Gastroesophageal
reflux disease (GERD) is a disorder in which the contents of the
stomach regurgitate back up into the esophagus. The squamous
epithelial lining of the esophagus is not protected by a mucus
secretion in the same way the stomach lining is and the refluxed
acidic contents of the stomach cause a burning sensation often
referred to as "heartburn". Over a prolonged period of time,
the refluxed stomach acid can cause inflammatory esophagitis and
ulcerative damage to the lower esophagus. Dysphagia, esophageal
stricture, bleeding and the development of Barrett's esophagus are
other complications of longstanding reflux. In extreme cases, the
stomach contents may reflux back so far that it is inhaled into the
bronchi and lungs. A pneumonitis can result. The vocal chords may also
be damaged in severe cases of reflux.
Although reflux
(spitting up) is normal in infants up to about 8 or 9 months of age
because their lower esophageal sphincters (LES) are not yet fully
developed, nocturnal aspiration of refluxed stomach contents is of
particular concern and importance. Clinically significant reflux can
result in malnutrition, strictures, recurrent pneumonia and even
death.
The lower
esophageal sphincter (LES) is responsible for controlling the passage
of food from the esophagus into the stomach and for preventing the
reflux of stomach contents back up into the esophagus. Failure of the
LES to function effectively can lead to GERD. In most cases, the
reason for LES incompetence is idiopathic but it can also be due to
disorders such as
scleroderma.
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The determination
and quantitation of gastroesophageal reflux in nuclear medicine is
based upon providing the patient with a radioactively labelled,
acidic, liquid drink that will readily reflux in a patient predisposed
to reflux. After the patient ingests the drink, the level of activity
determined to be refluxing back into the esophagus is calculated as a
percent of the total activity in the stomach. Techniques used to
increase the sensitivity of the procedure include:
- a high acidity
radiopharmaceutical solution;
- imaging the
patient in a supine position;
- applying an
abdominal binder to increase intra-abdominal pressure.
The nuclear
medicine gastroesophageal imaging and function study has several
significant advantages compared to other tests:
- it is relatively
accurate and sensitive;
- it is
quantitative;
- the
radiopharmaceutical gives a physiological response;
- it is
technically easy to perform;
- it is
non-invasive;
- the radiation
dose to the patient is fairly low.
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A gastroesophageal
reflux imaging and function study is indicated for the evaluation of
patients with symptoms of reflux including:
- persistent,
recurrent heartburn (the most common symptom);
- esophagitis;
- regurgation of
stomach contents into the mouth;
- chest pain that
has been determined not to be cardiac in origin;
- dysphagia;
- nocturnal
aspiration (primarily in children);
- evaluation of
therapy for reflux.
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Patient Preparation
Adult patients
should be fasting for at least 8 hours and should be off any
promotility medications for at least 48 hours. Prior to ingesting the
radiopharmaceutical solution (see below) the patient is fitted with a
large abdominal binder that has a balloon device that can be inflated
like a blood pressure cuff to apply pressure to the abdomen. The
binder must be placed below the ribs to avoid fracture and to apply
upward pressure on the stomach.
Infants and young
children should have fasted for at least 2 hours prior to the
procedure. The abdominal binder is not used on infants and children.
The test procedure
is explained to the patient.
Pharmacological
Interventions
No specific
pharmacological interventional techniques are commonly used with this
study.
Radiopharmaceuticals
For adults, 10 to
15 MBq of Tc-99m sulfur colloid is added to a solution of 150 mL of
orange juice and 150 mL of 0.1N hydrochloric acid (HCl). The solution
is administered orally. Once the labelled solution has been ingested,
25 to 30 mL of water may be given to rinse the activity from the
esophagus. Imaging should begin within 10 minutes of administration of
the Tc-99m sulfur colloid solution.
For infants and
children, 5 to 10 MBq of Tc-99m sulfur colloid is administered orally
with milk, formula or juice. The activity concentration should be
about 0.20 MBq/mL. If the procedure is being preformed to investigate
overnight aspiration of refluxed stomach contents, the activity used
should be increased to about 30 to 40 MBq to compensate for decay.
Once the radiopharmaceutical has been ingested, about 10 to 20 mL of
unlabelled fluid should be administered to wash activity from the
mouth and esophagus. A pacifier given to an infant will stimulate dry
swallowing which will help ensure complete initial transit of the
radiolabel.
Equipment
A LFOV gamma camera
with a low energy, all purpose collimator interfaced to a nuclear
medicine computer system is preferred. The camera's analyzer is set at
140 keV with a 15% to 20% window. The computer acquisition uses a 64 x
64 x byte matrix.
Image / Data
Acquisition Parameters
Adult Procedure
After ingesting the
radiolabelled acidic solution, a single, upright image is acquired for
30 to 60 sec to visually ensure that the activity has cleared from the
esophagus. Should some residual activity remain in the lower
esophagus, 25 to 30 mL of water may be given to flush the activity
through. With certain disorders such as severe achalasia or esophageal
diverticula, the activity may not completely clear and baseline
quantitative data must be obtained for subtraction from subsequent
values. This is discussed further below.
Following the
upright image, the patient is centred supine within the field of view
with the stomach located toward the bottom but fully included. An
initial 30 to 60 second acquisition is performed with no pressure on
the binder. Following this, a series of 30 to 60 sec images are
obtained at sphygmomanometer pressure readings of 20, 40, 60, 80, and
100 mmHg. The binder is not deflated between images.
Regions of Interest
(ROI's) are drawn around the esophagus on the image acquired at each
pressure value and the counts within each are determined (Ep). If
there was any residual activity not cleared from the lower esophagus,
an ROI is drawn around the esophagus on the initial upright image and
the counts are used as a backgroung correction (Eb). The total initial
counts in the stomach are determined from an ROI drawn around the
stomach in the initial upright or the 0 mmHg pressure image (G0).
The
gastroesophageal reflux is calculated with the following formula:
%R = (Ep - Eb) / G0
x 100
Pediatric Procedure
After ingestion of
the radiolabelled milk, formula or juice the patient is centred supine
within the field of view with the stomach located toward the bottom
but fully included and the mouth included at the top.
The gamma camera is
set to acquire 1 image per minute for 60 minutes. The intensity
setting on the mulit-formatter is adjusted to high to allow
visualization of small amounts of reflux. The computer is set to
acquire serial 10 second images for 60 minutes. At the end of the
hour, anterior and posterior static images of the lungs are taken for
about 3 to 5 minutes each. These high count images are intended to
show any evidence of aspiration. The anterior and posterior static
images are repeated at 2 hours for about 3 to 5 minutes each (same
time as above) and again at 24 hours for about 6 to 10 minutes (double
the time used above) to once again look for evidence of aspiration.
High multi-formatter intensity settings are used.
Reflux is
calculated using the same equation used for adults.
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In adults, normal
levels of reflux should be less than about 4% at all levels of binder
pressure.
In one study, a
group of patients with confirned GERD had %Reflux values in the range
of about 10 to 15%.
In pediatrics,
reflux may be calculated as for the adult but since a low level of
reflux is often normal in an infant, a more significant finding is
repeated episodes of reflux during the study. These are generally
visible on the images taken with a high intensity multiformatter
setting. Evidence of activity in the lungs is diagnostic of pulmonary
aspiration.
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Acid Perfusion Test
Endoscopy
Upper
Endoscopy
Barium Upper
Gastrointestinal Study
Upper
GI Series (Barium Swallow)
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Pathology
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