DiagnosticEvaluation

Including such methods as

Barium studies of the proximal gastrointestinal tract,

Endoscopy

Several biopsy urease tests

Serologic testing,

The ¹³C- or ¹⁴C-urea breath test (UBT),

and the fecal H. pylori antigen test

In view of the poor predictive value of abdominal pain for the presence of a gastroduodenal ulcer and the multiple disease processes that can mimic this disease, the clinician is often confronted with having to establish the presence of an ulcer. Documentation of an ulcer requires either a radiographic (barium study) or an endoscopic procedure. However, a large percentage of patients with symptoms suggestive of an ulcer have NUD; empirical therapy is appropriate for individuals who are otherwise healthy and <45, before embarking on a diagnostic evaluation.

Barium studies of the proximal gastrointestinal tract are still commonly used as a first test for documenting an ulcer. The sensitivity of older single-contrast barium meals for detecting a DU is as high as 80%, with a double-contrast study providing detection rates as high as 90%. Sensitivity for detection is decreased in small ulcers (<0.5 cm), presence of previous scarring, or in postoperative patients. A DU appears as a well-demarcated crater, most often seen in the bulb. A GU may represent benign or malignant disease. Typically, a benign GU also appears as a discrete crater with radiating mucosal folds originating from the ulcer margin. Ulcers >3 cm in size or those associated with a mass are more often malignant. Unfortunately, up to 8% of GUs that appear to be benign by radiographic appearance are malignant by endoscopy or surgery. Radiographic studies that show a GU must be followed by endoscopy and biopsy.

Endoscopyprovides the most sensitive and specific approach for examining the upper gastrointestinal tract. In addition to permitting direct visualization of the mucosa, endoscopy facilitates photographic documentation of a mucosal defect and tissue biopsy to rule out malignancy (GU) or H. pylori.

Tests for H. pylori can be divided into two groups: invasive tests, which require upper gastrointestinal endoscopy and are based on the analysis of gastric biopsy specimens, and noninvasive tests.

Although the methods for diagnosing H. pylori a brief summary will be included here (Table). Several biopsy urease tests have been developed (PyloriTek, Clotest, Hpfast, Pronto Dry) and have a sensitivity and specificity of >90 to 95%. Several noninvasive methods for detecting this organism have been developed. Three types of studies routinely used include serologic testing, the ¹³C- or ¹⁴C-urea breath test (UBT), and the fecal H. pylori antigen test.

Endoscopy often is not performed in the initial management of young dyspeptic patients without worrying symptoms but is commonly used in older people to exclude malignancy. If endoscopy is performed, the most convenient biopsy-based test is the biopsy urease test, in which one large or two small antral biopsy specimens are placed into a gel containing urea and an indicator. The presence of H. pylori urease elicits a color change, which often occurs within minutes but can require up to 24 h. Histologic examination of biopsy specimens is accurate, provided that a special stain (e.g., a modified Giemsa or silver stain) permitting optimal visualization of H. pylori is used. If biopsies from both antrum and corpus are obtained, histologic study yields additional information, including the degree and pattern of inflammation, atrophy, metaplasia, and dysplasia. Microbiologic culture is most specific but may be insensitive because of difficulty with H. pylori isolation. Once cultured, the identity of H. pylori can be confirmed by its typical appearance on Gram's stain and its positive reactions in oxidase, catalase, and urease tests. Moreover, the organism's antibiotic sensitivities can be determined. The occasional biopsy specimens containing the less common non-pylorihelicobacters give only weakly positive results in the biopsy urease test. Positive identification of these bacteria requires visualization of the characteristic long, tight spiral bacteria in histologic sections.

Noninvasive H. pylori testing is now the norm if gastric cancer does not need to be excluded. The most consistently accurate test is the urea breath test. In this simple test, the patient drinks a labeled urea solution and then blows into a tube. The urea is labeled with either the nonradioactive isotope ¹³C or a minute dose of the radioactive isotope ¹⁴C. If H. pylori urease is present, the urea is hydrolyzed and labeled carbon dioxide is detected in breath samples. The stool antigen test is another simple assay that is dependent on the detection of H. pylori antigens in stool. It is more convenient and less expensive than the urea breath test but has been slightly less accurate in some comparative studies. The urea breath test, the stool antigen test, and biopsy-based tests can all be used to assess the success of treatment. However, because these tests are dependent on H. pylori load, their use <4 weeks after treatment may lead to false-negative results. These tests are also unreliable if performed within 4 weeks of intercurrent treatment with antibiotics or bismuth compounds or within 2 weeks of the discontinuation of PPI treatment. In the assessment of treatment success, noninvasive tests are normally preferred; however, after gastric ulceration, endoscopy should be repeated to ensure healing and to exclude gastric carcinoma by further histologic sampling.

Occasionally, specialized testing such as serum gastrin and gastric acid analysis or sham feeding may be needed in individuals with complicated or refractory PUD (see “Zollinger-Ellison Syndrome,” below). Screening for aspirin or NSAIDS (blood or urine) may also be necessary in refractory H. pylori–negative PUD patients.

Date: 2014-12-21; view: 1123