Gastrointestinal tract

Published on 01/04/2015 by admin

Filed under Radiology

Last modified 01/04/2015

Print this page

This article have been viewed 2570 times

Chapter 3 Gastrointestinal tract

Methods of imaging the gastrointestinal tract

2. Barium swallow

4. Barium follow-through

5. Small bowel enema

6. Barium enema

7. Ultrasound (US):

a Transcutaneous

b Endosonography

8. Computed tomography (CT)

9. Magnetic resonance imaging (MRI)

10. Angiography

11. Radionuclide imaging:

a Inflammatory bowel disease

b Gastro-oesophageal reflux

c Gastric emptying

d Bile reflux study

e Meckel’s scan

f Gastrointestinal bleeding.

Further reading

Ambrosini R., Barchiesi A., Di Mizio V., et al. Inflammatory chronic disease of the colon: how to image. Eur. J. Radiol.. 2007;61(3):442-448.

Brochwicz-Lewinski M.J., Paterson-Brown S., Murchison J.T. Small bowel obstruction the water soluble follow-through revisited. Clin. Radiol.. 2003;58(5):393-397.

Gasparaitis A.E., MacEneaney P. Enteroclysis and computed tomography enteroclysis. Gastroenterol. Clin. North Am.. 2002;31(3):715-730.

Introduction to Contrast Media

BARIUM

Barium suspension is made up from pure barium sulphate. (Barium carbonate is poisonous.) The particles of barium must be small (0.1–3 µm), since this makes them more stable in suspension. A non-ionic suspension medium is used, for otherwise the barium particles would aggregate into clumps. The resulting solution has a pH of 5.3, which makes it stable in gastric acid.

There are many varieties of barium suspensions in use. Exact formulations are secret. In most situations the preparation will be diluted with water to give a lower density (Table 3.1).

Table 3.1 Barium suspensions and dilutions with water to give a lower density

Proprietary name	Density (w/v) – use
Baritop 100	100% – all parts gastrointestinal tract
EPI-C	150% – large bowel
E-Z-Cat	1–2% – computed tomography of gastrointestinal tract
E-Z HD	250% – oesophagus, stomach and duodenum
E-Z Paque	100% – small intestine
Micropaque DC	100% – oesophagus, stomach and duodenum
Micropaque liquid	100% – small and large bowel
Micropaque powder	76% – small and large bowel
Polibar	115% – large bowel
Polibar rapid	100% – large bowel

Examinations of different parts of the gastrointestinal tract require barium preparations with differing properties:

1. Barium swallow, e.g. E-Z HD 200–250% 100 ml (or more, as required).

2. Barium meal, e.g. E-Z HD 250% w/v. A high-density, low-viscosity barium is required for a double-contrast barium meal to give a good thin coating that is still sufficiently dense to give satisfactory opacification. E-Z HD fulfils these requirements. It also contains simethicone (an anti-foaming and coating agent) and sorbitol (a coating agent).

3. Barium follow-through, e.g. E-Z Paque 60–100% w/v 300 ml (150 ml if performed after a barium meal). This preparation contains sorbitol, which produces an osmotic hurrying and is partially resistant to flocculation.

4. Small bowel enema, e.g. two tubs of E-Z Paque made up to 1500 ml (60% w/v). N.B. As the transit time through the small bowel is relatively short in this investigation, there is a reduced chance of flocculation. This enables the use of barium preparations which are not flocculation-resistant. Some advocate the addition of Gastrografin to the mixture as this may help reduce the transit time still further.

5. Barium enema, e.g. Polibar 115% w/v 500 ml (or more, as required).

Advantages

1. The main advantage when compared to water-soluble contrast agents is the excellent coating which can be achieved with barium, allowing the demonstration of normal and abnormal mucosal patterns.

Disadvantages

1. Subsequent abdominal CT and US are rendered difficult (if not impossible) to interpret. Patients may be asked to wait for up to 2 weeks to allow satisfactory clearance of the barium. If also required, it is advised that the CT and/or US be performed before the barium study.

2. High morbidity associated with barium in the peritoneal cavity.

Complications

1. Perforation. The escape of barium into the peritoneal cavity is rare. If large amounts enter the peritoneal spaces it is extremely serious, and will produce pain and severe hypovolaemic shock. Despite treatment, which should consist of intravenous (i.v.) fluids, steroids and antibiotics, there is still a 50% mortality rate. Of those that survive, 30% will develop peritoneal adhesions and granulomata. Intramediastinal barium also has a significant mortality rate. It is, therefore, imperative that a water-soluble contrast medium is used for any investigation in which there is a risk of perforation, or in which perforation is already suspected.

