救急外来に日本語を話せない40歳の外国人女性が来院した。病院に勤務している外国人医師が英語で医療面接と身体診察とを行い，記載した診療録の一部を示す。

Presenting complaint:
Severe lower abdominal pain.

History of presenting complaint:
Sudden onset of right lower abdominal pain 6 hours ago.
Pain has been gradually worsening.
Slight nausea but no vomiting or diarrhea.
Last menstruation was 9 weeks ago.
She noticed vaginal spotting* 3 days ago.

Past medical and social history:
Appendectomy at 18.
Married.

Examination:
Temperature 36.3℃
Right lower abdominal tenderness without rebound tenderness.
Bowel sounds are reduced.
　　　＊ vaginal spotting（少量の性器出血）

　可能性の高い疾患はどれか。