Review Question - QID 109548

A 23-year-old woman presents to the emergency department with abdominal pain. The patient states that she has pain in her back that radiates to her abdomen. The pain started yesterday and is episodic. She describes the pain as a 10/10 when it occurs. The patient has a past medical history of asthma, anxiety, and chlamydia that was appropriately treated. Her current medications include fluoxetine. The patient's lab values are ordered as seen below.

Hemoglobin: 14 g/dL
Hematocrit: 40%
Leukocyte count: 8,500 cells/mm^3 with normal differential
Platelet count: 225,000/mm^3

Serum:
Na+: 140 mEq/L
Cl-: 100 mEq/L
K+: 4.9 mEq/L
HCO3-: 24 mEq/L
BUN: 22 mg/dL
Glucose: 89 mg/dL
Creatinine: 1.2 mg/dL
Ca2+: 10.0 mg/dL
AST: 11 U/L
ALT: 11 U/L

Urine:
Color: amber
Nitrites: negative
Na+: 12 mmol/24 hours
Beta-hCG: positive
Red blood cells: 11/hpf

Which of the following is the most appropriate test for this patient's most likely diagnosis?