2. Aspiration. Barium if aspirated is relatively harmless. Sequelae include pneumonitis and granuloma formation. Physiotherapy is the only treatment required (for both aspirated barium and low osmolar contrast material (LOCM)), and should be arranged before the patient leaves hospital.

3. Intravasation. This may result in a barium pulmonary embolus, which carries a mortality of 80%.

For further complications (e.g. constipation and impaction), see the specific procedure involved.

Further reading

Karanikas I.D., Kakoulidis D.D., Gouvas Z.T., et al. Barium peritonitis: a rare complication of upper gastrointestinal contrast investigation. Postgrad. Med. J.. 1997;73:297-298.

Water-Soluble Contrast Agents

GASES

1. Oesophagus, stomach and duodenum – Carbon dioxide and, less often, air are used in conjunction with barium to achieve a ‘double contrast’ effect. For the upper gastrointestinal tract, CO₂ is administered orally in the form of gas producing granules/powder.

The requirements of these agents are as follows:

a Production of an adequate volume of gas – 200–400 ml

b Non-interference with barium coating

c No bubble production

d Rapid dissolution, leaving no residue

e Easily swallowed

Carbex granules and fluid satisfy most of these requirements, but have the disadvantage of being relatively costly.

2. Large bowel – For the large bowel, room air is administered per rectum via a hand pump attached to the enema tube. Carbon dioxide is said to cause less abdominal pain, but inferior bowel distension when compared to air.¹

1 Holemans J.A., Matson M.B., Hughes J.A., et al. A comparison of air, carbon dioxide and air/carbon dioxide mixture as insufflation agents for double contrast barium enema. Eur. Radiol.. 1998;8:274-276.

Further reading

Gellett L.R., Farrow R., Bloor C., et al. Pain after small bowel meal and pneumocolon: a randomized controlled trial of carbon dioxide versus air insufflation. Clin. Radiol.. 1999;54:381-383.

Pharmacological Agents

Glucagon

This polypeptide hormone produced by the alpha cells of the islets of Langerhans in the pancreas has a predominantly hyperglycaemic effect but also causes smooth muscle relaxation.

Adult dose

0.3 mg i.v. for barium meal

1.0 mg i.v. for barium enema.

Advantages

1. It is a more potent smooth muscle relaxant than Buscopan

2. Short duration of action (approx. 15 min)

3. It does not interfere with the small-bowel transit time.

Disadvantages

1. Hypersensitivity reactions are possible, as it is a protein molecule

2. Relatively long onset of action (1 min)

Contraindications

1. Phaeochromocytoma. Glucagon can cause the tumour to release catecholamines, resulting in sudden and marked hypertension; 5–10 mg phentolamine mesilate may be administered i.v. in an attempt to control the blood pressure.

2. Caution is advised in the following conditions:¹

a Insulinoma: an initial increase in blood glucose may be followed by severe hypoglycaemia

Side-effects

1. Nausea and vomiting

2. Abdominal pain

3. Hypokalaemia

5. Rarely hypersensitivity reactions.

1 British National Formulary. 2007;54.

General points

In all barium work a high-kV technique is used (90–110 kV).

As in all radiological procedures, the ALARP (As Low As Reasonably Practicable) principle should be adhered to.

As regards women of child-bearing age, the ‘10-day rule’ is generally applied for both upper and lower gastrointestinal investigations.

Barium has superior contrast qualities and, unless there are specific contraindications, its use (rather than water-soluble agents) is preferred. The barium swallow is often done in conjunction with a barium meal.

CONTRAST SWALLOW

Indications – suspected oesophageal pathology

4. Assessment of tracheo-oesophageal fistulae

5. Assessment of the site of perforation.

Contraindications

Contrast medium

1. E-Z HD 200–250% 100 ml (or more, as required)

2. Iodide-based contrast agent if perforation is suspected (e.g. Conray, Gastrografin)

3. LOCM (approx. 300 mg I ml⁻¹).

1. Gastrografin should NOT be used for the investigation of a tracheo-oesophageal fistula or when aspiration is a possibility.

2. Barium should NOT be used if perforation is suspected.

Equipment

Rapid serial radiography (6 frames per s) or video recording may be required for assessment of the laryngopharynx and upper oesophagus during deglutition.

Patient preparation

None (but as for barium meal if the stomach is also to be examined – see p. 57).

Preliminary film

A control film is advised prior to a water-soluble study if perforation is suspected.

