Differential Diagnosis for Lower Right Abdominal Pain

Given the clinical presentation and imaging findings, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Early Appendicitis: The appendix measures 8 mm, which is slightly above the normal threshold, and there's a mention that early mild appendicitis cannot be excluded. Clinical correlation with symptoms such as lower right abdominal pain, fever, and laboratory findings like elevated white blood cell count would support this diagnosis.

• Other Likely Diagnoses

  • Mesenteric Lymphadenitis: This condition can present with similar symptoms to appendicitis, including lower right abdominal pain, and can be associated with lymph node enlargement in the mesentery.
  • Ovarian Cyst or Torsion: In female patients, ovarian cysts or torsion can cause severe lower abdominal pain and might not always have specific findings on imaging unless there's significant ovarian enlargement or torsion.
  • Diverticulitis: Although more common on the left side, diverticulitis can occur on the right and cause lower right abdominal pain, especially if there are diverticula in the right colon.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: A critical diagnosis to consider in females of childbearing age presenting with lower abdominal pain, which can be life-threatening if missed.
  • Intestinal Obstruction: Can cause severe abdominal pain and may not always have obvious findings on initial imaging, requiring careful clinical assessment and possibly further diagnostic tests.
  • Inflammatory Bowel Disease (IBD) Flare: Conditions like Crohn's disease or ulcerative colitis can cause lower right abdominal pain and may have non-specific findings on imaging, requiring clinical and laboratory correlation.

• Rare Diagnoses

  • Meckel's Diverticulitis: A rare condition where a congenital diverticulum of the small intestine becomes inflamed, which can mimic appendicitis.
  • Retrocecal Appendicitis: Although not rare, its atypical location can sometimes make diagnosis challenging, and it might not always present with the classic symptoms of appendicitis.
  • Right Lower Lobe Pneumonia: Can cause referred abdominal pain and should be considered, especially if there are respiratory symptoms or findings on chest imaging.