
4. Peritoneal Dialysis-Associated Peritonitis Treatment
- Intra-peritoneal antibiotics
- Temporary shift to hemodialysis if necessary
Complications
If not treated urgently, peritonitis may lead to:
- Sepsis and septic shock
- Multi-organ failure
- Liver and kidney failure
- Adhesions → leading to intestinal obstruction
- Intra-abdominal abscess formation
- Chronic pain and reduced quality of life
Mortality rate remains high, especially in elderly or patients with comorbidities.
Prognosis
The prognosis depends on:
- The underlying cause
- Age and comorbidities
- Time of intervention
Early diagnosis and rapid management significantly improve outcomes.
Prevention
Primary Prevention
- Educating patients with cirrhosis about SBP risks
- Avoiding unnecessary invasive abdominal procedures
Secondary Prevention
- Long-term antibiotic prophylaxis in high-risk SBP patients
- Strict aseptic technique in peritoneal dialysis
Public Health and Lifestyle Measures
- Timely treatment of gastrointestinal illnesses
- Safe surgical practices
- Controlled alcohol consumption to reduce cirrhosis risk
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Conclusion
Peritonitis is a critical, rapidly developing inflammatory condition requiring urgent recognition and intervention. Understanding its causes, pathophysiology, and clinical presentation is essential for timely diagnosis and management. Treatment typically involves a combination of resuscitative measures, antibiotic therapy, and surgical intervention when appropriate. While advances in modern medicine have improved outcomes, the mortality rate remains significant, particularly when diagnosis is delayed.
Preventive strategies, especially for individuals with chronic conditions like cirrhosis or those undergoing peritoneal dialysis, are crucial in reducing the incidence of peritonitis. Ultimately, rapid response, appropriate management, and continuous monitoring are key to improving survival rates and patient quality of life.