Technique

1. The patient is in the erect, right anterior oblique (RAO) position to throw the oesophagus clear of the spine. An ample mouthful of barium is swallowed, and spot films of the upper and lower oesophagus are taken. Oesophageal varices are better seen in the prone, right posterior oblique (RPO) position, as they will be more distended.

2. If rapid serial radiography is required, it may be performed in the right anterior oblique (RAO) and posterior anterior (PA) positions.

Modification of technique

To demonstrate a tracheo-oesophageal fistula in infants, a ‘pull back’ nasogastric tube oeosophogram may be performed. A nasogastric tube is introduced to the level of the mid-oesophagus, and the contrast agent (barium or LOCM) is syringed in to distend the oesophagus. This will force the contrast medium through any small fistula which may be present. It is important to take radiographs in the lateral projection during simultaneous injection of the contrast medium and withdrawal of the tube. Although some authors recommend that the infant be examined in the prone position whilst lying on the footstep of a vertical tilting table, satisfactory results are possible with children on their side on a horizontal table. It is important to watch for any possibility of aspiration into the airway from overspill. Overspill may lead to the incorrect diagnosis of tracheo-oesophageal fistula if it is not possible to determine whether contrast medium in the bronchi is due to a small fistula which is difficult to see or to aspiration.

Recently, it has been proposed that pull-back studies are not necessary in the majority of children, as tracheo-oesophageal fistulas can usually be demonstrated on standard contrast swallow examination, providing the oesophagus is distended well with contrast media.¹ Pull-back studies are still necessary for intubated patients, or those who are at high risk of aspiration. It is important to remember that fistulas are usually quite high, and the orifice can be occluded by an endotracheal tube. This can prevent the fistula being opacified. This can be rectified by altering the patients position, or slightly withdrawing the ET tube.

Aftercare

Complications

1. Leakage of barium from an unsuspected perforation

1 Laffan E.E., Daneman A., Ein S.H., et al. Tracheoesophageal fistula without esophageal atresia: are pull-back tube esophagograms needed for diagnosis. Pediatr. Radiol.. 2006;36:1141-1147.

Barium Meal

Methods

1. Double contrast – the method of choice to demonstrate mucosal pattern.

2. Single contrast – uses:

a children – since it usually is not necessary to demonstrate mucosal pattern

b to demonstrate gross pathology only.

Indications

1. Failed upper gastrointestinal endosocpy

4. Upper abdominal mass

5. Gastrointestinal haemorrhage (or unexplained iron-deficiency anaemia)

6. Partial obstruction

7. Assessment of site of perforation – it is essential that a water-soluble contrast medium, e.g. Gastrografin or LOCM, is used.

Contraindications

Complete large-bowel obstruction.

Contrast medium

1. E-Z HD 250% w/v 135 ml

2. Carbex granules (double contrast technique).

Patient preparation

1. Nil orally for 6 h prior to the examination

2. It should be ensured that there are no contraindications to the pharmacological agents used.

Preliminary film

Technique

The double contrast method (Fig. 3.1):

1. A gas-producing agent is swallowed.

2. The patient then drinks the barium while lying on the left side, supported by the elbow. This position prevents the barium from reaching the duodenum too quickly and so obscuring the greater curve of the stomach.

3. The patient then lies supine and slightly on the right side, to bring the barium up against the gastro-oesophageal junction. This manoeuvre is screened to check for reflux, which may be revealed by asking the patient to cough or to swallow water while in this position. The significance of reflux produced by tipping the patient’s head down is debatable, as this is an unphysiological position. If reflux is observed, spot films are taken to record the level to which it ascends.

4. An i.v. injection of a smooth muscle relaxant (Buscopan 20 mg or glucagon 0.3 mg) is given. The administration of Buscopan has been shown not to affect the detection of gastro-oesophageal reflux or hiatus hernia.

5. The patient is asked to roll onto the right side and then quickly over in a complete circle, to finish in an RAO position. This roll is performed to coat the gastric mucosa with barium. Good coating has been achieved if the areae gastricae in the antrum are visible.

Figure 3.1 Barium meal sequence. Please note in a, b, c and d, the patient position is depicted as if the operator were standing at the end of the screening table looking towards the patient’s head. = Barium

Films

There is a great variation in views recommended, and the following is only the scheme used in our departments. In some departments fewer films are taken to reduce the cost and radiation dose:

1. Spot films of the stomach (lying):

a RAO – to demonstrate the antrum and greater curve

b Supine – to demonstrate the antrum and body

c LAO – to demonstrate the lesser curve en face

d Left lateral tilted, head up 45° – to demonstrate the fundus.

