White opaque substance visualized by magnifying narrow-band imaging is associated with intragastric acid conditions

Abstract

Background and study aims: The presence of white opaque substance (WOS) is an endoscopic marker of intestinal metaplasia. Considering that the nature of WOS is absorbed lipid droplets, lipase plays an important role in the lipid absorption process and is inactivated at strong acidity. WOS may only be present in a hypochlorhydria state following Helicobacter pylori infection, and, thus, may not be highly sensitive marker, especially in H. pylori- eradicated patients. We investigated the relationship between WOS and gastric acid conditions.

Patients and methods: A total of 501 patients were retrospectively evaluated for the presence of WOS at 2 regions of interest using magnifying narrow-band imaging. The pH level of collected gastric juice was also measured. Study end points were (1) prevalence of WOS and its relationship with gastric juice pH in 3 groups: H. pylori- uninfected , H. pylori- infected, and H. pylori -eradicated; (2) the relationship between prevalence of WOS and gastric juice pH before and after proton pump inhibitor (PPI) administration in 29 H. pylori -eradicated cases.

Results: Prevalence of WOS was 0 % (0 /206), 28.4 % (31/109), and 3.2 % (6/186) in the H. pylori -uninfected, H. pylori -infected, and H. pylori -eradicated groups, respectively. Mean gastric juice pH was significantly higher in WOS-positive cases than in WOS-negative cases in the H. pylori -infected and H. pylori -eradicated groups ( P < 0.0001). Mean gastric juice pH increased from 1.1 to 6.9 after PPI administration and WOS prevalence increased from 0 % (0/29) to 45 % (13/29) of cases.

Conclusion: The prevalence of WOS is closely associated with the neutralization of intragastric pH.

Fig. 1

Definition of WOS-positive or WOS-negative. a WOS was defined as positive when a white substance was observed by M-NBI that obscured the subepithelial capillaries of the intervening part between crypt openings in the region of interest, regardless of LBC coexistence. b Normal mucosa. c LBC positive but WOS-negative mucosa was defined as WOS-negative.

Fig. 2

Prevalence of WOS in H. pylori -uninfected, H. pylori -infected, and H. pylori -eradicated groups.

Fig. 3

Relationship between the presence of WOS and fasting gastric juice pH level in H. pylori -uninfected, H. pylori -infected, and H. pylori -eradicated groups.

Fig. 4

Relationship between the presence of WOS and fasting gastric juice pH before and after PPI administration in 29 H. pylori -eradicated cases with gastric epithelial neoplasia.

Fig. 5

A representative H. pylori -eradicated case with WOS appearance: endoscopic findings before and after PPI administration. WOS is not observed before PPI administration ( a  –  d ). However, WOS appears dramatically after 14 d PPI administration ( a’  –  d’ ). Fasting gastric juice pH changed from pH1 to pH7 following PPI administration.