A reference guide to the medical and technical terms used throughout this site. Each term includes a definition and links to related content where applicable.
A condition in which the stomach produces no hydrochloric acid. The most severe form of gastric acid deficiency. Typically caused by advanced autoimmune atrophic gastritis or complete parietal cell destruction. Associated with increased risk of B12 deficiency, iron deficiency, small intestinal bacterial overgrowth, and gastric neuroendocrine tumors.
A temporary increase in gastric acid production that occurs after discontinuing proton pump inhibitor therapy. Also called rebound acid hypersecretion. The stomach compensates for prolonged suppression by overproducing acid when the medication is stopped.
The administration of sodium bicarbonate solution during a Heidelberg pH test to temporarily neutralize stomach acid and assess the stomach's ability to reacidify.
The pH-sensing component inside the Heidelberg capsule. Antimony is a semi-metal that generates a voltage proportional to the hydrogen ion concentration of the surrounding fluid, allowing continuous real-time pH measurement.
A chronic condition in which the stomach lining progressively loses its specialized acid-producing cells. Can be autoimmune or caused by chronic H. pylori infection. Leads to reduced or absent acid production and increased risk of gastric neoplasia.
The amount of gastric acid the stomach produces at rest, without stimulation. Measured as milliequivalents per hour. A low BAO indicates reduced parietal cell function.
A supplemental form of hydrochloric acid taken orally with meals by patients with suspected low stomach acid. Sometimes used as an empirical challenge to assess acid status, though unreliable compared to direct pH measurement.
The core protocol of the Heidelberg pH test. A measured dose of sodium bicarbonate solution is administered to temporarily neutralize gastric acid. The capsule measures how quickly and completely the stomach reacidifies.
The backward flow of bile from the duodenum into the stomach. Produces symptoms similar to acid reflux but does not respond to acid-suppressing medication. Can be identified by distinctive pH patterns during real-time gastric monitoring.
A wireless pH monitoring device manufactured by Medtronic. Attached to the esophageal wall to measure acid exposure in the esophagus over 48 to 96 hours. Measures esophageal pH, not gastric acid secretion.
Specialized cells in the gastric lining that produce pepsinogen, the inactive precursor to the digestive enzyme pepsin. Work in concert with parietal cells.
The lowest risk classification for medical devices regulated by the FDA. Subject to general controls but typically exempt from 510(k) requirements. The Heidelberg pH Capsule is Class I, 510(k)-exempt.
The sequence of pathological changes from chronic gastritis to atrophic gastritis to intestinal metaplasia to dysplasia to gastric adenocarcinoma. Named after Colombian pathologist Pelayo Correa.
A pattern on the Heidelberg test where the stomach responds normally to the first challenge but shows progressively weaker reacidification with each subsequent challenge. Indicates early parietal cell dysfunction.
The backward flow of duodenal contents, including bile and pancreatic secretions, into the stomach through the pyloric sphincter.
A general term for discomfort or pain in the upper abdomen, often described as indigestion. Has many possible causes including both excess and insufficient gastric acid.
Specialized cells in the gastric mucosa that release histamine in response to gastrin stimulation. Chronic elevated gastrin levels can cause ECL cell hyperplasia.
Dyspepsia without an identifiable structural or biochemical cause on standard investigation. Some patients may have undetected hypochlorhydria revealed only by direct gastric acid measurement.
Hydrochloric acid produced by parietal cells in the stomach lining. Normal gastric acid maintains a pH between 1.0 and 2.0. Functions include protein digestion, mineral absorption, bacterial killing, and intrinsic factor release.
Coordinated muscular contractions that mix stomach contents and move them toward the pyloric sphincter. Adequate gastric acid is one signal that triggers normal motility.
A hormone produced by G cells in the gastric antrum that stimulates parietal cells to produce acid. Levels rise when acid is low and fall when acid is adequate.
Delayed gastric emptying without mechanical obstruction. Low stomach acid can contribute because acid is one of the signals that triggers gastric motility.
A serological screening panel manufactured by Biohit that measures pepsinogen I, pepsinogen II, gastrin-17, and H. pylori antibodies. Does not measure actual acid output.
Specialized endocrine cells in the gastric antrum that produce gastrin. Sense stomach pH and release gastrin when pH rises above approximately 3.
Global Unique Device Identification Database. An FDA database that assigns unique identifiers to medical devices. The Heidelberg pH Capsule is listed in GUDID.
A class of medications reducing acid production by blocking histamine H2 receptors on parietal cells. Less potent than PPIs. Examples include famotidine.
A chemical messenger released by ECL cells that directly stimulates parietal cells to produce acid via H2 receptors.
A bacterium that colonizes the gastric mucosa and is the most common cause of chronic gastritis worldwide. Can lead to environmental atrophic gastritis, peptic ulcer disease, and gastric cancer.
