Are H. Pylori infections the most common cause of both gastric and duodenal ulcers? Is the urea breath test a useful diagnostic for both kinds?

Question

H. pylori infections are a frequent cause of peptic ulcers, and a positive result from a urea breath test indicating the likely presence of H. pilori may be followed by treatment that includes one or more antibiotic.

The urea breath test is a rapid diagnostic procedure used to identify infections by Helicobacter pylori, a spiral bacterium implicated in gastritis, gastric ulcer, and peptic ulcer disease. It is based upon the ability of H. pylori to convert urea to ammonia and carbon dioxide. Urea breath tests are recommended in leading society guidelines as a preferred non-invasive choice for detecting H. pylori before and after treatment

The test introduces labeled urea (¹³C or ¹⁴C) which the bacteria regularly breaks down to produce ammonia to neutralize acidity. A bi-product is carbon dioxide, some of which is absorbed into the blood. When labeled urea is introduced and acted upon by H. Pylori a patient may exhale ab enhanced amount of labeled carbon some time later (e.g. a half hour).

Question: Are H. Pylori infections the most common cause of both gastric and duodenal ulcers? Is the urea breath test a useful diagnostic for both kinds?

Answer 1

This is an excellent description of exactly how the urea breath test is done and why it is useful in detecting whether there might be H. pylori.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1123218/

Berger A. Helicobacter pylori breath tests. BMJ. 2002;324:1263. doi: 10.1136/bmj.324.7348.1263 PMCID: PMC1123218 PMID: 12028983

As described in this paper,

“Patients first drink a sachet of orange juice or citric acid. This rapidly closes the duodenal sphincter to contain the stomach contents. They are then asked to blow through a straw into a glass tube with a screw cap lid. This provides the baseline sample. Next, they consume a drink containing 13C enriched urea (about 100 ml) and after 30 minutes repeat the blowing exercise into a second tube. This provides the post-dose sample. Both samples are sent away for carbon dioxide isotope analysis by mass spectrometry (laboratories usually return the results within a few days). The level of 13C in the baseline sample will be normal. If levels rise in the post-dose sample, this suggests the presence of H pylori. The enriched urea provided by the testing kit must have been broken down to produce high levels of 13C in the breath and this implies the presence of urease excreting H pylori in the stomach. “

Peptic ulcer disease is a term that includes both ulcers in the stomach (i.e., gastric ulcers) and ulcers in the duodenum (duodenal ulcers). H. pylori is involved in the pathogenesis of both gastric ulcers and duodenal ulcers but the mechanisms are different.

This lecture prepared by Dr. Mahra Arafah and Dr. Ahmed Al Humaidi for medical education at the King Saud University and posted on slide share provides an especially understandable explanation of the complex pathogenesis of peptic ulcers. To understand better the role of H. pylori in the pathogenesis of gastric ulcers compared with duodenal ulcers, see in particular slides 21-26. https://slideplayer.com/slide/13083448/

What is explained in detail in the lecture is summarized in the abstract of a paper by Walker and Crabtree (1998):

“Helicobacter pylori is a gram-negative spiral bacterium confined to the habitat of gastric-type epithelium. [bolded for emphasis] H. pylori causes duodenal ulceration by a cumulative effect of antral predominant gastritis with increased acid secretion, consequent gastric metaplasia in the duodenum (a site of further colonization by H. pylori), duodenitis, reduced duodenal bicarbonate secretion, and mucosal damage.”

https://pubmed.ncbi.nlm.nih.gov/9928373/

As explained in a 1996 article by Khulusi et al.:

“Gastric metaplasia (GM) of the duodenum is the replacement of groups of duodenal epithelial cells by those with a gastric mucosal phenotype. It is a feature of the duodenal bulb and is generally believed to occur as a nonspecific response to acid/peptic damage and is strongly associated with duodenal ulceration.”

Khulusi S, Badve S, Patel P, et al. Pathogenesis of gastric metaplasia of the human duodenum: role of Helicobacter pylori, gastric acid, and ulceration. Gastroenterology. 1996 Feb;110(2):452-8. doi: 10.1053/gast.1996.v110.pm8566592. PMID: 8566592.

In answer to your question, the urea breath test is used to detect/diagnosis H. pylori in the stomach. The test can be useful in evaluating people with symptoms of duodenal ulcer but does not specifically detect/diagnose H. pylori colonization of the duodenum.