**Question:** A patient came with lower chest trauma with pain in abdomen. His BP is 60/40 pulse 120 next best investigation

A. Chest X-ray
B. Abdominal X-ray
C. Chest CT scan
D. Abdominal ultrasound

**Core Concept:**
In the context of a patient with lower chest trauma presenting with both lower chest pain and abdominal pain, along with low blood pressure (hypotension) and tachycardia (rapid heart rate), we must consider the possibility of a hollow viscus injury. Hollow viscus injuries can lead to significant blood loss and result in the patient's symptoms and signs.

**Why the Correct Answer is Right:**
The correct answer, D (Abdominal ultrasound), is chosen because it is a non-invasive and quick imaging modality that can visualize the abdominal organs, including the hollow viscus. It can detect free fluid, intramural hematoma, and organ injury, thus helping in the diagnosis of abdominal viscus injury.

**Why Each Wrong Option is Incorrect:**
A. Chest X-ray (CXR) is essential to evaluate chest trauma but may not detect abdominal injuries. Chest injuries are the primary concern in this case, so a chest X-ray is a reasonable initial investigation.

B. Abdominal X-ray is less sensitive than abdominal ultrasound in detecting abdominal injuries. It is also less specific and can miss some significant findings.

C. Chest CT scan is a valuable tool in evaluating chest trauma but may not be the best choice for diagnosing abdominal injuries. Chest CT scan is more suitable for thoracic injuries and can be considered if no clear diagnosis is made after initial investigations.

**Clinical Pearl:**
The next best investigation in this scenario is abdominal ultrasound (option D). This is a crucial step in the diagnostic process as it can identify the cause of the patient's symptoms and guide further management. It allows for the visualization of the abdominal organs and can detect free fluid, intramural hematoma, and organ injury.

In summary, this patient presents with lower chest trauma and abdominal pain, alongside hypotension (low blood pressure) and tachycardia (rapid heart rate). The focus should be on diagnosing abdominal injury, and option D (abdominal ultrasound) is the most accurate method for diagnosing abdominal injuries, while considering the initial chest trauma.