Performing ERCP in children involves the use of a flexible endoscope inserted through the mouth, down the esophagus, and into the stomach and duodenum. A contrast dye is injected into the bile and pancreatic ducts through a small tube passed through the endoscope. This allows for detailed X-ray images of these structures. Interventions such as stone removal, stent placement, or biopsy can also be conducted during the procedure.