A 56-year-old man comes to the office for upper abdominal pain occurring with meals for the last month. His symptoms improve when fasting. The patient's other medical problems are coronary artery disease and osteoarthritis. His medications include aspirin, simvastatin, and acetaminophen as needed. The patient drinks 1 or 2 beers daily but does not use tobacco or illicit drugs. Upper endoscopy is performed and reveals a gastric ulcer with a smooth, rounded border and an exudative base. A biopsy of the ulcer is taken and placed into a urea-containing solution that includes phenol red, a pH indicator. Thirty minutes later, the solution has turned pink, indicating a pH increase. This test result suggests that which of the following processes is occurring?

Question

A 56-year-old man comes to the office for upper abdominal pain occurring with meals for the last month.  His symptoms improve when fasting.  The patient's other medical problems are coronary artery disease and osteoarthritis.  His medications include aspirin, simvastatin, and acetaminophen as needed.  The patient drinks 1 or 2 beers daily but does not use tobacco or illicit drugs.  Upper endoscopy is performed and reveals a gastric ulcer with a smooth, rounded border and an exudative base.  A biopsy of the ulcer is taken and placed into a urea-containing solution that includes phenol red, a pH indicator.  Thirty minutes later, the solution has turned pink, indicating a pH increase.  This test result suggests that which of the following processes is occurring?

Quizplus · Accepted Answer

11ec160b_395a_1906_9249_49a36319bc53_MD0001_00 Helicobacter pylori infection is a common cause of peptic ulcers. During endoscopy, biopsy specimens are often obtained for direct tissue diagnosis. In contrast to the time-intensive task of culturing the bacteria, the rapid urease test can be used to quickly diagnose an active infection. The rapid urease test is an indirect test for H pylori and relies on the bacterial production of the enzyme urease, which splits gastric urea into ammonia and CO₂. Ammonia production increases the local pH and allows the bacteria to survive in the acidic stomach environment. Biopsy specimens are evaluated in the presence of urea and a pH indicator; evidence of alkalinization (due to active ammonia formation) confirms active H pylori infection. Phenol red is a common reagent that changes from yellow to pink in the presence of an alkaline pH. (Choice A) Gastric adenocarcinoma (ie, clonal proliferation of glandular cells) can present as a gastric ulcer; therefore, gastric ulcers should be biopsied to rule out malignancy. However, malignant ulcers do not cause a color change on urease testing. (Choice B) Nonsteroidal anti-inflammatory drugs (NSAIDS) (eg, aspirin, ibuprofen) are another common cause of peptic ulcers due to their inhibition of the enzyme cyclooxygenase, which is responsible for the synthesis of gastroprotective prostaglandins. However, urease would not be present in an NSAID-induced ulcer. (Choice D) Zollinger-Ellison syndrome is due to gastrin hypersecretion, leading to overproduction of gastric acid and peptic ulcer formation. However, the ulcers would not produce a color change on urease testing. (Choice E) Autoimmune gastritis is due to T-cell mediated destruction of parietal cells. Patients are typically asymptomatic, but prolonged disease leads to pernicious anemia (B12 deficiency due to intrinsic factor destruction) characterized by megaloblastic anemia and neurologic dysfunction. Gastric pH is increased due to loss of parietal cells, but ulcers do not occur in this condition. Educational objective: Helicobacter pylori produces the enzyme urease, which splits urea into CO₂ and ammonia and neutralizes the local acidic gastric pH. Active infection can be confirmed through rapid urease testing, in which gastric mucosa is evaluated in the presence of urea and a pH indicator. Evidence of alkalization (due to ammonia formation) is confirmatory. __________ References: Diagnosis of Helicobacter pylori using the rapid urease test. (http://www.ncbi.nlm.nih.gov/pubmed/25705641)

A 56-Year-Old Man Comes to the Office for Upper Abdominal