Final answer:
To confirm esophageal perforation when subcutaneous emphysema is observed, a contrast esophagram is the primary diagnostic test, although chest radiography and CT scans may also be utilized.
Step-by-step explanation:
If you suspect esophageal perforation and observe subcutaneous emphysema, the primary diagnostic test that should be performed to confirm the diagnosis is a contrast esophagram (also known as a barium swallow). This test involves swallowing a contrast agent like barium, which allows visualization of the esophagus on X-ray images. If there is perforation, the contrast medium may leak into surrounding tissues or spaces, clearly indicating a breach in the esophageal wall. Although endoscopic procedures such as endoscopic ultrasound are useful for other conditions like gallstones or pancreatitis, they are not the first choice for diagnosing esophageal perforation due to the risk of worsening the perforation. Other diagnostic options include chest radiograph which may show air in the mediastinum or pleural cavities, and computed tomography (CT) scan which is more sensitive and can also provide detailed images of the esophagus and surrounding structures.