Differential Diagnosis

The patient's presentation of lower abdominal pain, tenderness to palpation on the right lower abdomen with rebound tenderness, and specific hip movements that exacerbate or relieve pain suggests several possible diagnoses. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Appendicitis: The combination of lower abdominal pain, tenderness to palpation, rebound tenderness, and pain upon extension of the hip (which can irritate the peritoneum near the appendix) but relief with hip flexion is highly suggestive of appendicitis. The improvement of pain with hip flexion is consistent with the psoas sign, a classic indicator of appendicitis.

• Other Likely Diagnoses

  • Ovarian Cyst or Torsion: While the absence of pain with internal and external rotation of the hip might seem less typical, ovarian pathology can sometimes present with atypical symptoms. The lower abdominal pain and tenderness could be related to an ovarian cyst, especially if it's ruptured or torsioned.
  • Diverticulitis: Although more common on the left side, diverticulitis can occur on the right and present with lower abdominal pain and tenderness. However, the specific relationship with hip movement is less characteristic.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: Although less likely if the patient is not of childbearing age or if a pregnancy test is negative, ectopic pregnancy is a critical diagnosis to consider due to its potential for severe consequences, including death. It can present with lower abdominal pain and tenderness.
  • Ruptured Aneurysm or Aortic Dissection: These are less likely given the specific symptoms but are critical to rule out due to their high mortality rate. Abdominal pain can be a presenting symptom, and while the pattern of pain with hip movement is not typical, the severity of these conditions warrants consideration.

• Rare Diagnoses

  • Psoas Abscess: An abscess in the psoas muscle can cause lower abdominal pain that worsens with extension of the hip (psoas sign) and improves with flexion. It's less common and usually associated with specific risk factors like recent spinal surgery or intravenous drug use.
  • Intra-abdominal or Retroperitoneal Tumors: Certain tumors can cause abdominal pain and tenderness, and while rare, they should be considered in the differential diagnosis, especially if other symptoms or risk factors are present.