Thickening of the Bile Duct Wall

Transcutaneous ultrasonography can assess localized benign thickening of the bile duct wall in two disorders of the biliary system: intrahepatic and extrahepatic presentation of primary sclerosing cholangitis (PSC) (Fig. 3.6), and the solely extrahepatic manifestation of (severe) suppurative cholangitis (Fig. 3.7). Except for a few cases, in both instances the sonographic morphology cannot be considered as primary proof but rather “suggests” the suspected diagnosis, with a greater or lesser degree of probability, which then will have to be confirmed by other means (clinical findings,

blood chemistry, and endoscopic retrograde cholangiography).

The prolonged course of chronic inflammatory bowel disease (Crohn disease, ulcerative colitis) is often accompanied by the sonographic telltale signs of PSC, from segmental diffuse bile duct wall thickening all the way to complete obstruction of the lumen, alternating with dilated/ectatic bile duct segments; ducts may also appear simply to break off, and intraductal sludge is a frequent finding (Fig. 3.6a,b). It is not possible to rule out early cholangiocellular carcinoma (CCC), and even fine-needle aspiration cytology has its prob-

lems. PSC-like changes have been described for HIV infections with manifest AIDS symptoms.

Acute suppurative cholangitis may result in thickening of the common duct wall, which can be demonstrated for the extrahepatic segment. This thickening of the wall becomes particularly evident if endoscopic intervention (endoscopic papillotomy, EPT) has provided pressure relief by removing or bypassing the biliary obstruction: the dilated bile duct walls, originally thinned out by their distension, collapse and their inflamed and swollen true structure becomes exceptionally well visualized (Fig. 3.7a).

Malignant bile duct wall thickening may be localized as in CCC or infiltrating as in hepatocellular carcinoma (HCC), and in both cases ultrasound detects these changes solely in terms of the resulting biliary obstruction with its subsequent prestenotic dilatation of the duct. Consequently, these entities are discussed

in the section on pressure-induced bile duct dilatation.

One rare special case is mucinous biliary papillomatosis with its fluent transition to well-differentiated cholangiocarcinoma (Fig. 3.8). The ultrasound findings show a nonexpansile solid mass originating in the surrounding bile duct wall, which it dilates to

sometimes bizarre shapes, but well defined and demarcated from the bile duct wall itself; complete biliary obstruction tends to occur late in the disease. It has a rather indolent course (over many years), and treatment is characterized by effective long-term interventional endoscopy (stenting, removal of the tumor masses).