**Question:** A young female with 2 month amenorrhea presents with sudden abdominal pain with adnexal mass, urine pregnancy test is positive. Most likely diagnosis:

A. Ectopic pregnancy
B. Ovarian torsion
C. Endometriosis
D. Uterine rupture

**Core Concept:** Amenorrhea is the absence of menstrual periods, which can be primary (no menstruation before marriage) or secondary (loss of menstruation after regular periods). In the context of this question, the patient has secondary amenorrhea (>1 month absence of menstruation after regular periods). Abdominal pain with an adnexal mass indicates a potential gynecological issue, and a positive urine pregnancy test confirms the presence of a pregnancy.

**Why the Correct Answer is Right:** The correct answer is A. Ectopic pregnancy. Ectopic pregnancy occurs when the fertilized egg implants outside the uterus, most commonly in the fallopian tube. This patient's symptoms align with an ectopic pregnancy, as the abdominal pain with an adnexal mass indicates an implanted pregnancy outside the uterus. The urine pregnancy test confirms a pregnancy, but since the patient has secondary amenorrhea, the pregnancy is unlikely to be in the uterus.

**Why Each Wrong Option is Incorrect:**

Option B, Ovarian torsion, involves a twisting of the ovary, causing pain and sometimes meets a mass. However, the absence of menstruation and a positive urine pregnancy test are against this diagnosis.

Option C, Endometriosis, is the presence of endometrial tissue in ectopic locations, typically involving chronic pelvic pain. Although the patient has abdominal pain, the sudden presentation and positive urine pregnancy test make endometriosis less likely.

Option D, Uterine rupture, is a tear in the uterus, usually due to trauma or natural causes like age. The absence of menstruation and a positive urine pregnancy test are against this diagnosis.

**Clinical Pearl:**

Unexplained acute abdominal pain in a young female with a positive urine pregnancy test should prompt a thorough workup for an ectopic pregnancy, as the uterus is less likely. This clinical scenario is vital for medical students and residents to understand, as misdiagnosis can have severe consequences, including rupture and life-threatening hemorrhage.