Peritonitis

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Peritonitis - Belly on Fire

  • Inflammation of the peritoneum, the silk-like membrane lining the abdominal wall.

  • Types

    • Spontaneous Bacterial Peritonitis (SBP): Infection of ascitic fluid, usually from cirrhosis. No evident source.
      • Dx: Ascitic fluid PMN > 250 cells/mm³.
      • Common bugs: E. coli, Klebsiella, Strep pneumo.
    • Secondary Peritonitis: Due to perforation of a viscus (e.g., appendix, ulcer).
      • Polymicrobial infection is common.
  • Clinical Features

    • Fever, abdominal pain, guarding, rebound tenderness.
    • Classic sign: Board-like rigidity.

High-Yield: In a patient with cirrhosis, ascites, and fever, a paracentesis showing a neutrophil count (PMN) of > 250/mm³ is diagnostic for SBP.

Guarding and Rebound Tenderness in Peritonitis

SBP - Cirrhosis's Sneaky Friend

Paracentesis procedure for peritonitis diagnosis

  • Definition: Bacterial infection of ascitic fluid without an evident intra-abdominal source, common in advanced cirrhosis.
  • Etiology: Primarily monomicrobial. Gram-negative bacilli are most frequent, especially E. coli (~70%), Klebsiella, and Streptococcus species.
  • Clinical: Can be subtle. Look for fever, abdominal pain, and altered mental status (worsening hepatic encephalopathy).
  • Diagnosis: Requires paracentesis. Key finding is an ascitic fluid absolute neutrophil count (PMN) $≥ \textbf{250}/mm^3$.
  • Management:
    • Empiric antibiotics (e.g., 3rd-gen cephalosporin like cefotaxime).
    • IV albumin infusion.

High-Yield: Initiate treatment based on a PMN count $≥ \textbf{250}/mm^3$ alone. Do not wait for culture results, as they have low sensitivity and delay can be fatal.

Secondary Peritonitis - The Great Escape

  • Pathophysiology: Breach of GI/GU tract integrity → spillage of polymicrobial gut flora into the normally sterile peritoneal cavity.
  • Common Causes: Perforated peptic ulcer, acute appendicitis, diverticulitis, trauma, or iatrogenic injury.
  • Microbiology: Mixed aerobes (E. coli, Klebsiella) and anaerobes (Bacteroides fragilis).
  • Diagnosis: Clinical signs of an acute abdomen (rebound tenderness, guarding). Upright CXR or CT scan confirms pneumoperitoneum (free air).

Bacteroides fragilis is the most common anaerobe isolated, mandating antibiotic coverage for anaerobes.

Upright CXR: Free subdiaphragmatic air (pneumoperitoneum)

Dx & Tx - Find It, Fix It

  • Find It (Diagnosis):

    • Labs: CBC (↑ WBC), blood cultures.
    • Paracentesis (if ascites): Ascitic fluid PMN count > 250 cells/mm³ is diagnostic for SBP.
    • Imaging: Upright X-ray (free air) or CT scan (abscess, definitive source).
  • Fix It (Treatment Algorithm):

⭐ For Spontaneous Bacterial Peritonitis (SBP), treatment is empiric antibiotics (e.g., 3rd-gen cephalosporin). Surgical intervention is typically NOT indicated, unlike secondary peritonitis.

High‑Yield Points - ⚡ Biggest Takeaways

  • Spontaneous Bacterial Peritonitis (SBP) is a key complication of cirrhosis and ascites, most commonly caused by E. coli. Diagnosis requires >250 neutrophils/mm³ in ascitic fluid.
  • Secondary peritonitis results from bowel perforation (e.g., appendicitis, diverticulitis) and is typically polymicrobial.
  • Peritoneal dialysis (PD)-associated peritonitis is often caused by skin flora like Staph aureus.
  • Classic signs include diffuse abdominal pain, rebound tenderness, and guarding.
  • Tuberculous peritonitis can present insidiously with a "doughy" abdomen and high ascitic fluid ADA.

Practice Questions: Peritonitis

Test your understanding with these related questions

A 40-year-old man presents with acute abdominal pain. Past medical history is significant for hepatitis C, complicated by multiple recent visits with associated ascites. His temperature is 38.3°C (100.9°F), heart rate is 115/min, blood pressure is 88/48 mm Hg, and respiratory rate is 16/min. On physical examination, the patient is alert and in moderate discomfort. Cardiopulmonary examination is unremarkable. Abdominal examination reveals distant bowel sounds on auscultation. There is also mild diffuse abdominal tenderness to palpation with guarding present. The remainder of the physical examination is unremarkable. A paracentesis is performed. Laboratory results are significant for the following: Leukocyte count 11,630/µL (with 94% neutrophils) Platelets 24,000/µL Hematocrit 29% Ascitic fluid analysis: Cell count 658 PMNs/µL Total protein 1.2 g/dL Glucose 24 mg/dL Gram stain Gram-negative rods Culture Culture yields growth of E. coli Which of the following is the next, best step in the management of this patient?

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Flashcards: Peritonitis

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Which form of IBD involves transmural inflammation with "knife-like" fissures? _____

TAP TO REVEAL ANSWER

Which form of IBD involves transmural inflammation with "knife-like" fissures? _____

Crohn disease

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