Helicobacter Pylori and Cancers of the Stomach (Video Part 2)

SMLE Anatomy #12

Helicobacter pylori is a urease-positive bacteria that can be stained with the silver stain. H. pylori infection increases the risk of peptic ulcers, intestinal-type stomach adenocarcinoma, and MALT lymphomas.

There are two subtypes of stomach cancers: 1) intestinal-type that is associated with H. pylori infection, autoimmune gastritis, dietary nitrosamines (smoked foods), and blood type A; this type of stomach cancer commonly affects the lesser curvature of the stomach and  presents with large ulcers with heaped margins, and 2) Diffuse-type, which is characterized by signet ring cells and linitis plastica (thick, leathery stomach wall); this type of stomach cancer is NOT associated with H. pylori infection or dietary nitrosamines.

Zollinger-Ellison syndrome, which is a common cause of duodenal ulcer, is a gastrin-producing tumor in the duodenum or pancreas that increases gastric acid secretion. Consequently, Brunner’s glands which are located in the duodenal submucosa undergo hypertrophy to increase the secretion of alkaline mucus. Another unique feature of Zollinger-Ellison syndrome is thickening of the gastric folds.

Several different classes of drugs are used for the treatment of peptic ulcer disease:

[[ Antacids ]]
Magnesium hydroxide – can cause diarrhea (Maximum fecal output)
Aluminum hydroxide – can cause constipation (Minimum fecal output)
Calcium carbonate – interferes with absorption of tetracyclines

[[ Histamine H2 antagonists ]]
Cimetidine, ranitidine, famotidine, nizatidine
Cimetidine side effects: antiandrogenic, inhibit P-450, ↑serum creatinine

[[ Proton pump inhibitors ]]
Omeprazole, lansoprazole, esomeprazole, pantoprazole, dexlansoprazole
Adverse reactions include pneumonia, hypomagnesemia, hip fractures, and risk of C. difficile infection.

[[ Mucosal protective agents ]]
Sucralfate and bismuth form a protective coating over ulcer beds
Misoprostol (PGE1) increase production of mucus barrier and decrease production of gastric acid

[[ Antibiotics ]]
Macrolides, metronidazole, clarithromycin, and tetracyclines for the treatment of H. pylori. Triple therapy for H. pylori consists of a combination of two antibiotics and a proton pump inhibitor.


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USMLE Step 1 Practice Questions

Question: How does Helicobacter pylori infection increase the risk of MALT lymphoma?
Answer: MALT lymphoma is a B-cell non-Hodgkin lymphoma that is found at extra-nodal sites such as the stomach. H. pylori infection irritates the mucosal lining of the stomach, as a consequence of which MALT-type lymphoid tissue develops as part of the inflammatory reaction. Continuous stimulation of these lymphomas induce constant replication of B-lymphocytes that are at increased risk of replication error (mutation) that can lead to lymphoma.
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