Suprapubic Abdominal Pain

12 year old female, previously healthy, presented with 6 hours history of suprapubic severe abdominal pain without fever, nausea, vomiting or diarrhea. No other symptoms. She is due for her menstrual period. She had a milder pain in the same location last month during her menstrual period. On physical exam: T: 36.5, P: 110, BP: 130/90, RR: 25. There is suprapubic abdominal tenderness with rebound. Psoas sign is negative. Urinalysis is negative for WBC, leukocyte esterase and nitrate. CBC showed total WBC of 18800, polymorphonuclears are 88%. CT scan of abdomen and pelvis with IV and PO contrast is shown below:

What is the most probable diagnosis?

1. Dysmenorrhea
2. Urinary tract infections
3. Appendicitis
4. Abdominal mass