GERD is a primary motility disorder, mainly caused by reflux of gastric content during TLESRs inducing symptoms. None of the symptoms asso ciated with GER and GERD are specific. Reflux disease can be a primary condition, or it can be the consequence of other abnormalities (such as neurological impairment, cystic fibrosis, pyloric hypertrophy) favoring GER. The long list of differential diagnoses is discussed under the other headings of this chapter, and depends on the age of the patient and the presenting symptom.
Because of lack of space, diagnostic procedures are not discussed in full detail. Detailed information regarding the techniques, indications and pitfalls of radiologic contrast studies, reflux scintiscan-ning, ultrasound, pH metry, endoscopy and manometry can be found in other textbooks or review papers. Interest will be focused on recent developments such as impedancometry. The development of a validated 'infant GERD questionnaire' is likely to be the development in diagnostic accuracy with the greatest impact.
Radiological contrast studies, scintiscanning and ultrasound are techniques evaluating postprandial reflux, and provide some information on gastric emptying. Normal ranges are not well established for any of the three procedures. Regarding gastric emptying, 13-C breath tests are more standardized (but the role of delayed gastric emptying in GER(D) is controversial). Scintiscanning may show pulmonary aspiration, although the sensitivity of the technique is extremely low. Contrast radiology is of importance to rule out anatomic abnormalities such as malrotation, duodenal web, stenosis and achalasia.
There are no age or weight limitations in performing endoscopy. Endoscopy shows anatomic malformations and esophagitis, not reflux. Endoscopy-negative reflux disease is common. Biopsies of duodenal, gastric and esophageal mucosa are mandatory to exclude eosinophilic infiltration.
Ambulatory 24-h esophageal pH monitoring measures the incidence and duration of acid reflux, and should be considered the 'silver standard'. It is the best method to measure the presence of acid in the esophagus, but not all reflux causing symptoms is acid. However, it is likely that the majority of GERD patients suffer acid reflux. Esophageal pH metry is useful in evaluating the effect of any therapeutic intervention on reducing esophageal acid exposure. Since medical treatment currently focuses on reducing gastric acid secretion, the technique offers the possibility of measuring intragastric and esophageal recording of pH simultaneously. Manometry does not demonstrate reflux, but is of interest in showing the pathophysiological mechanisms causing the reflux (by measuring the frequency and duration of TLESRs), and is indicated in specific situations such as achalasia. Ambulatory 24-h esophageal manometry, in combination with pH metry, is now technically feasible. Long-lasting investigations offer the opportunity of measuring events in upright and recumbent positions, awake and asleep. Results of pH monitoring depend on the hardware and the software used.94 The correlation between results obtained with different types of electrodes, glass and antimony, is extremely poor.95
Impedancometry is a technique gaining more and more interest, although it has existed for many years. The technique measures electrical potential differences, and is therefore not pH-dependent. The technique offers the possibility of distinguishing between acid and non-acid reflux (in combination with pH metry), and between liquid and gas reflux. Interpretation of the recording is still quite laborious and necessitates sufficient experience. (This is of course true for any of the investigation techniques.) Impedancometry seems especially of interest in patients with endoscopic and pH metric-negative symptoms suggesting GERD.
Because reflux in infants is common, because there is no 'gold standard' investigation, and because investigations are invasive and expensive, interest has focused on the development of an 'infant GER-questionnaire'.7 Recently, an improved questionnaire was developed.96 The questionnaire offers the advantage of an objective, validated and repeatable quantification of symptoms suggesting GERD, and thus offers the possibility of measuring the impact of therapeutic intervention. However, although the correlation between the questionnaire and symptoms seems fair, the correlation between the questionnaire and results of investigations for reflux is poor.
Investigation methods for GER all test different aspects involved in the mechanisms and characteristics of reflux. Therefore, it is not unexpected that the correlation between different techniques is extremely poor; non-acid reflux can cause esophagitis, severe heartburn can exist without esophagitis, etc. Also, the correlation between questionnaires for GER symptoms and results of pH metry and endoscopy is quite poor.
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Gastroesophageal reflux disease is the medical term for what we know as acid reflux. Acid reflux occurs when the stomach releases its liquid back into the esophagus, causing inflammation and damage to the esophageal lining. The regurgitated acid most often consists of a few compoundsbr acid, bile, and pepsin.