Achlorhydria

Achlorhydria indicates the complete lack of production of gastric acid by the gastric parietal cells. Hypochlorhydria is a reduction in the production of gastric acid.

Both achlorhydria and hypochlorhydria are commonly the consequence of chronic atrophic gastritis, which is usually caused by autoimmune or Helicobacter pylori related destruction of acid producing gastric parietal cells.

Patients are usually asymptomatic but may present with signs and/or symptoms of iron, cobalamin (vitamin B12), or calcium deficiency. Patients with hypochlorhydria and achlorhydria are predisposed to enteric infection with organisms such as Clostridium difficile, Salmonella, and Campylobacter.

There is no specific treatment. It is reasonable to test for H pylori and, if present, eradicate it. Other treatments aim to prevent or treat complications arising from achlorhydria.

Although the prognosis is excellent, it carries a small increased risk for the development of gastric adenocarcinoma and gastric neuroendocrine tumors from enterochromaffin cell hyperplasia.

Achlorhydria indicates the complete lack of production of gastric acid (i.e., hydrochloric acid), even after stimulation with secretagogues (e.g., pentagastrin [gastrin analog], histamine, betazole [histamine analog], or a meal). Serum gastrin is a marker for gastric acid output. A decrease in gastric acid interrupts a negative feedback pathway controlling gastrin secretion and leads to elevated serum gastrin levels (hypergastrinemia).[1]Schubert ML, Peura DA. Control of gastric acid secretion in health and disease. Gastroenterology. 2008 Jun;134(7):1842-60. http://www.ncbi.nlm.nih.gov/pubmed/18474247?tool=bestpractice.com [2]Brand SJ, Stone D. Reciprocal regulation of antral gastrin and somatostatin gene expression by omeprazole-induced achlorhydria. J Clin Invest. 1988 Sep;82(3):1059-66. http://www.jci.org/articles/view/113662/pdf http://www.ncbi.nlm.nih.gov/pubmed/2901431?tool=bestpractice.com [3]Wu SV, Giraud A, Mogard M, et al. Effects of inhibition of gastric secretion on antral gastrin and somatostatin gene expression in rats. Am J Physiol. 1990 May;258(5 Pt 1):G788-93. http://www.ncbi.nlm.nih.gov/pubmed/1692193?tool=bestpractice.com [4]Manela FD, Ren J, Gao J, et al. Calcitonin gene-related peptide modulates acid-mediated regulation of somatostatin and gastrin release from rat antrum. Gastroenterology. 1995 Sep;109(3):701-6. http://www.ncbi.nlm.nih.gov/pubmed/7657098?tool=bestpractice.com ​ Hypochlorhydria is a reduction in the production of gastric acid.

The most common cause of achlorhydria is chronic atrophic gastritis of the fundus and corpus (body) of the stomach (also termed gastric corpus atrophy, oxyntic gastric atrophy, chronic atrophic gastritis, and gastric atrophy). This is characterized histopathologically by the loss of oxyntic glands that contain acid-producing parietal cells in the fundus and body of the stomach.[5]El-Zimaity H. Gastritis and gastric atrophy. Curr Opin Gastroenterol. 2008 Nov;24(6):682-6. http://www.ncbi.nlm.nih.gov/pubmed/19122515?tool=bestpractice.com [6]Sepulveda AR, Patil M. Practical approach to the pathologic diagnosis of gastritis. Arch Pathol Lab Med. 2008 Oct;132(10):1586-93. http://www.ncbi.nlm.nih.gov/pubmed/18834216?tool=bestpractice.com [7]Rugge M, Genta RM. Staging and grading of chronic gastritis. Hum Pathol. 2005 Mar;36(3):228-33. http://www.ncbi.nlm.nih.gov/pubmed/15791566?tool=bestpractice.com ​ Chronic atrophic gastritis typically occurs from chronic inflammation, predominantly from chronic Helicobacter pylori infection or from autoimmune gastritis.[8]Shah SC, Piazuelo MB, Kuipers EJ, et al. AGA clinical practice update on the diagnosis and management of atrophic gastritis: expert review. Gastroenterology. 2021 Oct;161(4):1325-32.e7. https://pmc.ncbi.nlm.nih.gov/articles/PMC8740554 http://www.ncbi.nlm.nih.gov/pubmed/34454714?tool=bestpractice.com