What are the anatomy, pathology, demographics, clinical presentation, assessment findings (early and late), EMS management, potential chronic medications, and complications of peritonitis relevant to a US national paramedic scope of practice?

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Last updated: September 8, 2026 • View editorial policy

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Peritonitis: Comprehensive Overview for US National Paramedic Scope of Practice

Anatomy and Pathophysiology

Normal Anatomy

The peritoneum is a serous membrane lining the abdominal cavity. It consists of two layers: the parietal peritoneum (lines the abdominal wall) and visceral peritoneum (covers the organs). The peritoneal cavity is a potential space containing a small amount of lubricating fluid (normally <50 mL). The abdominal cavity functions as a semi-rigid container with finite volume, subject to hydrostatic laws 1.

Pathological Changes

When peritonitis develops, the peritoneal lining becomes inflamed and infected. The inflammatory response causes:

  • Fluid accumulation: Massive fluid shifts from the vascular space into the peritoneal cavity (third-spacing), leading to hypovolemia and shock
  • Increased intra-abdominal pressure (IAP): As fluid and gas accumulate, IAP rises, causing visceral ischemia and multi-organ dysfunction 1
  • Bacterial proliferation: The peritoneal cavity becomes contaminated with bacteria, typically from gastrointestinal sources
  • Systemic inflammatory response: Release of toxic bio-mediators drives sepsis and multi-system organ failure (MSOF), even after source control 1
  • Peritoneal rigidity: The abdominal wall becomes rigid ("board-like") due to involuntary muscle guarding

Classification and Demographics

Types of Peritonitis

Primary Peritonitis 2, 3:

  • Spontaneous bacterial infection without GI tract perforation
  • Demographics: Cirrhotic patients with ascites, peritoneal dialysis patients, children
  • Prevalence: 1.5-3.5% in outpatients with cirrhosis, 10% in hospitalized cirrhotic patients 4
  • Usually single organism
  • Mortality: ~20% with early treatment 4

Secondary Peritonitis 2, 3:

  • Most common form paramedics encounter
  • Results from loss of GI tract integrity (perforation)
  • Demographics:
    • Appendicitis (most common cause, 34.2% of cases): Young adults, teens 3
    • Perforated peptic ulcer (11%): Middle-aged to elderly, NSAID users, H. pylori infection 3
    • Diverticulitis (5.2%): Elderly patients (>50 years) 3
    • Cholecystitis (18.5%): Middle-aged to elderly, females, obesity 3
    • Post-operative: Recent abdominal surgery patients 2
    • Trauma: Young males, penetrating or blunt abdominal trauma 3
  • Overall mortality: 6% (rises to 35% with severe sepsis) 5

Tertiary Peritonitis 2:

  • Recurrent infection >48 hours after initial surgical treatment
  • Demographics: Critically ill, immunocompromised, ICU patients
  • Associated with multidrug-resistant organisms
  • Mortality: 75.9% to near 100% 1

Why These Demographics?

  • Cirrhotic patients: Ascitic fluid provides bacterial growth medium; impaired immune function 4
  • Elderly: Decreased immune response, multiple comorbidities, atypical presentations 2
  • Post-surgical patients: Anastomotic dehiscence, contamination during surgery 3
  • Immunocompromised: Chemotherapy, HIV, diabetes—impaired ability to contain infection 2

Clinical Presentation: Signs and Symptoms

Early Presentation (What Paramedics See First)

Localized Peritonitis 2, 6:

  • Sharp, localized abdominal pain (patient can point with one finger)
  • Pain worsens with movement, coughing, or palpation
  • Voluntary guarding over affected area
  • Nausea and vomiting
  • Low-grade fever (100-101°F)
  • Tachycardia (HR 90-110)
  • Patient lies still, knees drawn up to reduce pain
  • Rebound tenderness (pain when pressure released)

Specific Patterns:

  • Right lower quadrant: Appendicitis
  • Right upper quadrant: Cholecystitis
  • Left lower quadrant: Diverticulitis 6
  • Epigastric: Perforated ulcer

Late Presentation (Diffuse Peritonitis/Sepsis)

Critical Signs 1, 2:

  • Diffuse abdominal pain (entire abdomen involved)
  • Board-like rigidity (involuntary guarding—peritonism)
  • Absent bowel sounds (paralytic ileus)
  • High fever (>101°F) or hypothermia (<96°F)
  • Severe tachycardia (HR >120)
  • Hypotension (SBP <90 mmHg)—septic shock
  • Altered mental status (confusion, lethargy)
  • Tachypnea (RR >22)
  • Mottled, cool skin (poor perfusion)
  • Decreased urine output
  • Abdominal distension
  • Patient appears toxic, severely ill

Paramedic Assessment Findings

Early Assessment Findings

Vital Signs:

