Esophageal Function Testing

First submitted by:
Shawn Tsuda
(see History tab for revisions)

Esophageal function testing (esophageal manometry and 24 hour pH monitoring) has been based on the same technology for decades. Recently, however, several technical improvements have transformed the field of esophageal diagnostic testing. Prolonged (up to 48 hours) monitoring of the esophageal pH is now possible with the wireless pH capsule monitoring and more detailed pressure topography of the esophagus has been achieved by the recent development of the highresolution manometry.

Esophageal manometry and ambulatory pH monitoring were developed in the 70s. With time, the relevance of these techniques in clinical practice became evident. Johnston et al. in 1993 showed how esophageal manometry changed the management of 20% of patients with non-cardiac chest pain and GERD and of 60% of those with dysphagia. Eckardt reported in 1999 that the introduction of pH monitoring in their clinical practice changed management in 42-66%of the patients. Since that time, many studies have enhanced our understanding of the utility of this diagnostic modality in the management of patients with GERD and primary esophageal motility disorders. For instance, investigators at UCSF studied with esophageal function tests 822 consecutive patients who had a clinical diagnosis of GERD based on symptoms and endoscopic finding. They showed that only 70% of them had abnormal reflux on pH monitoring. Symptoms such as heartburn and regurgitation were also no more frequent in patients who had genuine reflux than in those who did not. Thus, symptomatic evaluation could not distinguish between the two groups. In addition, endoscopy could not confirm a diagnosis of GERD based on symptoms, because the esophageal mucosa was normal in about half of patients with GERD. In addition, there is a significant interobserver variation between endoscopists, particularly for low-grade esophagitis. The findings of the esophageal function tests are therefore important to achieve an objective diagnosis and to avoid the prescription of inappropriate acid suppression medications or the performance of an antireflux operation.

Ambulatory pH monitoring also establishes a temporal correlation between symptoms and episodes of reflux. Such a correlation is particularly important when atypical symptoms of gastroesophageal reflux disease, such as cough, are present, as it identifies patients most likely to benefit from anti-reflux surgery. For instance, Patti et al. have showed that following laparoscopic fundoplication, typical symptoms resolved in 90% of patients, and respiratory symptoms resolved in 83% of patients when a strong temporal correlation between cough and reflux was found on pH monitoring. Moreover, ambulatory pH monitoring allows stratifying patients with GERD on the basis of its severity. Specifically, pH monitoring identifies a subgroup of patients characterized by a worse reflux profile because of more acid reflux in the distal and proximal esophagus, and slower acid clearance. These patients more frequently develop Barrett’s metaplasia and thus might benefit from early antireflux surgery. Lastly, ambulatory pH monitoring provides baseline data that may prove useful postoperatively if symptoms persist or recur postoperatively. For instance, when a patient has heartburn postoperatively it is assumed that the fundoplication has failed and acid reducing medications are prescribed. However, when ambulatory pH monitoring is performed, it shows that about two-thirds of patients who are taking acid-reducing medications postoperatively have a normal reflux status.

This technology has also improved our ability of predicting the outcome of laparoscopic antireflux surgery. In a multivariate analysis, Campos et al. showed that an abnormal ambulatory pH monitoring (together with a good response to acid suppression therapy and the presence of typical symptoms such as heartburn), was important in predicting a successful outcome of laparoscopic antireflux surgery (16). The findings of this work influenced the practice of gastroenterologist and surgeons, for almost 10 years. This work, however, left some questions unanswered. It was not clear how to treat patients who still experienced typical or atypical symptoms while receiving medical therapy. Specifically it was not clear if another disease was responsible or if a non-acid form of reflux was causing the symptoms. The breakthrough came with the development of esophageal impedance, which detects the flow of liquids and gas through hollow viscera, such as the esophagus. When used in combination with esophageal pH monitoring, this technique is able to detect both the transit of the refluxate and its pH throughout the esophagus. In 2004, Tamhankar et al. showed that in normal subjects, medical therapy did not affect the number of reflux episodes or their duration, but it just changed the pH of the refluxate, being weakly acidic or non acidic. This and other studies partially explained why patients could experience symptoms while treated with acid suppressing medications. Mainie and Castell have shown that patients with persistent symptoms on acid suppressive therapy can be successfully treated surgically when multichannel intraluminal impedance and pH monitoring shows a positive association between symptoms and reflux, regardless of its pH. This observation was true for both typical and atypical symptoms of reflux.. For instance, Mainie and Castell have shown that in patients with persistent cough despite twice-daily proton pump inhibitor laparoscopic antireflux surgery is effective in improving atypical symptoms when a correlation between reflux and symptoms equal or superior to 50%, is present. The implications of these investigations are important, because they seem to finally validate the theory that it is the presence of reflux, regardless of it pH that causes GERD. Two corollaries follow: a) impedance pH monitoring should be performed in patients with persistent symptoms while on medical therapy and b) the surgical reestablishment of the esophageal competence as a barrier to the reflux can determine good outcomes. The rapid evolution of the technology behind the esophageal function testing has also introduced over the last years in the clinical practice two other diagnostic tools: the wireless pH capsule monitoring and the high-resolution manometry. They had less impact that multichannel intraluminal impedance and pH monitoring in further improving our understanding of foregut diseases, but advances in technology and future research studies will clarify their role in clinical practice. The wireless pH capsule monitoring was developed to avoid the fastidious pH monitoring wire that remained in the esophagus across the nostril for 24 hours. This technique, which involves the endoscopic placement of the capsule to the esophageal mucosa, has important advantages: it has no connecting wire to the recorder and it is able to record up to 48 hours of data. However, the system has several limitations: it records only the pH in the distal esophagus, it can cause chest pain or discomfort that in some case has warranted early endoscopic removal, and it can detach early (<24 hours) from the esophagus (22). When this happens and by falling into the stomach, the capsule will record an acidic pH, thus creating a false positive study. In addition, the wireless capsule is placed transorally by endoscopy. This has the potential to create false positive or false negatives, depending on whether the capsule is placed to close or too far from the gastroesophageal junction. High-resolution manometry provides detailed pressure topography of the esophagus. This allows a better identification than conventional manometry of segments of compartmentalized esophageal pressurization and better discrimination of conditions such as distal esophageal spasm, nutcracker esophagus, and vigorous achalasia.

References

2. Johnston PW, Johnston BT, Collins BJ, Collins JS, Love AH. Audit of the role of oesophageal manometry in clinical practice. Gut. 1993;34(9):1158-61
8. Patti MG, Arcerito M, Feo CV, Worth S, De Pinto M, Gibbs VC, Gantert W, Tyrrell D, Ferrell LF, Way LW. Barrett’s esophagus: a surgical disease. J Gastrointest Surg. 1999;3(4):397-403
10. Khajanchee YS, O’Rourke RW, Lockhart B, Patterson EJ, Hansen PD, Swanstrom LL. Postoperative symptoms and failure after antireflux surgery. Arch Surg. 2002;137(9):1008-13
11. Lord RV, Kaminski A, Oberg S, Bowrey DJ, Hagen JA, DeMeester SR, Sillin LF, Peters JH, Crookes PF, DeMeester TR. Absence of gastroesophageal reflux disease in a majority of patients taking acid suppression medications after Nissen fundoplication. J Gastrointest Surg. 2002;6(1):3-9
12. Campos GM, Peters JH, DeMeester TR, Oberg S, Crookes PF, Tan S, DeMeester SR, Hagen JA, Bremner CG. Multivariate analysis of factors predicting outcome after laparoscopic Nissen fundoplication. J Gastrointest Surg. 1999;3(3):292-300