Investigations

There are certain specialised investigations that can be used in the investigation of upper gastrointestinal (GI) conditions.

These do not replace a carefully taken history, but do provide a useful adjunct to clinical examination, and it is important to understand the uses and limitations of the various techniques.

Ultrasound

The use of high-frequency sound waves to image soft tissues is safe, effective, and widely available. The standard ultrasound examination involves a probe applied to the skin with a layer of conductive gel to provide a good interface for sound waves. These waves are produced in the probe at frequencies of 1-5 MHz and their reflections are collected and

Inferior vena cava

Left hepatic vein

Inferior vena cava

Left hepatic vein

Hepatic artery Portal vein

Common bile duct

Hepatic artery Portal vein

Common bile duct

Figure 12.2. (a) Anatomy of the biliary system (b) Portal segmentation.

interpreted to produce a real time gray-scale image of the area under investigation. Generally, fluid-filled structures transmit ultrasound waves easily and appear black, whereas connective tissues reflect more waves and appear brighter on the screen. Interpretation of ultrasound images is much easier when seen at the time of scanning, while printed images are more difficult. The experience of the operator is a very important factor in the accuracy of information provided. Basic trans-abdominal scanning is a useful investigation for biliary, hepatic and pancreatic disease, and can be combined with Doppler scanning technology (so-called 'duplex' scans) to give information about blood flow. Biopsy of intra-abdominal structures, such as liver metastases, can be performed accurately under ultrasound guidance, as can the insertion of drains. Using ultrasound through the layers of the anterior abdominal wall limits the image quality, and probes have been developed to allow use within the peritoneal cavity (handheld and laparoscopic), and within endoscopes. Endo-scopic ultrasound (EUS) is used to help stage upper GI malignancies, and investigate benign hepato-pancreato-biliary (HPB) conditions. Intra-operative ultrasound is also used for staging, and is helpful planning hepatic resections.

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