achlorhydria

Achlorhydria is the absence of hydrochloric acid in the stomach. It can be total or near-total and is distinct from hypochlorhydria, where acid is merely reduced. The condition may be congenital or acquired and may be temporary or permanent.

Acquired achlorhydria most often results from autoimmune atrophic gastritis with parietal-cell loss and pernicious anemia. It can also follow extensive gastric surgery, chronic Helicobacter pylori infection, or long-term use of acid-suppressing medications. Congenital achlorhydria is rare.

Loss of gastric acidity impairs iron and vitamin B12 absorption, fosters bacterial overgrowth, and can cause nutritional deficiencies. Autoimmune achlorhydria is associated with an increased long-term risk of gastric neoplasia, including adenocarcinoma and neuroendocrine tumors.

Diagnosis relies on elevated fasting gastrin and gastric pH testing showing absent acidity, with endoscopic biopsies revealing mucosal atrophy and loss of parietal cells, sometimes with intestinal metaplasia.

Management targets deficiencies and the underlying cause. Vitamin B12 replacement is essential for pernicious anemia, and iron supplementation may be needed. If present, Helicobacter pylori eradication may be attempted, and surveillance for gastric neoplasia is advised.

Prognosis depends on etiology and mucosal changes; with treatment, deficiencies improve, but cancer and neuroendocrine tumor risks persist in autoimmune atrophic gastritis.