As ultrasounds are easily interfered by gas echoes, it is rather difficult to interrogate all parts of the biliary tract. We should make the best use of the manipulation of the probe, different postures and different respiratory phases to get good images free from air in the gastrointestinal tract. It is also important to know about the characteristics of artifacts on ultrasonography and how to remove their influence.
In gallbladder lesions, we first classify the shape of the lesions on ultrasonography into the pedunclated type, broad based type and wall-thickened (flat) type. This classification is very important not only to make a differential diagnosis, but also to evaluate the depth of the invasion. Then, we evaluate their size, surface structure, internal echo texture, the layer structure of the gall bladder wall where tumors are attached, and so on. Those findings are useful to discriminate pseudotumor from cancer and adenoma.
In the extra hepatic bile duct and the papilla of Vater, it is much more difficult to detect lesions because of the complicated anatomical structure and air in the gastrointestinal tract. So, it is important to pick up indirect findings to suggest latent lesions. We can use bile duct dilatation, abnormal findings in the gallbladder, debris in bile ducts and lymph node. Abnormal findings in the gallbladder, which include distension with or without debris and impaired fullness, are most sensitive to the obstruction of the biliary tract. We sometimes use serial ultrasonography to assess characters of lesions in addition to evaluating the same findings, which we discussed in gallbladder lesions. If the lesions change their appearance on serial ultrasonography, they have a high possibility of being pseudotumor.
With improved skill using ultrasonography and accurate knowledge, ultrasonography could become much more effective on erraPnin Y of the hiliarv tract
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