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Chapter 17 (page 81)
Ultrasonography of Pyloric Motility and Gastric Emptying
Bateman et al (l977) measured the rate of gastric contractions by means of ultrasound
pulse-echo scanning. As the procedure was non-invasive, non-ionizing and non-
traumatic, it had certain advantages over other modes of examination. After an overnight
fast normal subjects seated in the upright position imbibed 500 ml orange cordial warmed
to 37ºC. Using a standard, commercially available B-scanner with a 1.5 MHz
probe, the fluid in the stomach presented as an echo-free, transonic region. A
quantitative display of the movement of the anterior and posterior walls of the "antrum"
could be obtained in T-M (time motion) mode, and a permanent photographic record
could be made. A continuous A-mode record of the wall movements was obtained
simultaneously on video-tape.
In the normal stomach a biphasic response to the liquid meal was seen. Initially the
"antral" contraction waves were slow and irregular, but after 7 to 15 min they appeared
more frequently at regular 20 second intervals. The temperature of the fluid appeared to
be of importance as gastric contraction waves were found to be inhibited at temperatures
lower than 37ºC. Intravenous administration of 15 mg or 30 mg propantheline
caused cessation of the contractions for periods of up to 3 hours. The method was found
to be particularly suited to the measurement of contraction rates.
Holt et al. (l980) used real-time ultrasonic imaging to study contractions in the pyloric
"antrum" and body of the stomach in 10 healthy subjects after a liquid test meal of 500
ml warmed orange juice. In 5 subjects scanning was also performed at intervals after a
variety of solid and liquid meals. In all cases a real-time ultrasonic scanner containing 4
rotating transducers of 2.5 MHz was used; scans were done with the subject standing or
seated upright. Real-time ultrasonic images were recorded on video-casettes and
permanent photographic records were obtained.
In the resting state the distended, liquid-filled "antrum" was visualized as a rounded,
echo-free or transonic zone. After the liquid meal contraction of the "antrum" was absent
or weak for up to 5 minutes, but this was followed by regular contractions occurring with
a frequency of 3 per minute, i.e. a contraction every 20 seconds; these were taken to be
peristaltic waves. Propantheline 30 mg intravenously abolished the "antral" movements,
while metoclopramide 10 mg intravenously enhanced the magnitude and frequency of the
contractions. It was said that the images produced by real-time ultrasonic techniques
closely resembled those seen during barium screening studies.
King et al. (l984) examined l7 normal subjects using a rotating transducer real-time
ultrasound scanner with a 5 MHz probe. Subjects were examined seated in the upright
position after an overnight fast and after imbibing 500 ml warmed orange cordial to
which 0.5 g of chopped and sieved bran was added. The bran particles suspended in the
fluid luminal contents acted as a sonic marker, thus allowing identification of movement
through the pylorus. Forward flow indicated movement of particles from the stomach to
the duodenum and retrograde flow movement from the duodenum into the stomach.
Images of the bran particles, the "distal or terminal antrum", pylorus and duodenum were
obtained. (Comment: The "terminal antrum" was defined as the immediate
prepyloric area. More detailed definitions of the terms "antrum" and "terminal antrum"
were not given.) The timing and duration of the terminal antral contractions (TACs),
proximal duodenal contractions, and periods of forward and retrograde flow through the
pylorus in each individual were then compared in order to establish the relationships
between them. The duration of a terminal antral contraction was about 4 seconds (mean
3.93 seconds ± 0.8). Pyloric closure invariably occurred as the gastric peristaltic
wave reached the pylorus at the midpoint of the terminal antral contraction. Contractions
of the first part of the duodenum were seen to occur just after the midpoint of the
majority (86 percent) of terminal antral contractions. The vast majority (92 percent) of
duodenal contractions occurred immediately after the terminal antral contraction, 5.5
percent occurred simultaneously with it and 2.5 percent were ectopic. Contraction of the
first part of the duodenum lasted about 5 seconds (mean 4.93 seconds SD ± 1.75).
Transpyloric fluid movement was reflected by the movement of the bran particles. It
occurred as brief episodes when the pylorus was open. Forward flow occurred in 81
percent of the cycles of contraction and lasted about 2 to 4 seconds. The majority of
these episodes occurred after relaxation of the terminal antrum, pylorus and duodenum,
while 25 percent occurred just before the terminal antral contraction. The discrete
episodes of forward flow thus occurred as the terminal antrum, pylorus and duodenum
were relaxed at the end or the start or each peristaltic cycle. Occasionally there was no
forward flow in spite of terminal antral and duodenal contractions.
Retrograde flow, in episodes lasting up to 5 seconds, occurred in the vast majority of
observed cycles of contraction. Most of these episodes were seen just before the terminal
antral contraction, with 39 percent following it. A brief period of forward flow often
ended abruptly and was sometimes immediately followed by a period of retrograde flow.
Bolondi et al. (l985) measured gastric emptying times in l8 normal subjects and 36
patients with functional dyspepsia, using a high-resolution real-time scanner with a 3.5
MHz linear array transducer. Having measured the transverse diameter and length of the
"antrum" before and after a mixed solid-liquid meal, the volume of the "antropyloric"
region was calculated and the time taken for its emptying determined. The antrum was
taken to be the area extending from the "angle region" to the pylorus. Significantly
longer emptying times were observed in patients with functional dyspepsia as compared
with normal subjects. It was stated that various phases of antral peristalsis, such as
propulsion waves, grinding movements and retropulsion could be studied by means of
ultrasonic techniques, but no further particulars of these movements were given.
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