Figure 9.8 Percentage of patients with complete bolus transit in 350 patients with various manometric diagnoses. While all patients with achalasia and scleroderma have incomplete bolus transit, more than half of patients with distal esophageal spasm (DES) and ineffective esophageal motility (IEM) have complete bolus transit (51% and 55%, respectively). Almost all patients with nutcracker esophagus, normal esophageal manometry, and isolated lower esophageal sphincter (LES) abnormalities have complete bolus transit for liquid.
Source: Modified from Tutuian and Castell [6].
In summary, the addition of MII to manometry (MII‐EM) incorporates two complementary techniques that, together, provide a more detailed evaluation of both aspects of esophageal function: esophageal contractile activity and bolus transit. The clinical applications of this approach are discussed in Chapter 5.
Combined multichannel intraluminal impedance and pH for detection of acid and nonacid gastroesophageal reflux
The pathophysiologic role of acid in GERD has been well established in studies in both animals and humans [7]. Until recently, measuring GER was based solely upon esophageal pH monitoring, which bases detection of reflux of acidic material into the esophagus on changes in hydrogen ion concentration (i.e. drops in esophageal pH to below 4.0) [8]. In a number of patients, reflux symptoms persist despite treatment with medications that decrease gastric acid secretion; recent studies have shown that these symptoms can be caused by reflux having pH greater than 4 (i.e. nonacid reflux or weakly acidic reflux) [9]. In fact, when the contents of the stomach are buffered (in the post‐prandial period or during treatment with potent acid‐suppressing medications like proton‐pump inhibitors), a significant proportion of GER is nonacid and therefore not accurately detectable by conventional pH recording [10–13]. This is highlighted by the fact that the likelihood of a positive pH test in acid‐suppressed patients is indeed very low [14]. This limitation of pH‐metry has created the need for a method that can accurately measure nonacid reflux.
Figure 9.9 Example of rumination on HRIM. Length of the esophagus is shown along the y‐axis, with the distal end of the y‐axis representing catheter position within the stomach. Pressures > 30 mmHg are circled in black. Low impedance, indicative of fluid, is shown in purple. Time is shown along the x‐axis. A rise in intragastric pressure is highlighted by an arrow, which is subsequently followed by movement of liquid from the stomach to the esophagus, as represented by the movement of purple and highlighted by the arrow.
Source: Courtesy of Dr. David Katzka.
Several techniques have been considered in the past for the study of nonacid or alkaline reflux, including aspiration, scintigraphy, ambulatory pH monitoring, and bilirubin monitoring (Bilitec) [15–19], all of which have certain limitations. Aspiration studies allow for only short analysis periods, and the accuracy of enzymatic determination of the contents of the aspirates has been questioned [18, 20]. Scintigraphic studies are expensive, involve radiation exposure, and are usually limited to short monitoring periods [16]. During ambulatory pH monitoring, a pH of 7 or greater has been used as the definition of “alkaline” reflux, but increased saliva production or bicarbonate secreted by esophageal submucosal glands confounds measurements by increasing esophageal pH in the absence of reflux [21]. Some authors propose that reflux can be detected by pH‐metry even when intraesophageal pH remains greater than 4.0 through measurement of pH decreases of greater than 1 unit [22]. However, ingestion of acidic foods can mimic reflux by provoking pH drops of greater than 1 unit [23]; furthermore, pH‐metry is unable to detect nonacid reflux that occurs in the absence of pH changes or with small pH changes (<1 unit) [9]. Monitoring with the Bilitec probe is based on the presence of bilirubin and is therefore incapable of measuring bile‐free nonacid reflux. Additionally, bilirubin monitoring requires a special diet to avoid false‐positive readings [18].