Gastritis
- Histological diagnosis – inflammation of the gastric mucosa
- The inflammation may be acute and predominantly neutrophilic or chronic whereby the infiltrate is composed of lymphocytes and or plasma cells
Acute gastritis
- Acute usually transient inflammatory process
- Inflammation may be accompanied by sloughing off of the mucosa which may cause a GI bleed
- Acute gastritis is frequently associated with;
- Heavy use of NSAIDs particularly asprin
- Excessive alcohol
- Heavy smoking
- Chemotherapeutic drugs
- Uraemia
- Systemic viral or bacterial infections e.g. Salmonella or CMV
- Severe stress e.g. surgery, trauma, burns
- Ischaemia and shock
- Ingestion of acid or alkali
- Gastric irradiation
- Mechanical trauma e.g. nasogastric tube
- Distal gastrectomy
- Heavy use of NSAIDs particularly asprin
Pathogenesis
- Often idiopathic
- In the settings described, the following mechanisms may be at play;
- Increase acid production
- Decreased alkali production
- Reduced blood flow
- Disruption of the mucus layer
- Direct epithelial damage
- Increase acid production
Morphology
- Grossly there may be oedema and hyperaemia, occasionally there may be haemorrhage
- Microscopically neutrophils invade the epithelium and erosion may occur whereby the epithelial lining is sloughed off
Clinical
- Findings range for being asymptomatic to minor abdominal pain to acute abdominal pain
- It is a major cause of haematemesis
Chronic gastritis
- Defined as the presence of mucosal inflammatory changes leading eventually to mucosal atrophy and epithelial metaplasia
- The epithelial changes may become dysplastic and constitute a background for the development of carcinoma
Pathogenesis
- The major aetiological associations are;
- Chronic infection with H. pylori
- Autoimmune, in association with pernicious anaemia
- Toxic as with alcohol and smoking
- Post surgical – post antrectomy bile reflux
- Motor/mechanical – obstruction and gastric atony
- Radiation
- Granulomatous conditions e.g. Crohn disease
- GvHD, amyloidosis, uraemia
- Chronic infection with H. pylori
Helicobacter pylori infection
- Most important aetiolgical association
- Link was first discovered in 1983
- S shaped gram negative rod
- H. pylori is present in 90% of patients with chronic gastritis affecting the antrum
- It colonized 50% of Americans over the age of 50
- It is also a risk factor for peptic ulcer disease, gastric adenocarcinoma and gastric lymphoma
- The specialist traits that allow the bacteria to flourish in the stomach include;
- Motility via its flagella allowing it to swim through mucus
- Urease production which produces ammonia and CO2 from urea buffering the gastric acid in the immediate vicinity of the organism
- Bacterial adhesins which bind to surface epithelial cells
- Expression of cytotoxins which act as proinflammatory peptides
- There are 2 patterns of H. pylori gastritis;
- Antral type gastritis with high acid production and elevated risk of duodenal ulcer
- Pangastritis which is followed by multifocal atrophy with lower acid production and increased risk of adenocarcinoma
- H.pylori can be diagnosed by;
- Antibody serological test
- Faecal bacterial detection
- Urea breath test – based on the generation of ammonia
- Direct bacterial visualization in the gastric mucosa
- Treatment is via antibiotic and PPI
Autoimmune gastritis
- Accounts for less than 10% of cases of chronic gastritis
- It is due to antibodies against components of parietal cells
- In the most severe cases the production of intrinsic factor is lost leading to pernicious anaemia
- It is associated with other autoimmune disorders such as Hashimoto thyroiditis,
Addison disease and type I diabetes - Patients have an increased risk of developing gastric carcinoma and endocrine tumours
Morphology
- Grossly, chronic gastritis exhibits a red boggy, coarse textured mucosa
- The distribution depends on the cause;
- H. pylori results in a variable and patchy distribution in the antrum or corpus
- Autoimmune causes produce diffuse involvement of the body and the fundus
- Histologically;
- Lymphocyte and plasma cell infiltrate in the lamina propria (may be germinal centres)
- Intraepithelial neutrophils
- Regenerative change of the surface columnar cells
- Variable mucosal gland strophy
- Metaplasia of the surface columnar epithelium to intestinal type epithelium
- Dysplasia can occur in some causes of long-standing chronic gastritis and may be severe enough to constitute carcinoma in situ
Clinical
- Usually asymptomatic although nausea, vomiting and upper abdominal discomfort can occur
- In autoimmune gastritis, there may be hypochlorhydria or achlorhydria and high levels of serum gastrin may be present. Around 10% of these patients develop pernicious anaemia
- The long term cancer risk in those with autoimmune gastritis is 2-4%