Peritonitis
GENERAL PRINCIPLES
• Primary or spontaneous bacterial peritonitis (SBP) is a common complication of cirrhosis and ascites. E. coli, K. pneumonia, and S. pneumoniae are common pathogens.
M. tuberculosis and Neisseria gonorrhoeae (Fitz-Hugh-Curtis syndrome) also can occasionally cause primary peritonitis (see Chapter 16, Sexually Transmitted Infections, Human Immunodeficiency Virus, and Acquired Immunodeficiency Syndrome).• Secondary peritonitis may be caused by a perforated viscus or contiguous spread from a visceral infection, usually resulting in an acute surgical abdomen.
• Peritonitis related to peritoneal dialysis is addressed in Chapter 13, Renal Diseases.
DIAGNOSIS
Clinical Presentation
SBP may present with abdominal pain without fever. SBP should be ruled out with a diagnostic paracentesis in patients with cirrhosis and ascites presenting with gastrointestinal bleeding, encephalopathy, acute kidney injury, or other decompensation of liver disease. Patients with secondary peritonitis present with abdominal tenderness and peritoneal signs.
Diagnostic Testing
• Send blood cultures and ascites fluid for culture (directly inoculate culture bottles at bedside), cell count, and differential. SBP is diagnosed when ascites fluid has >250 neutrophils/mm3.
• Diagnosis of secondary peritonitis is made clinically and with imaging to evaluate for free air (perforation) and the source of infection. Blood cultures should be obtained.
TREATMENT
• First-line treatment for SBP includes either a third-generation cephalosporin (e.g., ceftriaxone 2 g IV qday) or a fluoroquinolone (e.g., ciprofloxacin 400 mg IV q12h). Administration of IV albumin on days 1 and 3 of treatment may improve survival.29
• Treatment should be continued for 5 days. Extended courses may be needed for P. aeruginosa or resistant organisms.
• SBP prophylaxis with a fluoroquinolone or TMP-SMX should be initiated after the first episode of SBP or after variceal bleeding.
• Secondary peritonitis may require surgical intervention if there is perforation or intra-abdominal abscess. Anaerobic coverage with metronidazole 500 mg IV q8h should be added to above antibiotics. Antibiotics are continued until imaging demonstrates resolution of the abscess.