Gastric acid analysis is rarely done in current practice. When conducted, samples of stomach contents obtained via nasogastric tube are used to measure gastric acid output in a basal and stimulated state. This information may be useful in a patient who develops a recurrent ulcer Surgery 
after surgical vagotomy for peptic ulcer disease. In this case, a positive acid response to stimulation (sham feeding) indicates an incomplete vagotomy.
The test also is used to evaluate a patient with elevated serum gastrin levels. Hyperchlorhydria in the presence of elevated gastrin usually indicates Zollinger-Ellison syndrome Gastrinoma A gastrinoma is a gastrin-producing tumor usually located in the pancreas or the duodenal wall. Gastric acid hypersecretion and aggressive, refractory peptic ulceration result (Zollinger-Ellison... read more 
. Hypochlorhydria in the presence of elevated gastrin indicates impairment of acid output, such as occurs in pernicious anemia, atrophic gastritis Autoimmune Metaplastic Atrophic Gastritis Autoimmune metaplastic atrophic gastritis is an inherited autoimmune disease that attacks parietal cells, resulting in hypochlorhydria and decreased production of intrinsic factor. Consequences... read more 
, and Ménétrier disease Ménétrier Disease Gastritis is inflammation of the gastric mucosa caused by any of several conditions, including Helicobacter pylori infection, drugs (nonsteroidal anti-inflammatory drugs [NSAIDs], alcohol),... read more and after inhibition of gastric acid secretion by potent antisecretory medications.
To do gastric analysis, a nasogastric tube is inserted and the gastric contents are aspirated and discarded. Gastric juice is then collected for 1 hour, divided into four 15-minute samples. These samples represent basal acid output.
Gastric analysis can also be done during catheter-based esophageal pH-monitoring Catheter-Based pH Monitoring Ambulatory 24-hour esophageal pH monitoring with or without intraluminal impedance testing is currently the most common test for quantifying gastroesophageal reflux (see the American College... read more .
Complications of gastric analysis are very rare.
