13. Imaging of the esophagus, stomach and small bowels. Methods, indications, imaging strategy.

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Upper endoscopy

Upper endoscopy, also called oesophago-gastro-duodenoscopy (EGD) is a procedure which involves endoscopic examination of the entire upper GI-tract, the oesophagus, stomach, and duodenum. It's a commonly used procedure which can be used to evaluate a variety of conditions in three different organs. It uses a flexible scope.

Indications

Upper endoscopy is used acutely in case of suspected acute upper gastrointestinal bleeding. Other indications include:

During the procedure, several instruments may be used to treat pathology, such as diathemy to treat polyps. One can also make biopsy, cytology, or microbiological tests.

Endoscopic ultrasonography

Upper endoscopy can be combined with ultrasound, called endoscopic ultrasonography or endosonograpgy. Ultrasound from inside the upper GI tract sometimes allows for better visualisation of the oesophagus, pancreas, biliary tree, and mediastinum than cross-sectional imaging (CT or MRI) or abdominal ultrasound.

This is especially used in case of oesophageal cancer, to determine depth and spread.

Complications

Complications are rare but may include perforation or bleeding.


Other investigations of the oesophagus

Investigations for gastroesophageal reflux disease

Many modalities may be used in gastroesophageal reflux disease:

Oesophageal pH monitoring

Oesophageal pH can be monitored by a probe or wireless capsule placed in the stomach near the lower oesophagus for 24 hours, allowing measurement of acid in the distal oesophagus.

Oesophageal impedance

Oesophageal impedance measures the flow of reflux into the oesophagus. It works on the principle of measuring impedance (resistance to electrical flow). It can measure reflux of gas and liquid, not only pH. It’s often measured simultaneously as pH monitoring detailed above with the same device.

Bilitec

Bilitec® detects bilirubin in the oesophagus and is a test for biliary reflux.

Investigations for oesophageal motility disorders

These investigations are used for the diagnosis of oesophageal motility disorders like achalasia or diffuse oesophageal spasm.

  • Oesophageal manometry
  • Barium swallow

Oesophageal manometry

Manometry is the gold standard for diagnosis of motility disorders. It uses a transnasal catheter with pressure sensors to analyse pressure at different points in the oesophagus, allowing analysis of the peristaltic waves in the oesophagus.

Barium swallow

Barium swallow, also called an oesophagogram, involves making the patient swallow barium contrast while the oesophagus is imaged by fluoroscopy. This allows visualisation of food moving through the oesophagus in real time. A "filling defect" on the barium swallow, defined as a portion of the oesophagus which isn't filled by the barium contrast, can be due to:

A double-contrast oesophagogram refers to when barium is swallowed first, then air or CO2 releasing tablets.

Barium is contraindicated in

  • Suspicion of perforation of GI tract
  • After GI surgery
  • High risk for aspiration

If barium is contraindicated, gastrographin is used instead. It is a water-soluble, iodinated contrast agent. Barium leak can cause necrotizing peritonitis.

Investigations for oesophageal cancer

The diagnosis of oesophageal cancer is histologic, and a biopsy is obtained by upper endoscopy (oesophagoscopy).

CT and PET-CT are also important in the evaluation of oesophageal cancer but somewhat out of the scope of the topic.


Investigations of the small intestine

Enterography refers to imaging of the small intestine. It may be performed with simple x-ray (often called just enterography), CT enterography, or MR enterography.

Indications

It may be used to evaluate for:

Patient preparation

Ahead of the examination, the patient should fast for 6 hours, to reduce the activity and movement of the small intestine. A moderate laxative like lactulose can be used.

Procedure

During the procedure, Buscopan® (butylscopolamine, an anticholinergic) or glucagon may be administered to slow intestinal motility, reducing motion artifacts.

Interpretation

With simple x-ray enterography, not much information is gathered and so it is rarely used. It may be able to visualise ileus, in which case the diameter of the small bowel is > 3 cm, or perforation, in which case there is air in the abdomen. CT and MR give much more information and are more frequently used.

Presence of air in the bowel wall is called pneumatosis intestinalis and is seen in intestinal ischaemia or necrotising enterocolitis.

The presence of the "double bubble sign" on enterography is typical for duodenal atresia.

Enteroclysis

Enteroclysis refers to usage of fluoroscopy and oral contrast to visualise the movement of foodstuff through the small bowel. The oral contrast used is barium, given together with methylcellulose. Methylcellulose is not a contrast agent itself, but it increases the volume of the contrast material. Methylcellulose has low x-ray absorbance (it’s radiolucent). Barium and methylcellulose are administered by nasoduodenal tube.