  • Temperature: 100-102°F
  • Heart rate: 90-110 bpm
  • Blood pressure: Normal to slightly elevated (compensated)
  • Respiratory rate: 18-22 breaths/min
  • SpO2: Normal (>94%)

Physical Exam:

  • Localized tenderness with voluntary guarding
  • Positive rebound tenderness
  • Pain with percussion
  • Patient prefers to lie still
  • Normal skin color and perfusion
  • Alert and oriented

SAMPLE History Red Flags:

  • Recent abdominal surgery
  • History of ulcers, diverticulitis, or inflammatory bowel disease
  • Cirrhosis with ascites
  • Peritoneal dialysis
  • Recent trauma
  • NSAID or steroid use

Late Assessment Findings (Critical)

Vital Signs:

  • Temperature: >102°F or <96°F
  • Heart rate: >120 bpm (weak, thready pulse)
  • Blood pressure: <90 mmHg systolic (septic shock)
  • Respiratory rate: >24 breaths/min (compensatory)
  • SpO2: May be decreased (<90%)
  • Altered mental status (GCS <15)

Physical Exam:

  • Board-like abdominal rigidity (involuntary)
  • Diffuse tenderness entire abdomen
  • Absent bowel sounds
  • Abdominal distension
  • Cool, mottled, diaphoretic skin
  • Delayed capillary refill (>2 seconds)
  • Signs of shock (weak pulses, altered consciousness)

EMS Management and Treatment

Initial Scene Assessment and Primary Survey

Scene Safety: Standard precautions, consider infectious risk

Primary Assessment (ABCDE):

  1. Airway: Assess patency; high risk of aspiration from vomiting
  2. Breathing: Assess rate, depth, work of breathing; shallow breathing common due to abdominal pain
  3. Circulation: Assess pulses, skin signs, capillary refill
  4. Disability: Mental status (AVPU or GCS)
  5. Exposure: Expose abdomen for assessment

Critical Decision Point: Transport Priority

IMMEDIATE TRANSPORT (Load-and-Go) 1, 2, 3:

  • Diffuse peritonitis with board-like rigidity
  • Signs of septic shock (hypotension, altered mental status, mottled skin)
  • Severe tachycardia (>120) with hypotension
  • Altered mental status
  • Recent abdominal surgery with acute abdomen
  • Known or suspected GI perforation

Stable Transport (Treat and Transport):

  • Localized peritonitis
  • Stable vital signs
  • Alert and oriented
  • No signs of shock

Treatment Protocol (Start to Facility Transfer)

For All Patients:

  1. Position: Position of comfort (usually supine with knees flexed)
  2. Oxygen: Titrate to SpO2 >94%
  3. IV Access: Two large-bore IVs (18-gauge or larger) if signs of shock
  4. Cardiac Monitor: Continuous monitoring
  5. Nothing by Mouth: NPO status
  6. Pain Management:
    • Fentanyl 1 mcg/kg IV (50-100 mcg) for severe pain
    • Morphine 0.1 mg/kg IV (alternative)
    • Do NOT withhold analgesia—outdated concern about masking surgical findings
  7. Antiemetics: Ondansetron 4 mg IV for nausea/vomiting

For Patients in Shock 1, 5:

  1. Aggressive Fluid Resuscitation:

    • Normal saline or Lactated Ringer's bolus: 20 mL/kg (1-2 liters for adults)
    • Reassess after each bolus
    • Target SBP >90 mmHg
    • Caution: Fluid resuscitation increases intra-abdominal pressure but is necessary for perfusion 1

  2. Vasopressors (if available in scope):

    • If hypotension persists after 2-3 liters fluid
    • Norepinephrine infusion per protocol

  3. Airway Management:

    • Consider early intubation if altered mental status or respiratory failure
    • Rapid sequence intubation if needed

  4. Rapid Transport: Notify receiving facility early—surgical emergency

Transport Considerations

Destination Selection:

  • Trauma center or facility with 24/7 surgical capability
  • Avoid urgent care or facilities without surgical services
  • Diffuse peritonitis requires immediate surgical exploration 2, 3

En Route:

  • Continuous vital sign monitoring every 5 minutes
  • Reassess abdomen for worsening rigidity or distension
  • Document fluid administration and response
  • Maintain NPO status
  • Keep patient warm (hypothermia worsens outcomes)

Hospital Notification:

  • Age and chief complaint
  • Vital signs and trends
  • Physical findings (localized vs. diffuse, rigidity)
  • Pertinent history (recent surgery, cirrhosis, dialysis)
  • Treatments provided and response
  • ETA

Chronic Condition Considerations

Peritonitis is NOT a chronic condition—it is an acute surgical emergency. However, patients may have chronic conditions that predispose them to peritonitis:

Cirrhotic Patients on Chronic Medications 4

Diuretics (Spironolactone, Furosemide):

