Peritonitis is inflammation of the peritoneum, the serous membrane lining the abdominal cavity and covering the organs. It is usually caused by infection and can quickly lead to sepsis and septic shock.

Types

Pathophysiology

• Bacteria and irritants trigger inflammation: capillaries leak, and large amounts of fluid shift into the peritoneal cavity and bowel wall (third spacing) → hypovolemia
• Bowel motility stops (paralytic ileus) → distension, vomiting, further fluid loss
• The body tries to wall off the infection (fibrin, omentum), which can form abscesses and later adhesions
• Bacterial toxins cause systemic inflammation → sepsis, organ dysfunction (AKI, ARDS), and septic shock

Classic findings (secondary peritonitis)

• Severe abdominal pain, often starting at the source and becoming diffuse; worse with movement, coughing, or jarring
• Rigid, board-like abdomen, involuntary guarding, rebound tenderness
• Client lies very still with knees flexed
• Distension, diminished or absent bowel sounds (ileus), nausea, vomiting, anorexia
• Fever, chills, tachycardia, tachypnea (shallow breathing to limit pain)
• Signs of hypovolemia and sepsis: hypotension, oliguria, altered mental status, cool or mottled skin

Atypical presentations — older adults, clients taking corticosteroids or immunosuppressants, and those with spinal cord injury may have little pain or rigidity. SBP may cause only fever, mild abdominal tenderness, worsening encephalopathy, or rising creatinine.

PD-associated peritonitis — classic triad: abdominal pain, fever, and cloudy dialysis effluent. Cloudy effluent is peritonitis until proven otherwise.

Sepsis care (Surviving Sepsis Campaign 2021, updated 2026)

• Broad-spectrum IV antibiotics as soon as possible — within 1 hour when septic shock or sepsis is likely
• IV crystalloid about 30 mL/kg for sepsis-induced hypoperfusion or shock, reassessing after each bolus; use caution in cirrhosis, heart failure, and kidney failure. Lactate guides resuscitation but a raised lactate alone should not trigger more fluid
• Norepinephrine first-line vasopressor, initial target mean arterial pressure 65 mmHg; the 2026 update suggests a target of 60–65 mmHg for clients aged 65 or older, and vasopressors may be started through a peripheral IV (and alongside fluids) rather than delayed until central access
• Oxygen, and ventilation support as needed

Source control — the key step for secondary peritonitis

• Surgery: laparotomy or laparoscopy to close perforations, remove the source (e.g., appendix, perforated colon segment), and irrigate (lavage) the peritoneal cavity; temporary stoma may be created; the abdomen is sometimes left open for planned re-look
• Percutaneous drainage of localized abscesses under CT guidance

Supportive — NPO, NG decompression for ileus and vomiting, fluids and electrolytes, analgesia (opioids — do not withhold pain relief), nutrition support (enteral when possible), VTE prophylaxis.

Antibiotics — examples and safety

• Secondary peritonitis: coverage of gram-negative and anaerobic organisms (e.g., piperacillin–tazobactam, a carbapenem, or a cephalosporin plus metronidazole)
  • Piperacillin–tazobactam: penicillin allergy; with vancomycin, higher AKI risk
  • Carbapenems: seizure risk at high levels; meropenem lowers valproate levels (seizure risk)
  • Aminoglycosides: nephrotoxicity and ototoxicity — monitor levels and kidney function; avoid when possible in cirrhosis
  • Vancomycin (if MRSA risk): monitor levels (trough or AUC) and creatinine; infuse slowly to prevent infusion reaction (flushing, rash)
  • Ceftriaxone: allergy, biliary sludge, no co-infusion with calcium solutions in neonates; metronidazole: see Diverticular Disease
• SBP: IV third-generation cephalosporin (cefotaxime or ceftriaxone) plus IV albumin — 1.5 g/kg on day 1 and 1 g/kg on day 3, especially when creatinine is above 1 mg/dL (88 µmol/L), BUN above 30 mg/dL (urea 10.7 mmol/L), or bilirubin above 4 mg/dL (68 µmol/L)
• PD peritonitis: intraperitoneal (IP) antibiotics are preferred unless the client is septic (then IV); often vancomycin or a first-generation cephalosporin plus gram-negative coverage; catheter removal for refractory or fungal peritonitis

Listed in priority order.

1. Airway and breathing — semi-Fowler's position (eases breathing, helps localize fluid in the pelvis); oxygen; monitor respiratory rate, SpO₂, lung sounds
2. Circulation and sepsis recognition
   • Frequent vital signs, mental status, capillary refill, skin
   • Strict intake and output, hourly urine output (at least 0.5 mL/kg/h) via catheter
   • Establish IV access; give fluids, antibiotics, and vasopressors promptly as ordered; draw cultures before antibiotics without delaying them
3. Serial abdominal assessment — pain (character, location, intensity), rigidity, distension, girth, bowel sounds; report sudden worsening
4. Pain management — give analgesics as ordered and reassess regularly; document pain pattern (it reflects disease course). Do not apply heat to the abdomen
5. GI decompression — NPO; NG tube patency and output; frequent oral care; no oral intake, laxatives, or enemas during ileus
6. Temperature — monitor the fever pattern (response to treatment); give antipyretics per order rather than routinely suppressing fever
7. Wound, drain, and open-abdomen care — sterile technique, drainage amount and character, skin protection
8. Infection control — standard precautions; peritonitis itself does not require isolation unless a specific organism (e.g., MRSA, C. difficile) calls for transmission-based precautions
9. PD clients — save the cloudy effluent bag for testing; administer IP antibiotics with strict aseptic technique

Peritoneal dialysis clients

• Hand hygiene and mask during exchanges; aseptic connection technique; daily exit-site care
• Report cloudy effluent, abdominal pain, or fever immediately and bring the cloudy bag to the unit
• Retraining in exchange technique after an episode; follow instructions for home IP antibiotics
• Report accidental contamination (touching the connector) — prophylactic antibiotics may be given

After surgery

• Wound care, signs of infection, activity limits, splinting the incision when coughing
• Stoma care if created
• Report fever, increasing abdominal pain, vomiting, or wound drainage

Cirrhosis with ascites — take SBP prophylaxis antibiotics as prescribed; report fever, abdominal pain, or confusion.

Recovery — appetite and energy return slowly after severe peritonitis; eat small, protein-rich meals, walk a little more each day, and keep follow-up appointments. Late bowel obstruction from adhesions can occur months or years later: report cramping pain, vomiting, and inability to pass gas.

• Classic signs: rigid board-like abdomen, rebound tenderness, fever, tachycardia, client lies still with knees flexed
• Most common type: secondary (perforation — appendix, ulcer, diverticulum)
• Free air on upright X-ray = perforation
• SBP: cirrhosis with ascites; ascitic PMN ≥ 250 cells/mm³
• PD peritonitis: pain, fever, cloudy effluent; effluent WBC more than 100/µL with more than 50% neutrophils; intraperitoneal antibiotics preferred
• Sepsis care: antibiotics within 1 hour, about 30 mL/kg crystalloid with reassessment, norepinephrine for MAP 65 mmHg (60–65 in clients 65 or older)
• Source control (surgery or drainage) is essential in secondary peritonitis
• Priority nursing data: vital signs, I&O and urine output, serial pain and abdominal assessment
• NPO + NG decompression for ileus; no laxatives or enemas
• Standard precautions — no special isolation for peritonitis itself
• Aminoglycosides and vancomycin: monitor levels and kidney function