Radiology and endoscopy are the principal investigations. These are usually preceded by routine haematology and biochemistry.
Plain X-rays of the abdomen are chiefly used in the investigation of acute abdomen (see p. 233). Areas of calcification can be seen in chronic pancreatitis. Routine abdominal X-rays are of little use in the management of most gastrointestinal disease. Barium contrast studies.
The oesophagus is visualized as barium is swallowed in the upright and prone positions. Motility abnormalities as well as anatomical lesions can then be observed. Reflux of barium from the stomach into the oesophagus is demonstrated with the patient tipped head down, but minimal reflux under these conditions may well have no clinical significance.
Swallowing bread with the barium (to add bulk) is sometimes useful in a difficult case of dysphagia.
This is performed to examine the stomach and duodenum. A small amount of barium is given together with effervescent granules or tablets to produce carbon dioxide so that a double contrast between air and barium is obtained. This technique has a high accuracy rate when performed carefully. Single-contrast studies are not recommended. Small bowel follow-through This is used to examine the small bowel and ideally should be performed separately from a barium meal as a different technique is employed. Barium is swallowed and allowed to pass into the small intestine through the jejunum and into the ileum. This technique is the only way of demonstrating the gross anatomy of the small intestine. Views of the terminal ileum should be obtained with the use of a compression pad.Small bowel enema (enteroclysis) A tube is passed through the duodenum and a large volume of dilute barium is introduced. This technique is useful for visualizing suspicious areas seen on the followthrough particularly strictures.
Barium and air are insufflated into the rectum via a retained catheter. A double-contrast view is then obtained of the whole colon, often with views of the terminal ileum as well. The patient must be prepared well with laxatives and wash-outs so that the colon is empty. Rectal examination and sigmoidoscopy usually precede this examination.
Abdominal ultrasound. computed tomography (cr) and magnetic resonance imaging (MRI) These techniques are being increasingly used for detecting thickened bowel, masses, abscesses and fistulas in, for example, Crohn’s disease or tuberculosis. CT, endoscopic ultrasound and MRI are also being used for evaluating tumour size and spread.
Video endoscopes producing images of high quality are now available. This technical advance allows easy data collection.
OESOPHAGOGASTRODUODENOSCOPY (OGD) is often used as the investigation of choice for upper gastrointestinal disorders by gastroenterologists because of easy access, the possibility of interventional therapy and obtaining mucosal biopsies.
COLONOSCOPY allows good visualization of the whole colon and terminal ileum. Biopsies can be obtained and polyps removed. The success rate for reaching the terminal ileum is approximately 80% and the mortality is 1 : 100000. The major complication is perforation. Barium studies and endoscopy are frequently complementary and the technique chosen often depends on local expertise and work-load. Radiology is better than endoscopy for assessing motility disorders, extrinsic lesions and gastro-oesophageal reflux. Endoscopy is preferable in gastric ulcer disease (as biopsies can be obtained) and in the detection of oesophagitis. Colonoscopy is used in the sick immobile patient, in inflammatory bowel disease, for polyp follow-up and in the investigation of rectal bleeding. Barium enema is usually performed for the investigation of change in bowel habit.
Radionuclides are used to a varying degree depending on local enthusiasm and expertise. Indications are:
• To demonstrate oesophageal reflux using [99mTc]sul_ phur colloid
• To determine the rate of gastric emptying using [99mTc]-sulphur colloid
• To demonstrate a Meckel’s diverticulum using [99mTc] pertechnetate which has an affinity for gastric mucosa
• To show inflammation and an inflammatory mass in inflammatory bowel disease using IIIIn-labelied white cells
• Isotopic techniques can also be used to assess gastrointestinal loss of red cells, albumin and bile acids, and the retention of vitamin B12.