A helix-shaped bacterium which hovers in the stomach can cause long-term problems and increase the risk of cancer.
By Dr Lee Yuk Tong, Specialist in Gastroenterology & Hepatology, Hong Kong Adventist Hospital
More than one in every two people becomes infected with the Helicobacter pylori bacteria at some point in their lives. Often this helix-shaped bacterium causes few noticeable symptoms, meaning it can hover unnoticed in the stomach. But left to linger too long, it can cause ulcers and eventually stomach cancer.
Most infections of Helicobacter pylori – often referred to as H. pylori - occur before the age of 10 through person-to-person transmission, and family clustering of the infection is common. However, it is unlikely for adults to acquire the infection through eating raw food, daily social contact or sharing chopsticks.
Once in the stomach, the bacteria can thrive and without antibiotic therapy may become a life-long infection, causing damage to the stomach.
The most common damage observed is superficial gastritis of the stomach – or inflammation of the stomach lining – which if persists can become chronic active gastritis. This in turn can affect the stomach lining irreversibly, bringing changes which may develop into precancerous lesions, and in a few patients, gastric cancer, or gastric MALT lymphoma (mucosa-associated lymphoid tissue lymphoma).
Most patients with gastritis do not have any symptom but 10-15 per cent will develop peptic ulcer disease and possibly experience abdominal pain or pass dark blood-tainted stools because of gastrointestinal bleeding.
If the condition develops into gastric cancer, the patient may suffer vomiting, anaemia, loss of appetite and weight loss.
Since H. pylori infection is closely related to peptic ulcers and gastric cancer, patients with a history of peptic ulcer disease, those who have undergone endoscopic resection of early gastric cancer, or have a family history of gastric cancer, should be tested for the bacteria and undergo medication to eradicate it if it is found.
As infection with H. pylori can increase the risk of ulcers associated with aspirin and non-steroid anti-inflammatory drugs (commonly used analgesics), it is also advisable to check for the presence of H. pylori infection if you are taking these medications in the long term.
Early detection and eradication of the bacteria may help prevent the development of gastric cancer. However, if the infection is only eradicated in late adulthood, irreversible damage (intestinal metaplasia or dysplasia) may have already occurred due to chronic infection and the cancer prevention effect is lower.
There are several methods used to detect the infection which include blood serology tests, urea breath test and stool antigen test. Of these, the latter two are more accurate and can be used before and after antibiotic treatment.
The infection can also be diagnosed during endoscopic examination with a biopsy from the stomach, with a commercial kit called rapid urease test, and a culture test which tests antibiotic sensitivity.
With the exception of the serology test, the accuracy of all these tests is affected by the use of acid suppressive drug and antibiotic use. Therefore, patients should stop taking drugs at least two weeks before undergoing the tests.
The advantage of the endoscopy examination is that it also allows the doctor to look for any related stomach damage and even early gastric cancer.
If H. pylori is detected, the treatment involves a combination of high dose proton pump inhibitor (an acid suppressive drug) together with two antibiotics lasting seven to 14 days.
This treatment carries a success rate of more than 85 per cent; however, doctors usually recommend a repeat test around six to eight weeks later in the case of high risk patients.
In some cases, it may be necessary to repeat the treatment. However, once successfully eradicated, reinfection of this unwelcome bacterium is uncommon.