  • Purpose: Manage ascites (fluid accumulation)
  • Relevance: Ascitic fluid is medium for spontaneous bacterial peritonitis
  • Paramedic Consideration: May be volume depleted; assess for dehydration

Beta-blockers (Propranolol, Nadolol):

  • Purpose: Prevent variceal bleeding
  • Relevance: May mask tachycardia; cannot rely on heart rate for shock assessment
  • Paramedic Consideration: Hypotension may occur without compensatory tachycardia

Lactulose:

  • Purpose: Prevent hepatic encephalopathy
  • Relevance: Causes diarrhea; may complicate assessment
  • Paramedic Consideration: Altered mental status may be from encephalopathy or sepsis

Peritoneal Dialysis Patients 7, 8

Chronic Peritoneal Dialysis:

  • Relevance: Catheter provides direct route for infection
  • Medications: May be on prophylactic antibiotics
  • Paramedic Consideration: Cloudy dialysate fluid = peritonitis until proven otherwise

Post-Surgical Patients

Antibiotics: May be on post-operative prophylaxis Anticoagulants: Increased bleeding risk Immunosuppressants (transplant patients): Higher infection risk, atypical presentations

Complications of Untreated Peritonitis

Early Complications (Hours to Days) 1, 5, 9

Hypovolemic Shock:

  • Mechanism: Massive third-spacing of fluid into peritoneal cavity
  • Result: Decreased circulating volume, hypotension, organ hypoperfusion
  • Mortality: Increases significantly without fluid resuscitation

Septic Shock 2, 5:

  • Mechanism: Bacterial toxins and inflammatory mediators cause vasodilation and capillary leak
  • Result: Distributive shock, hypotension despite fluid resuscitation
  • Mortality: 67.8% with septic shock 2

Intra-Abdominal Hypertension (IAH) 1:

  • Mechanism: Fluid and gas accumulation increases intra-abdominal pressure
  • Result: Visceral ischemia, decreased venous return, respiratory compromise
  • Progression: Can lead to abdominal compartment syndrome

Intermediate Complications (Days) 1, 9

Respiratory Failure:

  • Mechanism: Elevated diaphragm from increased IAP, pulmonary edema from fluid shifts
  • Result: ARDS, need for mechanical ventilation

Acute Kidney Injury:

  • Mechanism: Hypoperfusion, direct compression from IAH, sepsis
  • Result: Oliguria, anuria, need for dialysis

Paralytic Ileus 9:

  • Mechanism: Inflammatory mediators halt bowel motility
  • Result: Abdominal distension, vomiting, inability to tolerate oral intake
  • Incidence: 6.4% of peritonitis patients 9

Abscess Formation:

  • Mechanism: Localized pockets of infection wall off
  • Result: Persistent fever, need for drainage procedures

Late Complications (Weeks) 1, 2, 9

Multi-System Organ Failure (MSOF) 1:

  • Mechanism: Toxic bio-mediators drive systemic inflammation
  • Result: Sequential failure of lungs, kidneys, liver, heart
  • Mortality: Near 100% with abdominal compartment syndrome 1

Septicemia 9:

  • Mechanism: Bacteria enter bloodstream
  • Result: Systemic infection, endocarditis, metastatic abscesses
  • Incidence: 11.3% of peritonitis patients 9

Tertiary Peritonitis 2:

  • Mechanism: Recurrent infection after initial treatment
  • Result: Prolonged ICU stay, multiple surgeries, multidrug-resistant organisms
  • Mortality: 75.9% to near 100% 1

Adhesions and Bowel Obstruction:

  • Mechanism: Chronic inflammation causes scar tissue formation
  • Result: Recurrent bowel obstructions requiring surgery

Death 5, 9:

  • Overall mortality: 6% (uncomplicated)
  • With severe sepsis: 35%
  • With septic shock: 67.8% 2
  • Hospital mortality: 3.2% overall 9

Why Complications Develop

Time-Dependent Progression:

  • 0-6 hours: Localized inflammation, compensated shock
  • 6-24 hours: Diffuse peritonitis, decompensated shock, organ dysfunction begins
  • 24-48 hours: MSOF, ARDS, acute kidney injury
  • >48 hours: Tertiary peritonitis, death

Key Point for Paramedics: Early recognition and rapid transport to surgical facility is critical. Delayed source control (surgical intervention) is the primary driver of mortality 3. Every hour of delay increases risk of progression from localized to diffuse peritonitis and from sepsis to septic shock.

References

7
Research

Clinical practice guideline for the prevention and management of peritoneal dialysis associated infections in children: 2024 update.

Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis, 2024

8
Research

Comparative simulation of intraperitoneal aminoglycoside regimens for patients with peritonitis on automated peritoneal dialysis.

Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis, 2024

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