Which of the following is the gold standard diagnostic study for acute cholangitis?

The gold standard diagnostic study for acute cholangitis is endoscopic retrograde cholangiopancreatography (ERCP). This procedure not only allows for visualization of the bile ducts to confirm the diagnosis of cholangitis but also enables therapeutic interventions, such as removal of obstructive gallstones, which can relieve the infection's cause.

Acute cholangitis typically occurs due to an obstruction in the biliary tree, often from gallstones, and leads to bile duct infection. The hallmark of this condition is the presence of fever, jaundice, and right upper quadrant pain. ERCP helps visualize the anatomy of the bile duct and can effectively diagnose and treat the underlying obstruction, making it invaluable in this acute condition.

While ultrasound and CT scans are useful for assessing biliary obstruction and potential complications, they do not provide direct access to the bile ducts for both diagnosis and treatment. Angiography, on the other hand, is primarily used for vascular imaging and does not pertain to biliary tree evaluation. Thus, ERCP stands out as the most appropriate method for both diagnosing and managing acute cholangitis.