Achlorhydria

Achlorhydria indicates the inability to produce gastric acid. This is most commonly caused by gastric atrophy. Gastric atrophy, with or without autoimmune gastritis, is present in about 15% of older people and is thought to be initiated by infection with Helicobacter pylori.

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

Achlorhydria may interfere with the absorption of certain drugs including thyroxine, ketoconazole, itraconazole, and dipyridamole.

The physiologic response to achlorhydria/gastric atrophy is hypergastrinemia. This is the most common cause of hypergastrinemia.

Although the prognosis is excellent, it carries a small increased risk for the development of gastric adenocarcinoma and gastric carcinoid tumor.

Achlorhydria indicates the inability to produce 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

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), which is characterized histopathologically as loss of oxyntic glands.[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 It is the oxyntic (oxys: Greek for acid) glands that contain the acid-producing parietal cells.