Peritonitis causes

• Perforation of the distal esophagus (Boerhaave syndrome)
  
• Perforation of the stomach (peptic ulcer, Gastric carcinoma)
  
• Perforation of the duodenum (peptic ulcer)
  
• Perforations of the remaining intestine (e.g. Appendicitis, Diverticulitis, Meckel diverticulum, IBD, Intestinal infarction, Intestinal strangulation, Colorectal carcinoma, Meconium peritonitis)
  
• Perforation of the gallbladder (cholecystitis)
  

Other possible causes for perforation

• Trauma
  
• Ingestion of a sharp foreign body (such as a fish bone)
  
• Perforation by an endoscope or catheter

Most common organisms -mixed bacteria

• Gram-negative bacilli (e.g. Escherichia coli), Anaerobic bacteria (e.g. Bacteroides fragilis)

• Trauma
  
• Surgical wound
  
• Peritoneal dialysis
  
• Chemotherapy
  

Most common organisms

• Mixed bacteria
  
• Staphylococcus aureus
  
• Coagulase-negative staphylococci
  
• Fungi such as Candida

Peritonitis occurring in the absence of an obvious source of contamination. It occurs either in children, or in patients with ascites.

e.g. Tuberculosis

• Blood(e.g.Endometriosis, Blunt abdominal trauma),
• Gastric juice (e.g.Peptic ulcer, Gastric carcinoma),
• Bile (e.g. Liver biopsy),
• Urine (e.g. Pelvic trauma),
• Menstruum (e.g. salpingitis),
• Pancreatic juice (pancreatitis),

These body fluids are sterile at first, they frequently become infected once they leak out of their organ, leading to infectious peritonitis within 24-48h.

Due to sterile foreign body inadvertently left in the abdomen after surgery (e.g. gauze, sponge)

• Familial Mediterranean fever
• Porphyria
• Systemic lupus erythematosus