Achlorhydria, in simple terms, means the absence of hydrochloric acid in gastric secretions and has been defined by multiple separate systems in reference to gastric acid secretion.
First, achlorhydria has been defined by a peak acid output in response to a maximally effective stimulus that results in an intragastric pH greater than 5.09 in men and greater than 6.81 in women. Second, achlorhydria has been defined by a maximal acid output of less than 6.9 m/mole/h in men and less than 5.0 m/mole/h in women. Third, achlorhydria has been defined as a ratio of serum pepsinogen I/pepsinogen II of less than 2.9.
Several medical conditions and specific gastric surgery can lead to achlorhydria; all of which are described in this article. Achlorhydria is associated with intestinal metaplasia of the gastric mucosa, which may lead to dysplasia, and is hence considered a premalignant condition.