This is first aid book . I am prepearing for my usmle step 1 journy . Can u prepeare my concept for this topic so i can easily do uworld mcqs
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Now I have all the information needed to build a comprehensive USMLE Step 1 concept review. Let me compile the full answer.
🧠 USMLE Step 1 — Stomach Pathologies: Complete Concept Review
PART 1: GASTRITIS
Acute Gastritis
Definition: Mucosal inflammation with erosions (not full-thickness ulcers).
Key Causes & Mechanisms — memorize these for MCQs:
| Cause | Mechanism | UWorld Hook |
|---|---|---|
| NSAIDs | ↓ PGE₂ → ↓ mucus/bicarb → ↓ mucosal protection | Most tested cause; ask about RA patients on daily ibuprofen |
| Burns (Curling ulcer) | Hypovolemia → mucosal ischemia | Burn patient develops hematemesis |
| Brain injury (Cushing ulcer) | ↑ ICP → ↑ vagal tone → ↑ ACh → ↑ H⁺ production | Head trauma or brain tumor + GI bleed |
| Alcohol | Direct mucosal damage | Especially common with alcohol use disorder |
Cushing vs Curling trick: Cushing = CNS (brain) → Cushion the brain. Curling = Curling iron = Burn.
Chronic Gastritis
Core concept: Mucosal inflammation → glandular atrophy → hypochlorhydria → hypergastrinemia (feedback) → intestinal metaplasia → ↑ risk of gastric cancers.
H. pylori Gastritis (Most Common Cause of Chronic Gastritis)
- Location: Antrum first → spreads to body/corpus
- Mechanism: Urease produces NH₃ → damages mucosa; also destroys mucosal barrier
- Risks it creates:
- Peptic ulcer disease (duodenal > gastric)
- MALT lymphoma (B-cell MALToma) — H. pylori eradication can cause regression!
- Intestinal-type gastric adenocarcinoma
- Lab: Hyperchlorhydria (antral disease → ↑ gastrin release initially)
- Diagnosis: Urea breath test, stool antigen, biopsy (CLO test)
Autoimmune Gastritis
- Location: Body/fundus (corpus) — spares antrum
- Mechanism: Autoantibodies against H⁺/K⁺ ATPase (parietal cells) AND intrinsic factor
- Consequences:
- Parietal cell destruction → achlorhydria (no acid)
- ↓ Intrinsic factor → pernicious anemia (B12 deficiency)
- Achlorhydria → loss of negative feedback → ↑ gastrin → hypergastrinemia → G-cell and ECL-cell hyperplasia
- UWorld associations: Middle-aged woman, macrocytic anemia, beefy red tongue, neurologic symptoms (subacute combined degeneration)
Comparison table (MCQ favorite):
| Feature | H. pylori | Autoimmune |
|---|---|---|
| Location | Antrum → body | Body/fundus |
| Acid | ↑ (initially) then ↓ | ↓↓ (achlorhydria) |
| Gastrin | Normal/↑ | ↑↑ (hypergastrinemia) |
| Cancer risk | Adenocarcinoma, MALT | Adenocarcinoma |
| Pernicious anemia | No | Yes |
| Antibodies | Anti-CagA, etc. | Anti-parietal cell, anti-IF |
PART 2: MÉNÉTRIER DISEASE
Definition: Rare disorder of excessive TGF-α secretion → massive foveolar (surface mucous cell) hyperplasia → hypertrophied rugae that look "wavy like brain gyri."
Key features:
- Protein-losing gastropathy — protein leaks into lumen → hypoalbuminemia → edema
- Parietal cell atrophy → ↓ acid production (hypochlorhydria)
- Precancerous condition
Clinical TRIAD — "WAVEE":
- Weight loss
- Anorexia
- Vomiting
- Epigastric pain
- Edema (from protein loss/hypoalbuminemia)
Pathogenesis: Overexpression of TGF-α → binds EGF receptor → drives mucous cell proliferation
Radiology/Endoscopy: Giant rugal folds in fundus/body, "brain-like" appearance
UWorld hook: Patient with giant gastric rugae, low serum protein/albumin, peripheral edema, low gastric acid → Ménétrier disease. Don't confuse with Zollinger-Ellison (which has ↑↑ acid).
