Biliary dilatation

What it means

The liver makes bile, a green-yellow fluid that helps digest fat. Bile travels through a network of tubes — the biliary tree — that joins together into the common bile duct and empties into the small intestine. When bile can't drain freely, the tubes upstream of the holdup stretch like a backed-up river. On a CT or MRI, the radiologist sees those normally hair-thin tubes looking wider, sometimes much wider, than they should.

Why it appears on a CT or MRI report

Reports usually describe where the widening is (inside the liver, outside the liver, or both), how wide the ducts measure in millimetres, and whether the radiologist can see a cause further down — a stone in the duct, a narrowing of the duct wall, an inflamed pancreas head, or a mass. Some reports add specific terms like intrahepatic for ducts within the liver and extrahepatic for the common bile duct. A widened pancreatic duct alongside the bile duct is called the double-duct sign and is taken seriously.

What it usually means

The most common cause is a gallstone that has slipped out of the gallbladder and lodged in the bile duct. Inflammation or scarring of the duct from previous infections or procedures can narrow it. In older adults, a new widening without a stone raises concern for a tumour of the pancreas head, the duct itself, or the area where the duct meets the bowel. A mild widening can also be a normal aftermath of having the gallbladder removed — the duct sometimes compensates by expanding slightly. The clinical picture matters: jaundice, dark urine, pale stools, itching, fever, or pain in the upper-right belly all sharpen the urgency. Bloodwork showing rising liver enzymes or bilirubin pushes the work-up faster.

When to follow up

Talk to your doctor about the report promptly, especially if it mentions widening of multiple ducts, a measurable cause, or pairs with abnormal liver blood tests. Yellow skin or eyes, dark tea-coloured urine, pale or clay-coloured stools, persistent itching, fever with chills, or upper-right belly pain are red-flag symptoms that warrant same-day attention. Your clinician will often order a focused MRI of the ducts (an MRCP) or refer to a gastroenterologist for a closer look from inside the bowel using a flexible camera.

A plain-language way to picture it

Imagine the liver as a tree and the ducts as its branches and trunk, draining sap downward into a tap at the bottom. If a stone or pinch closes the tap, sap still keeps being made up in the leaves, so it backs up — first the trunk swells, then the bigger branches, then the smaller twigs. Radiologists trace that swelling backwards from the trunk to find the spot where the tap is jammed.