From the left lateral position the patient returns to a supine position and then rolls onto the left side and over into a prone position. This sequence of movements is required to avoid barium flooding into the duodenal loop, which would occur if the patient were to roll onto the right side to achieve a prone position.

2. Spot film of the duodenal loop (lying):

a Prone – the patient lies on a compression pad to prevent barium from flooding into the duodenum.

An additional view to demonstrate the anterior wall of the duodenal loop may be taken in an RAO position.

3. Spot films of the duodenal cap (lying):

b RAO – the patient attains this position from the prone position by rolling first onto the left side, for the reasons mentioned above

4. Additional views of the fundus in an erect position may be taken at this stage, if there is suspicion of a fundal lesion.

5. Spot films of the oesophagus are taken, while barium is being swallowed, to complete the examination.

Modification of technique for young children

The main indication will be to identify a cause for vomiting. The examination is modified to identify the three major causes of vomiting – gastro-oesophageal reflux, pyloric obstruction and malrotation, and it is essential that the position of the duodeno-jejunal flexure is demonstrated:

1. Single contrast technique using 30% w/v barium sulphate and no paralytic agent.

2. A relatively small volume of barium – enough to just fill the fundus – is given to the infant in the supine position. A film of the distended oesophagus is exposed.

3. The child is turned semi-prone into a LPO or RAO position. A film is exposed as barium passes through the pylorus. The pylorus is shown to even better advantage if 20–40° caudocranial angulation can be employed with an overhead screening unit. Gastric emptying is prolonged if the child is upset. A dummy coated with glycerine is a useful pacifier.

4. Once barium enters the duodenum, the infant is returned to the supine position, and with the child perfectly straight a second film is exposed as barium passes around the duodenojejunal flexure.

5. Once malrotation has been diagnosed or excluded, a further volume of barium is administered until the stomach is reasonably full and barium lies against the gastro-oesophageal junction. The child is gently rotated through 180° in an attempt to elicit gastro-oesophageal reflux.

In newborn infants with upper intestinal obstruction, e.g. duodenal atresia, the diagnosis may be confirmed if 20 ml of air is injected down the nasogastric tube (which will almost certainly have already been introduced by the medical staff). If the diagnosis remains in doubt, it can be replaced by a positive contrast agent (dilute barium or LOCM if the risk of aspiration is high).

Aftercare

1. The patient should be warned that his bowel motions will be white for a few days after the examination and may be difficult to flush away.

2. The patient should be advised to eat and drink normally to avoid barium impaction. Laxatives may be taken if required.

3. The patient must not leave the department until any blurring of vision produced by the Buscopan has resolved.

Complications

1. Leakage of barium from an unsuspected perforation

2. Aspiration of stomach contents due to the Buscopan

3. Conversion of a partial large bowel obstruction into a complete obstruction by the impaction of barium

4. Barium appendicitis, if barium impacts in the appendix (exceedingly rare)

5. Side-effects of the pharmacological agents used.

N.B. It must be emphasized that there are many variations in technique, according to individual preference, and that the best way of becoming familiar with the sequence of positioning is actually to perform the procedure oneself.

BARIUM FOLLOW-THROUGH

Methods

1. Single contrast

2. With the addition of an effervescent agent

3. With the addition of a pneumocolon technique.

Indications

3. Anaemia/gastrointestinal bleeding

4. Partial obstruction

5. Malabsorption

6. Abdominal mass.

Contraindications

1. Complete obstruction. This may not be an absolute contraindication if the surgical team are aware of this.

2. Suspected perforation (unless a water-soluble contrast medium is used).

Contrast medium

E-Z Paque 100% w/v 300 ml usually given in 10–15-min increments, although some radiologists give the full 300 ml at once. The transit time through the small bowel has been shown to be reduced by the addition of 10 ml of Gastrografin to the barium. In children, 3–4 ml kg⁻¹ is a suitable volume.

In situations where barium is contraindicated, non-ionic water-soluble solutions have been shown to be a satisfactory alternative.¹

Patient preparation

Metoclopramide 20 mg orally may be given before or during the examination.

Preliminary film

Plain abdominal film is used if small bowel obstruction is thought possible.

Technique

The aim is to deliver a single column of barium into the small bowel. This is achieved by laying the patient on his right side after the barium has been ingested. Metoclopramide enhances the rate of gastric emptying. If the transit time through the small bowel is found to be slow, the addition of an osmotic water-soluble contrast agent may help to speed it up. If a follow-through examination is combined with a barium meal, glucagon is used for the duodenal cap views rather than Buscopan because it has a short length of action and does not interfere with the small-bowel transit time.

