**Question:** A 31-year-old woman comes to the emergency department because of abdominal pain and vaginal spotting. She states that the pain began 2 days ago and has been worsening since. The spotting occurred this morning. Her last menstrual period was 6 weeks ago. She has no medical problems. She takes no medications and has no known drug allergies. Her temperature is 37°C (98.6°F), blood pressure is 90/50 mmHg, pulse is 110/minute, and respirations are 14/minute. Abdominal examination reveals significant lower abdominal tenderness. Speculum examination shows scant blood in the vagina with a closed cervical os. Bimanual examination demonstrates significant left adnexal tenderness. Urine hCG is positive. Serum hCG is 5,000 mIU/mL. Pelvic ultrasound shows a normal uterus with a left adnexal mass surrounded by free fluid. Which of the following is the most likely diagnosis?

A. Ectopic pregnancy
B. Endometriosis
C. Ovarian cyst
D. Uterine fibroid

**Core Concept:**

The presented case describes a patient experiencing abdominal pain, vaginal spotting, and laboratory findings indicative of a hormonal disorder. The patient has a history of recent pregnancy, an elevated urine beta-human chorionic gonadotropin (beta-hCG) level, and ultrasound findings of a left adnexal mass surrounded by free fluid. These symptoms and findings are consistent with an ectopic pregnancy.

**Why the Correct Answer is A:**

The correct answer is **A** Ectopic pregnancy because of the following points:

1. The presence of lower abdominal pain and vaginal spotting are common clinical features of an ectopic pregnancy.
2. The elevated serum beta-hCG levels (5,000 mIU/mL) are indicative of a pregnancy complication.
3. The ultrasound finding of a left adnexal mass surrounded by free fluid is consistent with an ectopic pregnancy.
4. The patient has no known medical history or medications that would be associated with other conditions (e.g., Endometriosis, fibroids, or uterine fibroids).

**Why Other Options are Incorrect:**

B - Endometriosis: Although pain can be present in endometriosis, the ultrasound findings are not specific to this condition.
C - Ovarian cyst: An ectopic pregnancy can also cause abdominal pain, but the ultrasound finding of a left adnexal mass surrounded by free fluid is specific to an ectopic pregnancy.
D - Uterine fibroid: Uterine fibroids are typically asymptomatic unless they become large, and ultrasound findings are not specific to fibroids.

**Clinical Pearl:** Ectopic pregnancies are a significant health concern due to the risk of rupture and life-threatening hemorrhage. Prompt diagnosis and management are essential to prevent complications.