Differential Diagnosis for RLQ Pain

The patient presents with right lower quadrant (RLQ) pain, fever, and diarrhea, 12 days after an appendectomy for a ruptured appendix. Considering the history and symptoms, the differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis

  • Intra-abdominal Abscess: Given the recent history of a ruptured appendix and subsequent appendectomy, the development of an intra-abdominal abscess is highly plausible. The presence of fever and RLQ pain supports this diagnosis, as abscesses can form as a complication of the initial infection and surgery.

• Other Likely Diagnoses

  • Small Bowel Obstruction: This could be a complication of the recent surgery, especially if there was significant inflammation or if the bowel was inadvertently injured during the procedure. Symptoms like abdominal pain, fever, and changes in bowel habits (such as diarrhea) could be indicative of a partial obstruction.
  • Wound Infection: Although the pain is localized to the RLQ, a wound infection from the recent surgery could cause fever and localized pain, potentially radiating to the abdomen.
  • Adhesions: Early adhesions from the surgery could cause bowel obstruction or pain, though this might be less likely given the timeframe and the presence of diarrhea.

• Do Not Miss Diagnoses

  • Perforated Visus: Although less likely given the recent appendectomy, any viscus (such as the small intestine) that was damaged during the surgery or subsequently due to the disease process could perforate, leading to peritonitis. This condition is life-threatening and requires immediate intervention.
  • Hemorrhage: Internal bleeding as a complication of the surgery could present with abdominal pain, fever (if there's an associated infection), and potentially altered bowel habits due to blood in the intestines.

• Rare Diagnoses

  • Stump Appendicitis: Although rare, if a portion of the appendix was left behind during the appendectomy, it could become inflamed and cause symptoms similar to the initial appendicitis.
  • Intussusception: This is a condition where a part of the intestine slides into an adjacent part, potentially causing obstruction and ischemia. It's rare in adults and even more so in the context of recent abdominal surgery, but it could be considered if other diagnoses are ruled out.

The workup should include imaging studies such as a CT scan of the abdomen and pelvis to evaluate for abscesses, obstructions, or other complications. Blood work to assess for signs of infection or inflammation (e.g., elevated white blood cell count, C-reactive protein) and to evaluate the patient's overall condition is also crucial. Depending on the clinical picture, surgical consultation may be necessary for potential intervention.