The primary acid produced by parietal cells. Responsible for maintaining the stomach's acidic environment at pH 1.0-2.0. Essential for protein digestion, mineral absorption, bacterial defense, and intrinsic factor release.
The proton pump enzyme on parietal cells responsible for the final step of acid secretion. The target of proton pump inhibitor medications.
A condition in which the stomach produces excessive amounts of hydrochloric acid. Less common than hypochlorhydria. Associated with duodenal ulcer disease and Zollinger-Ellison syndrome.
A condition in which the stomach produces insufficient hydrochloric acid. The most common acid-related abnormality found on Heidelberg testing. Prevalence increases with age.
A pathological change in which normal gastric epithelium is replaced by cells resembling intestinal lining. Considered a premalignant condition reflecting advanced damage to the gastric mucosa.
A glycoprotein produced by parietal cells essential for vitamin B12 absorption. Loss of intrinsic factor causes pernicious anemia.
The muscular ring at the junction of the esophagus and stomach that prevents reflux. Adequate gastric acid helps signal the LES to close.
Impaired uptake of nutrients from the gastrointestinal tract. Gastric acid is required for absorption of iron, B12, calcium, magnesium, and zinc.
Impaired breakdown of food in the gastrointestinal tract. Distinguished from malabsorption. Typically originates in the stomach or pancreas.
Manufacturer and User Facility Device Experience database. An FDA database of adverse event reports. The Heidelberg pH Capsule has no adverse event reports in MAUDE.
The maximum amount of gastric acid the stomach can produce under maximal stimulation. The Heidelberg bicarbonate challenge provides a functional approximation.
The innermost lining of the stomach wall containing parietal cells, chief cells, surface mucous cells, and hormone-releasing cells. Damage leads to atrophic gastritis.
A method of measuring gastric acid by inserting a tube through the nose into the stomach. Largely abandoned due to invasiveness.
Specialized cells responsible for producing hydrochloric acid and intrinsic factor. Located primarily in the body and fundus of the stomach. Loss of parietal cells results in hypochlorhydria or achlorhydria.
A digestive enzyme that breaks down proteins. Produced as inactive pepsinogen by chief cells and activated by hydrochloric acid at pH below 3.
The inactive precursor to pepsin. Two forms exist: pepsinogen I and pepsinogen II. Serum levels are used as indirect markers of gastric mucosal status.
A type of megaloblastic anemia caused by B12 deficiency resulting from loss of intrinsic factor. Most commonly caused by autoimmune atrophic gastritis.
A measure of acidity or alkalinity on a scale from 0 to 14. Below 7 is acidic. Above 7 is alkaline. Normal gastric pH is 1.0-2.0.
A medical device legally marketed in the United States before the Medical Device Amendments of May 28, 1976. Exempt from 510(k) requirements provided intended use and design have not significantly changed. The Heidelberg pH Capsule is a preamendments device.
A class of medications that suppress gastric acid production by irreversibly blocking the hydrogen-potassium ATPase enzyme on parietal cells. Common examples include omeprazole, esomeprazole, lansoprazole, and pantoprazole.
The muscular valve at the junction of the stomach and duodenum. When incompetent, bile can flow backward into the stomach causing bile reflux.
The process by which the stomach returns to baseline acidic pH after neutralization. The speed, completeness, and consistency of reacidification reveals parietal cell functional status.
The graphical representation of pH changes over time during a Heidelberg test. Different curve patterns correspond to normal function, hypochlorhydria, achlorhydria, hyperchlorhydria, bile reflux, and diminishing secretory reserve.
The temporary overproduction of gastric acid after discontinuing PPI therapy. Can last several weeks and creates symptoms that mimic the original condition.
The stomach's ability to sustain acid production under repeated or prolonged demand. A stomach with adequate reserve maintains consistent reacidification across all challenges.
A condition in which bacteria colonize the small intestine in abnormally large numbers. Gastric acid is the primary barrier preventing bacterial transit from stomach to small intestine.
A wireless motility capsule formerly manufactured by Medtronic. Measured pH, pressure, and transit time. Discontinued and no longer commercially available.
The alkaline solution administered during the Heidelberg challenge protocol. Temporarily neutralizes gastric acid, raising the pH. The stomach's response reveals its acid production capacity.
The tenth cranial nerve providing parasympathetic innervation to the stomach. Vagal dysfunction can impair acid production even when parietal cells are intact.
A rare condition caused by gastrin-secreting tumors driving excessive acid production. Results in severe hyperchlorhydria, peptic ulcers, and diarrhea.
A regulatory status for certain Class I and Class II devices exempt from premarket notification. The Heidelberg pH Capsule is 510(k)-exempt under 21 CFR §876.1400.
The regulation stating that establishment registration does not denote FDA approval, and any representation creating that impression constitutes misbranding.
The Heidelberg pH Capsule is a Class I medical device, 510(k)-exempt, listed with the U.S. Food and Drug Administration under 21 CFR §876.1400. Listing of a device does not denote FDA approval, clearance, or endorsement.