A 33-year-old woman with a past medical history of Crohn's disease, depression, and pelvic inflammatory disease presents to the emergency department with abdominal pain, nausea, and vomiting. She states that her symptoms started yesterday and have been worsening. She has been unable to have a bowel movement, and every time she eats, she vomits shortly afterward. Her initial vitals are unremarkable, and a physical exam shows a distended and tympanic abdomen. One hour later, the patient complains of worsening abdominal pain. Her temperature is 97.9 °F (36.6 °C), blood pressure is 104/64 mmHg, pulse is 140/min, respirations are 12/min, and oxygen saturation is 98%.

Laboratory results:
- Hemoglobin: 14 g/dL
- Hematocrit: 44%
- Leukocyte count: 10,500/mm³ with normal differential
- Platelet count: 233,000/mm³
- Lactate: 5 mmol/L (normal < 1.0 mmol/L)

The patient's exam is notable for significant rebound tenderness. Which of the following is the most appropriate next step in management?

1) CT abdomen/pelvis
2) MRI abdomen/pelvis
3) Nasogastric tube
4) Transvaginal ultrasound
5) Urgent surgery

The most appropriate next step in the management of this patient, considering the signs of a potential acute abdomen condition and elevated lactate, is to perform a CT abdomen/pelvis to quickly identify the cause and determine the need for urgent surgery.

Explanation:

The patient's presentation of abdominal pain, nausea, vomiting, inability to have a bowel movement, abdominal distention, tympanism, and the presence of rebound tenderness are concerning findings that could suggest an acute abdomen situation. The elevated lactate level is worrisome for ischemia or a severe infection. Given the clinical urgency and the patient's worsening condition, immediate diagnostic imaging is warranted. The goal is to quickly determine the cause of the acute abdomen and proceed with proper management.

The most appropriate next step in management, given the suspicion of an acute abdomen, is to perform a CT abdomen/pelvis. This imaging method is efficient at providing a broad view of abdominal structures, helping to detect any signs of obstruction, perforation, ischemia, or other potentially life-threatening issues. In the context of worsening symptoms and significant rebound tenderness, with potential red flags for an abdominal catastrophe, urgent surgical consultation should be considered after obtaining the imaging results to decide on the necessity of urgent surgery. Although other options such as MRI abdomen/pelvis, nasogastric tube, and transvaginal ultrasound could be useful in certain scenarios, they are not the most appropriate or immediate next steps given the clinical urgency.