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How do contrast dyes and X-rays show blocked pancreatic or bile ducts?

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An anatomical illustration of the human pancreas shows its location near the stomach and intestines, a detailed cross-section highlighting ducts and the islet of Langerhans, and an inset of pancreatic tissue histology with labeled alpha, beta, and delta cells. — pancreatic cancer The human pancreas is composed of two main types of tissue: acinar cells and islets of Langerhans. The acinar cells produce digestive enzymes, which are secreted into tiny ducts that feed into the pancreatic duct. Islets of Langerhans are clusters of cells that secrete hormones such as insulin and glucagon directly into a capillary network, which also joins the pancreatic duct.

To visualize blocked pancreatic or bile ducts, medical professionals use a procedure called endoscopic retrograde cholangiopancreatoscopy (ERCP).

During this procedure, an endoscope is passed through the stomach into the duodenum to locate the ampulla of Vater, which is the opening where the common bile duct enters the small intestine. Once this area is accessed, a radiopaque dye is injected into the ducts.1

Because the dye is radiopaque, it blocks X-rays, allowing the ducts to appear clearly on radiographic images. This visualization enables physicians to identify obstructions caused by tumours, gallstones, or inflammation. If a blockage is confirmed, the procedure can sometimes be used to treat the obstruction, such as by enlarging the opening of the duct or placing a stent to restore flow.12