Case of the Week — Case #2: "I fell and my belly hurts"

25 year-old female presents to the ED after slipping on water in her kitchen and falling to the ground yesterday. She denies loss of consciousness, but complains of abdominal pain and began vaginal spotting today. She states that she is 8 weeks pregnant confirmed by her primary doctor. This is her first pregnancy and has been receiving prenatal care, but has not had her first ultrasound as of yet. She denies chest pain, headache, nausea, vomiting or extremity pain. Physical exam reveals a diffusely tender abdomen, without other signs of trauma. Pelvic exam is positive for scant blood in the vaginal vault, but a thick closed os and no cervical motion tenderness or adnexal masses palpable. Labs included a normal CBC and a quantitative bHCG of 61,410. The resident performs a transabdominal bedside ultrasound. What is the diagnosis?