Chapter 26 (page 122)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 26 (page 122)

Although all 9 patients with nausea, bloating and vomiting studied by You et al. (l980) had antral arrhythmias, Stoddard et al. (l98l) described 5 patients with antral arrhythmia without any gastrointestinal symptoms at all. In their view the association between antral arrhythmia and disturbed gastric motility remained unclear, although it was possible that such arrhythmia might be associated with delay in gastric emptying.

Hamilton et al. (l986) studied the BER in 20 normal control subjects and in 5 patients with nausea and vomiting of longer than 6 months' duration. All patients had delayed gastric emptying as diagnosed by radionuclide scanning techniques, and 4 had previously been diagnosed as diabetic gastroparesis. The BER was recorded from the abdominal surface by means of a cutaneous electrode, and was shown to be similar in form and frequency to recordings obtained by mucosal suction electrodes. In one normal subject and in 4 of the 5 patients, periods occurred in which BER rates exceeded 5 per minute. In a normal subject the period of tachygastria lasted only 2.5 minutes and the subject remained asymptomatic. In patients, tachygastria lasted for periods of 4 minutes and was associated with nausea; the nausea resolved when the fast rate abated. The fifth patient was asymptomatic during the recording and had no tachygastria. Again it appeared if the recordings were done during periods of nausea and not while retching or vomiting occurred.

Using cutaneous electrodes, Geldof et al. (l986) recorded gastric myoelectrical behaviour by electrogastrography in 48 patients with prolonged, unexplained nausea and vomiting, and in 52 normal control subjects, in the fasting and post-prandial states. In 30 of the 48 patients gastric emptying studies were done, using a radiolabelled solid meal. No mention was made of actual retching or vomiting during the investigations, and it seems if the recordings were done during the phase of nausea. The patient group could be divided into 2 subgroups: in 25 patients all electrogastrographic parameters were identical to the control group, while in 23 abnormal myoelectrical activity was found, characterised by instability of the gastric pacemaker frequency, tachygastrias in both the fasting and postprandial states, and absence of the normal increase in amplitude in the postprandial tracing. This last characteristic was correlated with delayed gastric emptying of solids. Not all patients displayed all three abnormal features; tachygastria lasting between 3 and 14 minutes for instance, was seen in 8 of the patients. It is generally assumed that no motor activity is present during a tachygastria (Telander et al l978; You et al. l980; You and Chey l984; Geldof et al. l986), which is generated in an "antral" ectopic focus and which overrides the normal gastric pacemaker (Telander et al. l978). It was concluded that in a heterogeneous group of patients with unexplained nausea and vomiting, a subgroup could be discerned with abnormal myoelectrical activity which was related to the symptoms.

Kerlin (l989) studied the contractile activity of the stomach and small intestine in 20 patients with longstanding, idiopathic nausea and vomiting, in the fasting and postprandial states. Records were obtained by a low compliance infusion system from the gastric "antrum" (four sites), the duodenum and the jejunum; it appears if the studies were done during the stage of nausea. Only two patients had contractile abnormalities during fasting. After a solid-liquid test meal, the contractility of the gastric "antrum" was significantly impaired in patients as compared with normal controls. It was concluded that postprandial "antral" hypomotility was a major abnormality in patients with unexplained nausea and vomiting.

Retching

The retching phase is characterized by a series of violent spasmodic abdomino-thoracic contractions with the glottis closed. During this time the inspiratory movements of the chest wall and diaphragm are opposed by the expiratory contractions of the abdominal musculature. At the same time movements of the stomach and its contents take place. Whereas a patient will complain of disagreeable sensations during nausea, speech is not possible during retching. The characteristic movements furnish a ready diagnostic sign of the retching phase.

During gastroscopic observations retching usually interferes to such an extent with the examination that it is difficult to observe the motor behaviour of the stomach. Schindler (l937) studied retching on two occasions during gastroscopy and noted that longitudinal folds appeared in the previously smooth "antrum", thickened quickly, came together and completely closed the "antrum". (Comment: The description tallies with contraction of the pyloric sphincteric cylinder during which the folds become longitudinal, so that only longitudinal folds are seen in the fully contracted cylinder) (Chap. 13).

Torgersen (l942) stated that the canalis egestorius (pyloric sphincteric cylinder) contracted during vomiting, and referred to previous work by Groedel who had illustrated the contraction of the two loops and the intervening musculature during vomiting.

Lumsden and Holden (l969) gave a detailed description of the movements of the stomach and duodenum in vomiting as seen in 3 cases during diagnostic radiological investigations. They did not refer to, and did not base their findings on, the concept of the pyloric sphincteric cylinder. In their first case, during retching, a constriction was described and illustrated in the proximal part of the "antrum". The greater curvature in this region showed a deep notch and was closely approximated to the lesser curvature. (Comment: From the description and illustration it is clear that the constriction and deep notch correspond to contraction of the left pyloric loop, with a collection of barium in the pyloric sphincteric cylinder on its aboral side). On an exposure taken immediately afterwards, the prepyloric region had hardly changed. (Comment: In the illustration a collection of barium is seen in the sphincteric cylinder between the right and left pyloric loops). At this stage the body of the stomach had also contracted and barium was being expelled through the cardia.