Differential Diagnosis for Peritonitis

When diagnosing peritonitis, it's crucial to consider a wide range of potential causes due to the severity and variability of the condition. Here's a structured approach to the differential diagnosis:

• Single Most Likely Diagnosis

  • Spontaneous Bacterial Peritonitis (SBP): This is a common cause of peritonitis, especially in patients with cirrhosis and ascites. The presence of bacteria in the ascitic fluid without any apparent source of infection, such as a surgical wound or perforated viscus, characterizes SBP.

• Other Likely Diagnoses

  • Perforated Peptic Ulcer: A perforation in the stomach or duodenum can lead to the leakage of digestive enzymes and bacteria into the peritoneal cavity, causing peritonitis.
  • Appendicitis: Although appendicitis typically presents with localized pain, a perforated appendix can spread infection to the peritoneum, leading to peritonitis.
  • Diverticulitis: Complicated diverticulitis, where the diverticula rupture, can cause peritonitis.
  • Cholecystitis: In severe cases, especially if a gallbladder perforates, cholecystitis can lead to peritonitis.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: A ruptured ectopic pregnancy can cause severe abdominal pain and peritonitis due to blood irritating the peritoneum.
  • Ovarian Torsion: While not typically causing peritonitis directly, the necrosis of ovarian tissue can lead to peritoneal irritation and mimic peritonitis.
  • Mesenteric Ischemia: This condition, resulting from decreased blood flow to the intestines, can cause bowel infarction and subsequent peritonitis.

• Rare Diagnoses

  • Tuberculous Peritonitis: A form of peritonitis caused by Mycobacterium tuberculosis, more common in areas with high TB prevalence or in immunocompromised patients.
  • Fungal Peritonitis: Typically seen in immunocompromised patients or those on long-term peritoneal dialysis.
  • Pneumococcal Peritonitis: Caused by Streptococcus pneumoniae, this is a rare cause of spontaneous peritonitis, often associated with pneumonia or other infections.
  • Peritoneal Carcinomatosis: Metastasis to the peritoneum from abdominal or pelvic malignancies can cause peritonitis, either through direct invasion or obstruction of bowel or tubes.

Each of these diagnoses has distinct clinical presentations, risk factors, and diagnostic approaches. A thorough history, physical examination, laboratory tests (including peritoneal fluid analysis), and imaging studies are essential for accurately diagnosing the cause of peritonitis.