Films

1. Prone PA films of the abdomen are taken every 15–20 min during the first hour, and subsequently every 20–30 min until the colon is reached. The prone position is used because the pressure on the abdomen helps to separate the loops of small bowel.

2. Spot films of the terminal ileum are taken supine, using a compression pad.

Aftercare

As for barium meal.

Complications

As for barium meal.

1 Jobling C., Halligan S., Bartram C. The use of water-soluble contrast agents for small bowel follow-through examinations. Eur. Radiol.. 1999;9:706-710.

Further reading

Ha H.K., Shin J.H., Rha S.E., et al. Modified small bowel follow through: use of methylcellulose to improve bowel transradiance and prepare barium suspension. Radiology. 1999;211:197-201.

Summers D.S., Roger M.D., Allan P.L., et al. Accelerating the transit time of barium sulphate suspensions in small bowel examinations. Eur. J. Radiol.. 2007;62(1):122-125.

Small-Bowel Enema

Advantage

This procedure gives better visualization of the proximal small bowel than that achieved by a barium follow-through because rapid infusion of a large, continuous column of contrast medium directly into the jejunum provides better distension of the proximal small bowel. This is less effective in the ileum.

Disadvantages

1. Intubation may be unpleasant for the patient, and may occasionally prove difficult.

2. It is more time-consuming for the radiologist.

3. There is a higher radiation dose to the patient (screening the tube into position).

Indications and Contraindications

These are the same as for a barium follow-through. In some departments it is only performed in the case of an equivocal follow-through.

Contrast medium

1. E-Z Paque 70% w/v diluted

2. Dilute Baritop

3. 600 ml of 0.5% methylcellulose after 500 ml of 70% w/v barium.¹

It may be difficult to obtain good distension and double-contrast effect of the distal small bowel and terminal ileum.

Equipment

A choice of tubes is available:

1. Bilbao-Dotter tube with a guidewire (the tube is longer than the wire so that there is reduced risk of perforation when introducing the wire).

2. Silk tube (E. Merck Ltd). This is a 10-F, 140-cm long tube. It is made of polyurethane and the stylet and the internal lumen of the tube are coated with a water-activated lubricant to facilitate the smooth removal of the stylet after insertion.

Patient preparation

1. NBM after midnight

2. If the patient is taking any antispasmodic drugs, they must be stopped 1 day prior to the examination

3. Tetracaine lozenge 30 mg, 30 min before the examination.

Immediately before the examination the pharynx is anaesthetized with lidocaine spray.

Preliminary film

Plain abdominal film is used if a small bowel obstruction is suspected.

Technique

1. The patient sits on the edge of the X-ray table. The pharynx is thoroughly anaesthetized with lidocaine spray. If a per nasal approach is planned, the patency of the nasal passages is checked by asking the patient to sniff with one nostril occluded. The silk tube should be passed with the guidewire pre-lubricated and fully within the tube, whereas for the Bilbao-Dotter tube it may be more comfortable to introduce the guidewire after the tube tip is in the stomach.

2. The tube is then passed through the nose or the mouth, and brief lateral screening of the neck may be helpful in negotiating the epiglottic region. The patient is asked to swallow with the neck flexed, as the tube is passed through the pharynx. The tube is then advanced into the gastric antrum.

3. The patient then lies down and the tube is passed into the duodenum. Various manoeuvres may be used alone or in combination, to help this part of the procedure, which may be difficult:

a Lay the patient on his left side so that the gastric air bubble rises to the antrum, thus straightening out the stomach.

b Advance the tube whilst applying clockwise rotational motion (as viewed from the head of the patient looking towards the feet).

c In the case of the Bilbao-Dotter tube, introduce the guidewire.

d Get the patient to sit up, to try to overcome the tendency of the tube to coil in the fundus of the stomach.

e Metoclopramide (20 mg i.v.) may help.

4. When the tip of the tube has been passed through the pylorus, the guidewire tip is maintained at the pylorus as the tube is passed over it along the duodenum to the level of the ligament of Treitz. Clockwise torque applied to the tube may again help in getting past the junction of the first and second parts of the duodenum. The tube is passed beyond the duodenojejunal flexure to diminish the risk of aspiration due to reflux of barium into the stomach.

Buy Membership for Radiology Category to continue reading. Learn more here

Related

A Guide to Radiological Procedures