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What is the contribution of scintigraphy in gastroesophageal reflux in children
C. Maurage, F. Baulieu, N. Faure, K. Dieckmann, J.C. Rolland (Tours)
Supplementary investigations for gastroesophageal reflux in children
The physician who looks after a child with suspected gastroesophageal reflux (GER) must answer various questions:
- Is there genuine and abnormal GER?
- What is the cause (or mechanism)?
- How often, how much, how long and how acid is the reflux into the esophagus?
- Is there any esophagitis?
- Is there any aspiration into the bronchi/lungs?
- Finally, did the GER disappear after treatment?
Each of the various investigations available to supplement the clinical findings offers a different contribution to these questions.
Barium transit through the esophagus, stomach and duodenum
This remains the most readily available and easiest investigation to establish the existence of reflux, and in particular it is the only one for proper examination of the anatomy of the region of the esophagus/cardia. Nevertheless, there are various problems with clinically-doubtful cases. These include difficulties in standardizing the investigation (volume, positions, etc.) and difficulties in interpretation, and, in particular, some lack of sensitivity in both confirmation of intermittent reflux (not occurring at the time of the investigation) as well as in the detection of esophagitis. Exposure to irradiation depends largely on the equipment and on the number of films taken. The cost (Z120), which is not negligible, is often ignored.
Esophagoscopy
The main and specific purpose of this is to visualize any esophagitis and to confirm it by histology of a biopsy (an invasive procedure which is reasonably well tolerated). A general anaesthetic is sometimes required. Cost: K50.
Esophageal manometry
This more recent and less widespread investigation is a technique for examining normal esophageal function and the various mechanisms involved in its abnormalities
rather than a method for diagnosing reflux. (It only detects pressure changes and cannot, strictly speaking, confirm reflux). Cost: K20.
Measurement of pH in the esophagus
This is carried out continuously with miniature electrodes over 12 or 24 h; it is very reliable, sensitive and safe.
The disadvantages are the length of recording, the unpleasantness of having tubes in place and, in small children, the difficulty of establishing an intrabuccal reference electrode.
It is an excellent method for detecting very small or late reflux and for defining the rate, amount and duration of reflux, but it is only a test of acid reflux at a restricted level in the esophagus (the site of the lower end of the catheter). The cost varies with technique and duration (in the clinic: K40).
Scintigraphy
This is less-widely used for the diagnosis of GER in children.
The inherent qualities of a radioisotope test (sensitivity, scanty irradiation which is not influenced by the number of films or the length of the investigation, the ability to carry out kinetic and quantitative analyses) make it a priori very suitable for the study of GER and for looking for possible inhalation into the lungs.
We thought it would be helpful to draw up a protocol and to carry out the test in children. As a result, we have learned something of the practical problems involved in its performance and interpretation, and we can discuss its place among other available methods on the basis of personal experience.
The technique involves labeling a meal with 0.5 mCi of 99mTc colloidal sulfide. An aliquot of the meal is mixed with colloidal technetium. The rest is taken without any radioactive product and has the effect of washing residual activity out of the esophagus. Subsequently, recording is continued for 1 h with 60 images being taken at intervals of 1 min. Later images are taken from several directions (anterior, posterior, right and left lateral) 4 and 24 h after the meal. The recordings from an investigation can then be used for kinetic and quantitative studies (activity curves over the course of time in selected areas of interest - quantification).
In children with reflux confirmed by barium studies or pH measurement the images on scintigraphy, and the activity curves show one, two or more bouts of reflux. Sometimes a focus can be seen outside the esophagus which gives rise to a suspicion of aspiration into the lungs.
Discussion
Arrangement of this protocol and the results of two recent studies in children with respiratory symptoms have allowed the advantages and disadvantages of this
technique to be confirmed and defined, as well as uncovered certain problems with interpretation.
Advantages
Some of the advantages are linked to the protocol employed. There is little inconvenience for the child who does not have to undergo anesthesia, premedication, additional fasting, passage of tubes or intravenous injection. The product is given with a normal meal and the test is carried out in as physiological manner as possible.
Irradiation is scanty. The dose of 500 µCi delivers a mean 100 mrads to the whole body which is clearly less than a series of X-rays during a barium investigation.
There are other advantages associated with isotope technology:
- Sensitivity. One of the aims of this study was to measure this and define its limits. However, it is already clear from the nature of the findings that very small refluxes of the isotope can be detected but this raises the problem of their pathological significance.
- Measurement of activity at intervals of time and in predefined areas enables an objective study of the rate, amount and duration of reflux (esophageal clearance) and gastric emptying. These last two parameters appear to be particularly closely-associated with the pathological nature of the reflux. This ability to quantify the results also means that comparative tests could be envisaged, especially of the effects of different symptomatic and curative forms of treatment.
- Finally, scintigraphy has the specific advantage of allowing detection of aspiration of fluid from the stomach into the bronchi and lungs. The significance of such reflux aspirations in the pathogenesis of certain asthma-like syndromes and repeated bronchopneumonias in infants and children is now well understood.
Disadvantages
As shown previously these are scanty for the child; however, they are important to the medical team, though they are not unique to scintigraphy. The disadvantages are the problems involved in transporting the child to the department where examinations are to be carried out, and in accompanying the child during the examinations (4-5 h). The cost, Z150 + ERA154, is relatively high but should be kept in proportion (by comparison with barium studies).
Problems of interpretation
Two problems have arisen: the first one is a product of the sensitivity of the technique and takes the form of how much significance to attach, particularly in very young infants, to scanty, small, short bouts of reflux which occur close to meals. Continuous pH measurement poses problems of the same nature but it does not record
reflux which is buffered by a meal.
Because it allows precise, objective and comparable measurements to be taken, it is reasonable to suppose that scintigraphy can make a major contribution to this study and to decisions whether or not GER in children are abnormal.
The other problem is particularly important because it concerns confirmation of aspiration into the lungs which is the specific advantage of scintigraphy over other investigations. When faced with a focus of activity high-up and close to the side of the esophagus, it is sometimes difficult to distinguish between aspiration into the chest and intrabuccal reflux. This difficulty is obviously greater as the dimension becomes smaller in younger children. The solution certainly lies in meticulous pinpointing of the levels and by careful observation of the child with particular attention to changes in the position of its head and any regurgitation which takes place during the investigation.
At this point in our study, we formed an opinion that scintigraphy with technetium sulfide is as interesting as there was reason to suppose in the investigation of GER in children. This study has been continued in a more systematic manner mainly to define the links between respiratory disease and GER [4].
This investigation, therefore, is of interest:
- in clinical circumstances which suggest reflux where barium studies, which are less sensitive, are negative, and facilities for pH measurement are not available;
- when it is desirable to identify the timing, rate, amount and duration of an established GER and its relationship with gastric emptying regardless of the pH;
- as a sensitive supplementary criterion for assessment of a child's response to treatment for GER which is not unpleasant for the child;
- finally, and for this purpose, there is no substitute for scintigraphy for recognition of reflux aspiration, particularly when looking for the etiology of asthma-like dyspnea and recurrent bronchopneumonia in children. The timing should, of course, be chosen on the basis of the clinical circumstances and the results of the more usual investigations (biochemical, radiological, immunological) which are often requested in this context.
Conclusion
Scintigraphy with technetium sulfide has a role in the investigation of GER and its complications in children. In the light of its inherent qualities, it may well be that further study of this method of investigation will improve our understanding of the physiopathology of GER in children and of the extent of its involvement in complex disease processes.
References