Other applications of IOUS

There are numerous extrahepatic applications for IOUS in the abdomen, including urological, vascular and gastrointestinal tract scanning. Ultrasound evaluation of the common duct for calculi following cholecystectomy can identify small fragments which may not be easily palpable through the duct wall. Using this technique the duct is less susceptible to injury which may be associated with direct examination or the introduction of X-ray contrast agents. Pancreatic scanning is particularly useful in identifying small tumours of the body and tail of pancreas for curative resection16 and in differentiating small pancreatic retention cysts from solid nodules.
The treatment of tumours by percutaneous ultrasound- guided techniques, rather than surgical resection, is becoming more common. However, it may not always be possible to achieve success percutaneously and techniques have been developed to ablate tumours during open surgery. Cryotherapy,18 in which the lesion is frozen by introducing a cryoprobe into the centre of the lesion under intraoperative ultrasound guidance, has been successfully used, but is now largely superseded by radiofrequency and microwave ablation (Fig.ultrasound images below).
The RF probe is introduced into the metastasis under intraoperative ultrasound guidance.
The lesion is gradually ablated; the area of ablated tissue reflects the sound and can be seen to increase in size progressively during the course of the therapy These techniques have resulted in long-term survival in patients with hepatocellular carcinoma19 and multiple liver metastases.20 The success of such techniques depends to a large extent upon patient selection. Those with very large and/or multiple lesions tend to have a poor prognosis compared with patients with smaller, well-confined disease. However these techniques continue to develop and are likely to offer hope to many patients currently untreatable with conventional methods.
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