R. R. is a 71-year-old female who presents with left lower quadrant pain that started out as cramping but has become more constant over the last day. She reports constipation over the last few days but admits that for as long as she can remember she has had variable bowel habits. Her vital signs are normal, but physical examination reveals some tenderness in the left lower quadrant. Which diagnostic test is most likely to support the leading differential diagnosis?
Correct Answer: B
Rationale: The correct answer is B: CBC with WBC differential. This test can help rule out infectious causes of left lower quadrant pain, such as diverticulitis or colitis, by assessing for elevated white blood cell count and left shift. A CT scan (A) with contrast may be indicated if the patient's condition worsens or if initial tests are inconclusive. Colonoscopy (C) is more appropriate for evaluating chronic or intermittent abdominal pain, not acute symptoms. Barium enema (D) is an outdated test and not commonly used for diagnosing acute abdominal pain.