Differential Diagnosis for Marked Inflammatory Changes in the Peritoneum without a Mass on MRI

• Single most likely diagnosis:
  • Peritonitis: This is the most likely diagnosis given the marked inflammatory changes in the peritoneum. Peritonitis is an inflammation of the peritoneum, typically caused by a bacterial infection. The absence of a mass on MRI supports this diagnosis, as peritonitis does not typically present with a discrete mass.
• Other Likely diagnoses:
  • Diverticulitis: Although more commonly associated with the colon, diverticulitis can cause peritoneal inflammation if the diverticula rupture. The lack of a mass on MRI could be due to the inflammatory process not being localized enough to form a distinct mass.
  • Appendicitis: Similar to diverticulitis, appendicitis can cause peritoneal inflammation, especially if the appendix ruptures. The absence of a mass might indicate that the appendix is not significantly enlarged or that the inflammation is more diffuse.
  • Pelvic Inflammatory Disease (PID): PID can cause inflammation of the peritoneum, particularly in the pelvic region. It might not present with a distinct mass on MRI, especially if the infection is not localized to a specific organ like the ovaries or fallopian tubes.
• Do Not Miss diagnoses:
  • Ruptured Viseral Organ (e.g., spleen, liver): Although these conditions might present with more acute symptoms and potentially a mass or free fluid on imaging, it's crucial not to miss them due to their high mortality rate if not promptly treated.
  • Bowel Perforation: Any condition leading to bowel perforation (e.g., ulcer, trauma) can cause peritoneal inflammation. Missing this diagnosis could lead to severe consequences, including sepsis and death.
• Rare diagnoses:
  • Familial Mediterranean Fever (FMF): A genetic disorder that can cause recurrent episodes of peritoneal inflammation among other symptoms. It's rare and might not be initially considered but is important to diagnose for appropriate management.
  • Eosinophilic Peritonitis: A rare condition characterized by eosinophilic infiltration of the peritoneum, which can cause inflammation. It might be associated with parasitic infections, drugs, or systemic diseases.
  • Tuberculous Peritonitis: Although more common in certain geographic regions, tuberculous peritonitis is a rare cause of peritoneal inflammation in many parts of the world. It can present with chronic symptoms and might not always show a distinct mass on imaging.