What is indicated by mid-cycle lower abdominal pain that resolves spontaneously in an 18-year-old?

In an 18-year-old presenting with mid-cycle lower abdominal pain that resolves spontaneously, the most indicative condition is a ruptured ovarian cyst. This type of pain typically aligns with the menstrual cycle, often occurring around the time of ovulation, which can lead to the formation and potential rupture of ovarian cysts. The pain associated with a ruptured cyst is generally sharp and can vary in intensity; however, it may resolve on its own without the need for surgical intervention, aligning with the spontaneous resolution described in the scenario.

Other conditions, while they may present with abdominal pain, typically have more specific characteristics. Appendicitis usually presents as a more constant pain that worsens over time and would typically not resolve spontaneously. Ovarian torsion often causes severe, persistent pain and requires immediate medical attention; patients usually do not experience spontaneous resolution without treatment. Ectopic pregnancy may also present with abdominal pain, but it is usually associated with additional symptoms such as abnormal bleeding and would require medical evaluation, as it can pose significant health risks. Therefore, the spontaneous nature of the pain resolution strongly supports the diagnosis of a ruptured ovarian cyst in this age group.