🩸 Anaemias Linked to Stomach Disorders — Simplified for MSRA

examiner mla
Oct 10
3 min read

Understanding how different stomach disorders cause specific types of anaemia is essential for exam reasoning and real-life clinical work.This post explains how gastric anatomy and cell function relate to iron and vitamin B₁₂ absorption, and how disease in each region leads to characteristic anaemias.

🧭 The Gastric Map

Region	Main Function	Key Secretions
Cardia	Mucus protection	Mucus
Fundus & Body	Acid and Intrinsic Factor production	Parietal cells → HCl & IF; Chief cells → pepsinogen
Antrum	Acid regulation via hormones	G cells → gastrin; D cells → somatostatin
Duodenum (beyond stomach)	Iron absorption (Fe²⁺ form)	—

🧠 Core concept:

Fundus/body → Vitamin B₁₂ (via Intrinsic Factor)

Acidic environment → Iron absorption Duodenum → Iron uptake site

🧫 Types of Anaemia by Gastric Pathology

1️⃣ Pernicious Anaemia — Vitamin B₁₂ Deficiency

Mechanism

Autoimmune destruction of parietal cells (in fundus + body) causes:

↓ Intrinsic Factor → vitamin B₁₂ cannot bind and be absorbed in terminal ileum
↓ Hydrochloric acid (achlorhydria) → impaired conversion of Fe³⁺ → Fe²⁺ → ↓ iron uptake

Therefore:➡️ Primary anaemia: Megaloblastic (vitamin B₁₂ deficiency)

➡️ Possible secondary: Iron-deficiency (from achlorhydria)

Stage	Dominant Defect	Likely Anaemia
Early	Acid loss (achlorhydria)	Mild iron-deficiency
Late	Intrinsic Factor loss	Classic B₁₂ deficiency
Chronic	Both	Mixed / dimorphic picture

Key Features

Macrocytosis, glossitis, paresthesia, posterior-column neuropathy
Anti-Intrinsic Factor & anti-parietal cell antibodies positive
Low B₁₂, high MCV, raised methylmalonic acid + homocysteine

MSRA Pearl:

Vitamin B₁₂ deficiency is defining; iron deficiency may coexist but never dominates.

2️⃣ Iron-Deficiency Anaemia

Mechanisms

↓ acid production → less Fe³⁺ → Fe²⁺ conversion
Chronic micro-bleeding (ulcers, erosive gastritis, H. pylori)
Partial gastrectomy → loss of acid-secreting mucosa

Region: Antrum ± bodyAnaemia Type: Microcytic, hypochromicTypical clues: Fatigue, glossitis, spoon nails, low ferritin, ↑ TIBC

3️⃣ Post-Gastrectomy Anaemia (Combined Type)

After partial/total gastrectomy:

Loss of acid → ↓ iron absorption (duodenum needs Fe²⁺)
Loss of Intrinsic Factor → ↓ B₁₂ absorption

Sequence

Early → Iron deficiency
Late → Vitamin B₁₂ deficiencyOverall: Mixed (micro → macro) anaemia

Region Lost	Consequence
Fundus + Body	↓ HCl + ↓ IF
Pylorus bypass	↓ Iron absorption

4️⃣ Chronic Gastritis Patterns

Type	Region	Anaemia	Mechanism
Antral-predominant (H. pylori)	Antrum	Iron-deficiency	Hypochlorhydria + microbleeds
Corpus-predominant (atrophic)	Body + Fundus	B₁₂-deficiency	Parietal-cell loss → ↓ IF
Pan-gastritis	Entire stomach	Mixed (Fe + B₁₂)	Diffuse mucosal damage

⚖️ Summary Table

Condition	Region Affected	Mechanism	Anaemia Type
Autoimmune (Pernicious) Gastritis	Fundus + Body	↓ IF → ↓ B₁₂ absorption ± achlorhydria → ↓ Fe	Megaloblastic ± Iron-def.
H. pylori Gastritis	Antrum ± Body	Hypochlorhydria / blood loss	Iron-deficiency
Gastrectomy / Bypass	Fundus + Body removed	↓ acid + ↓ IF → ↓ Fe + ↓ B₁₂	Mixed
Gastric Cancer / Ulcers	Any	Chronic blood loss	Iron-deficiency

🩺 Clinical Pearls for MSRA

MCV clues:↓ MCV → Iron deficiency ↑ MCV → B₁₂/Folate deficiency Mixed MCV → Combined defects
Autoimmune gastritis = both achlorhydria and IF loss → B₁₂ deficiency hallmark + possible iron loss.
Post-gastrectomy: always supplement iron + B₁₂.
Check antibodies when macrocytosis + neuropathy → Pernicious anaemia.

🧩 Mnemonics & Revision Aid

Letter	Region	Anaemia
B	Body/Fundus	B₁₂ deficiency
I	Infection (H. pylori)	Iron deficiency
D	Duodenum bypassed	Dual (Fe + B₁₂)

🧠 Mnemonic: “B → B₁₂, I → Iron, D → Dual.”

✨ Final Take-Home Summary

Parietal cells make both HCl and Intrinsic Factor.
Loss of HCl → reduced iron absorption, while loss of IF → vitamin B₁₂ deficiency.
In autoimmune gastritis (pernicious anaemia), both are lost, but vitamin B₁₂ deficiency dominates because IF loss causes complete malabsorption, whereas acid loss only partially impairs iron uptake.
Over time, some patients develop a mixed picture with both macrocytic and microcytic features.

🩺 In Plain Words

“The upper part of the stomach makes acid and a substance called Intrinsic Factor.If that area is damaged, acid loss reduces iron absorption, and loss of Intrinsic Factor stops vitamin B₁₂ from being absorbed.That’s why some patients develop both iron and B₁₂ deficiency, but the B₁₂ deficiency is usually more severe and defines pernicious anaemia.”

🔖 Quick Reference Table

Stomach Region	Main Secretions	Nutrient Affected	Anaemia Result
Fundus + Body	HCl + Intrinsic Factor	Iron & B₁₂	Megaloblastic ± Iron
Antrum	Gastrin / Somatostatin	Acid regulation	Iron deficiency
Duodenum	—	Iron absorption site	Iron deficiency if bypassed

✅ Key MSRA Insight:Always link the site of pathology to the type of anaemia:

Fundus / Body → B₁₂ (Intrinsic Factor)
Antrum / Acid → Iron (pH-dependent)
Post-Gastrectomy → Both