A Prospective Cohort Study on Endoscopic Features of Upper Gastrointestinal Tract at High Altitude (Zaduo County)

The severity of reflux esophagitis (RE) was evaluated according to the Los Angeles (LA) classification[1]. Mucosal breaks were defined as visible discontinuities of the esophageal squamous epithelium. The grading criteria were as follows:

LA Grade A: One or more mucosal breaks, each no longer than 5 mm, confined to the mucosal folds.

LA Grade B: One or more mucosal breaks longer than 5 mm, but not continuous between the tops of two mucosal folds.

LA Grade C: Mucosal breaks continuous between the tops of two or more mucosal folds, involving less than 75% of the esophageal circumference.

LA Grade D: Mucosal breaks involving at least 75% of the esophageal circumference. The proportion of reflux esophagitis was defined as the number of patients diagnosed with reflux esophagitis divided by the total number of enrolled participants.

The extent of gastric atrophy was determined by tracing the endoscopic atrophic border (the "cut-off line"). Based on the location of the endoscopic atrophic border, Kimura and Takemoto proposed an endoscopic classification of gastric atrophy comprising two main types: closed type (C type) and open type (O type). These two main types are further subdivided into three closed types (C-1, C-2, and C-3) and three open types (O-1, O-2, and O-3). Closed type C-1 is characterized by endoscopic atrophic changes confined to the antrum. In types C-2 and C-3, the atrophic changes extend parabolically above the angulus. The differentiation between C-2 and C-3 is based on the location of the atrophic border in relation to the middle of the lesser curvature of the stomach: in C-2, the atrophic border lies below this level, whereas in C-3, it lies above it. In the open types, the atrophic border lies between the lesser curvature and the anterior wall in O-1, on the anterior wall in O-2, and between

Assessment of the Gastroesophageal Flap Valve (GEFV)

The appearance and compliance of the GEFV during quiet respiration were graded according to the Hill classification:

Grade I: The GEFV appears as a well-defined, symmetrical fold compressing the tip of the endoscope.

Grade II: The GEFV appears as a poorly defined, wavy fold that opens with respiration, allowing partial visualization of the cardia.

Grade III: The GEFV is absent; the cardia is clearly visible and opens widely with respiration, exposing the gastric fundus.

Grade IV: The cardia is permanently open, exhibiting a hiatal hernia appearance with retrograde prolapse of the gastric mucosa into the esophagus.

Based on the urea breath test results, endoscopic findings, and the history of H. pylori eradication therapy, infec-tion status was divided into three groups: negative, positive, and eradication. Positive status was defined as a positive urea breath test or endoscopic features suggestive of current Helicobacter pylori infection. Eradication status was defined as negative urea breath test together with either a documented his-tory of eradication therapy or definite endoscopic atrophy (Kimura-Takemoto grade ≥ C-II, that is, the atrophic border extending beyond the gastric angle). The remaining cases were considered to be H. pylori-negative.