PART 3: GASTRIC CANCER
Overview
- Most common type: Gastric adenocarcinoma (>90% of gastric cancers)
- Others: Lymphoma (MALT), GI stromal tumor (GIST), carcinoid
- Presents late → poor prognosis in Western countries (<30% overall 5-year survival)
- Early symptoms mimic gastritis: dyspepsia, nausea
- Late symptoms: weight loss, abdominal pain, early satiety, anemia, GI bleed
Two Types of Gastric Adenocarcinoma
1. Intestinal Type
- Associated with: H. pylori, dietary nitrosamines (smoked/cured foods), tobacco, achlorhydria, chronic gastritis
- Location: Lesser curvature of stomach
- Gross: Bulky, ulcerated mass with raised/heaped-up margins
- Histo: Malignant glands (well-differentiated, columnar cells)
- Pathway: Normal mucosa → chronic gastritis → atrophy → intestinal metaplasia → dysplasia → cancer
- Geographic: High in Japan, Chile, Eastern Europe (dietary/environmental)
2. Diffuse Type
- Associated with: E-cadherin (CDH1) mutation — sporadic (~50% somatic CDH1 mutations) or hereditary (germline CDH1)
- NOT associated with H. pylori
- Histo: Signet ring cells — mucin-filled cells that push nucleus to periphery
- Gross: Linitis plastica — diffuse infiltration → stomach wall grossly thickened and "leather bottle"-like; rugal folds lost; no dominant mass
- Behavior: Poorly differentiated, early metastasis, worse prognosis
- Demographics: Younger age (~40 years), equal M:F
Metastatic Patterns — HIGH YIELD MCQ TABLE
| Eponym | Location | Mechanism |
|---|---|---|
| Virchow node | Left supraclavicular node | Lymphatic spread (Thoracic duct) |
| Krukenberg tumor | Bilateral ovaries | Hematogenous spread; signet ring cells |
| Sister Mary Joseph nodule | Umbilicus (subcutaneous) | Direct peritoneal spread |
| Blumer shelf | Rectouterine pouch (pouch of Douglas) | Peritoneal drop metastasis (felt on digital rectal exam) |
Paraneoplastic/Clinical Signs (UWorld favorites)
- Acanthosis nigricans — velvety hyperpigmented skin in axilla/neck; sudden onset = sign of internal malignancy
- Leser-Trélat sign — sudden appearance of multiple seborrheic keratoses → associated with gastric (and other GI) adenocarcinoma
- These are both linked to tumor production of EGF/TGF-α-like growth factors
QUICK UWorld MCQ PATTERN RECOGNITION
| Stem clue | Think |
|---|---|
| Patient on daily NSAIDs for RA, hematemesis | Acute gastritis / NSAID erosions |
| Severe burns → GI bleed | Curling ulcer (stress ulcer) |
| Head trauma, brain tumor → GI bleed | Cushing ulcer (vagal → ↑ acid) |
| Middle-aged woman, macrocytic anemia, B12 deficiency | Autoimmune (pernicious) gastritis |
| Anti-parietal cell antibodies + achlorhydria | Autoimmune gastritis → pernicious anemia |
| H. pylori + low-grade B-cell stomach lymphoma | MALT lymphoma (eradication = treatment) |
| Giant rugae + low serum protein + edema | Ménétrier disease |
| Stomach cancer + bilateral ovarian masses | Krukenberg tumor |
| Left supraclavicular node enlargement | Virchow node = GI malignancy |
| Umbilical nodule + abdominal cancer | Sister Mary Joseph nodule |
| Palpable mass on rectal exam in a woman with stomach cancer | Blumer shelf |
| "Leather bottle" stomach / linitis plastica on imaging | Diffuse gastric adenocarcinoma |
| Signet ring cells on biopsy | Diffuse type gastric adenocarcinoma |
| Stomach cancer + smoked foods + lesser curvature ulcer | Intestinal type adenocarcinoma |
| Young patient + stomach cancer + no H. pylori | CDH1 mutation (E-cadherin) → diffuse type |
| Acanthosis nigricans OR sudden seborrheic keratoses | Gastric adenocarcinoma (paraneoplastic) |
KEY PATHOGENESIS CONNECTIONS (for MCQ reasoning)
H. pylori
↓
Chronic antral gastritis
↓
Intestinal metaplasia → Intestinal-type adenocarcinoma
→ MALT (organized lymphoid tissue) → MALToma
Autoimmune attack on parietal cells
↓
↓ H⁺/K⁺ ATPase → achlorhydria
↓ Intrinsic factor → ↓ B12 absorption → pernicious anemia
↑ Gastrin (no feedback inhibition) → hypergastrinemia
→ ECL cell hyperplasia
Sources: Robbins & Kumar Basic Pathology, p. 557–558; Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 720–723
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