[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Lung](https://durgical.com/en/general-pathology/areas/lung/) › Pulmonary edema: hemodynamic vs alveolar-capillary injury

# Pulmonary edema: hemodynamic vs alveolar-capillary injury

- Lesion

Fluid fills the lung either because pressure in the pulmonary veins is high (heart failure) or because the alveolar wall is damaged and leaks.

Updated Nov 12, 2026

## Key points

- Commonest cause: left-sided heart failure raising pulmonary venous pressure; it starts at the lung bases (dependent edema).
- Heart failure cells: alveolar macrophages full of hemosiderin from small hemorrhages.
- Long-standing congestion (mitral stenosis) gives brown induration: firm, brown, fibrotic lungs.
- Injury edema: pneumonia, aspiration, inhaled toxins, sepsis, trauma, transfusion, drugs; it is an exudate.
- High-altitude and neurogenic edema are of mixed or uncertain mechanism.

## What it is

Pulmonary edema is extra fluid in the interstitium and then the alveoli. Hemodynamic (cardiogenic) edema is a protein-poor transudate pushed out by high pressure, most often from left heart failure. Injury (noncardiogenic) edema is a protein-rich exudate from damaged endothelium or epithelium, and in its severe form it is the lesion of ARDS. In both cases the lungs are heavy and wet.

## Structure

- Gross: heavy, wet lungs that ooze frothy, sometimes blood-tinged fluid when cut.
- Hemodynamic edema (H&E): engorged alveolar capillaries and pale pink, finely granular transudate filling the alveoli.
- Chronic congestion: many hemosiderin-laden macrophages (golden-brown, Prussian blue positive) and thickened, fibrotic septa.
- Injury edema: protein-rich exudate with inflammatory cells and, when severe, hyaline membranes.

## Step by step

- The left ventricle fails, pressure rises in the left atrium and pulmonary veins.
- Capillary hydrostatic pressure exceeds the oncotic pressure that holds fluid in.
- Fluid first fills the interstitium; lymphatics drain it until they are overwhelmed.
- The interstitium widens (Kerley lines) and then fluid floods the alveoli, beginning at the bases.
- Flooded alveoli cannot exchange gas, causing hypoxaemia and dyspnoea; the wet lung also favours infection.
- When endothelium or epithelium is injured instead, protein leaks out even at normal pressure.

## Hemodynamic vs injury pulmonary edema

| Feature | Hemodynamic (cardiogenic) | Injury (noncardiogenic) |
| --- | --- | --- |
| [Main cause](https://durgical.com/en/conditions/heart-failure/) | Left heart failure, volume overload | Sepsis, pneumonia, aspiration, trauma, toxins |
| [Fluid](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/) | Transudate, little protein | Exudate, rich in protein |
| Distribution | Bases first, dependent | Diffuse, patchy |
| Microscopy | Pale pink fluid, congested capillaries, heart failure cells | Exudate, inflammation, hyaline membranes |
| Pulmonary capillary pressure | High | Normal |

## Clinical notes

- Acute cardiogenic edema: orthopnoea, paroxysmal nocturnal dyspnoea, crackles, pink frothy sputum.
- Heart failure cells in sputum or lavage point to chronic venous congestion.
- A normal wedge pressure with bilateral infiltrates suggests injury edema (ARDS).

## Memory aid

Pressure pushes plain water; injury leaks protein.

## Test yourself

Think of the answer, then tap the question to see it.

## What are heart failure cells and where are they found?

Alveolar macrophages filled with hemosiderin from small hemorrhages, seen in the alveoli in chronic pulmonary venous congestion.

## Why does cardiogenic edema start at the lung bases?

Hydrostatic pressure is highest in the dependent parts of the lung, so fluid leaks there first.

## What is brown induration of the lung?

Firm, brown lungs from long-standing congestion: abundant hemosiderin-laden macrophages and septal fibrosis, classically in mitral stenosis.

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## Elsewhere in DurgiPedia

- [Physiology of pulmonary edema](https://durgical.com/en/physiology/physiology-of-pulmonary-edema/)

## Connections

## Related 4

- [Edema and effusions: the four mechanisms](https://durgical.com/en/general-pathology/edema-and-effusions-the-four-mechanisms/)
- [Hyperemia and congestion (the nutmeg liver, heart-failure cells)](https://durgical.com/en/general-pathology/hyperemia-and-congestion/)
- [Diffuse alveolar damage (ARDS)](https://durgical.com/en/general-pathology/diffuse-alveolar-damage/)
- [Atelectasis: resorption, compression and contraction](https://durgical.com/en/general-pathology/atelectasis-resorption-compression-and-contraction/)

## Related conditions 3

- [Heart failure](https://durgical.com/en/conditions/heart-failure/)
- [High-altitude illness (AMS, HACE, HAPE)](https://durgical.com/en/conditions/high-altitude-illness/)
- [Drowning](https://durgical.com/en/conditions/drowning/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Lung Diseases](https://medlineplus.gov/lungdiseases.html) (MedlinePlus, US National Library of Medicine, 2025); [Acute Respiratory Distress Syndrome](https://www.ncbi.nlm.nih.gov/books/NBK436002/) (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/pulmonary-edema-hemodynamic-vs-alveolar-capillary-injury/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/pulmonary-edema-hemodynamic-vs-alveolar-capillary-injury/