# Haemodynamic Disorders for NEET PG Pathology: Oedema, Shock, Virchow Triad, Thrombophilia, Embolism, Infarction

Source: https://tracknation.in/story/haemodynamic-disorders-for-neet-pg-pathology-oedema-shock-virchow-triad-thrombophilia-embolism-infarction (TrackNation — free UPSC notes with PYQs)

> NEET PG Pathology: the four mechanisms of oedema, hyperaemia vs congestion, petechiae to haematoma, the four types of shock, Virchow triad and red venous thrombi, factor V Leiden and other thrombophilias, pulmonary, saddle, paradoxical, fat, air and amniotic fluid embolism, decompression sickness and pulmonary infarction, with a diagram, hooks, vignette MCQs and cards.

## Start Here

🎯 **Exam priority: High.** *Expect: mechanism of oedema in a scenario, the type of shock, Virchow triad, factor V Leiden,
the source of pulmonary emboli, paradoxical and amniotic fluid embolism, and why lung infarcts are uncommon.*

CBME mapping: **PA 5.1–5.6**. Normal haemostasis and bleeding disorders are in article 14.

*Oedema, shock, Virchow triad, thrombophilia and emboli. Drawn by TrackNation.*

## Oedema

- Oedema is extra interstitial fluid — mostly water, but protein- and cell-rich with infection or lymphatic block. Four mechanisms:
**raised hydrostatic pressure** (heart failure: symmetric, dependent, pitting); **low oncotic pressure** (nephrotic syndrome,
protein-losing enteropathy, liver failure, starvation); **raised permeability** (infection, toxins, inflammation); **lymphatic
obstruction** (lymphoedema; filariasis in endemic areas, sometimes genital).

- Ascites = free fluid in the peritoneal cavity. Pulmonary oedema impairs gas exchange. Cytotoxic brain oedema (intracellular) follows
hypoxic or ischaemic injury.

## Hyperaemia, Congestion and Haemorrhage

- **Hyperaemia** (active, arterial) = more inflow; **congestion** (passive, venous) = blocked outflow.

- Haemorrhage = escape of blood from a vessel. Petechiae (pinpoint) < purpura < ecchymosis (> 2–3 cm, flat bruise); a
**haematoma** is a collection of blood outside vessels.

## Shock

Shock is failure to perfuse or oxygenate vital organs: cool clammy skin, confusion, lactate > 2 mmol/L, urine < 0.5 mL/kg/h. Hypotension
(SBP < 90 or MAP < 65) is common but not required. Cells switch to anaerobic metabolism; if shock persists, damage becomes irreversible.
In septic (distributive) shock the skin may be warm and flushed; septic shock is sepsis with hypotension or hypoperfusion despite fluids.

| **Shock type (MSD)**

 | **Mechanism**

 | **Examples**

 |
| Hypovolaemic

 | Critical loss of intravascular volume

 | Haemorrhage, fluid loss

 |
| Distributive

 | Vasodilation; blood volume normal

 | Sepsis, anaphylaxis, toxic shock, spinal injury above T4

 |
| Cardiogenic

 | Primary cardiac failure of output

 | Myocardial infarction, arrhythmia

 |
| Obstructive

 | Mechanical block to filling or emptying

 | Tension pneumothorax, cardiac tamponade

 |

## Thrombosis

- **Virchow triad**: stasis, endothelial injury, hypercoagulability. DVT begins in venous valve cusps; venous thrombi are
**red** (fibrin and red cells, few platelets). Causes: immobility, leg fractures, cancer.

- **Inherited thrombophilia**: factor V Leiden (R506Q; factor Va resists activated protein C — the commonest cause of APC
resistance), prothrombin 20210 mutation, deficiency of protein C, protein S or antithrombin, raised factors VIII, IX and XI.

## Embolism and Infarction

| **Embolus (MSD/MeSH)**

 | **Key fact**

 |
| Thromboembolus (PE)

 | Nearly all from leg or pelvic vein DVT; higher risk at popliteal level or above

 |
| Saddle

 | Lodges at the bifurcation of the main pulmonary artery

 |
| Paradoxical

 | Venous clot crosses to the arterial side via ASD or patent foramen ovale → stroke

 |
| Fat

 | After fractures of large bones, or corticosteroids

 |
| Air

 | After trauma, surgery or pressure change

 |
| Amniotic fluid

 | Hypoxia, hypotension, coagulopathy; a leading cause of sudden death in labour

 |
| Decompression (caisson disease, the bends)

 | Nitrogen bubbles on rapid ascent; joints and circulation; recompression

 |

**Infarction** is necrosis from local ischaemia, usually a thrombus or embolus. Pulmonary infarcts appear as pleural-based wedges
but are uncommon because the lung has a dual (bronchial and pulmonary) supply. A negative D-dimer makes PE very unlikely when pre-test probability is low.

## Traps the Examiner Sets

- Nephrotic or liver failure oedema = low oncotic pressure; heart failure = high hydrostatic pressure.

- Septic shock is distributive (warm skin early); tamponade is obstructive.

- Pulmonary emboli come from leg/pelvic veins; paradoxical emboli need a right-to-left shunt.

- Lung infarcts are rare: dual blood supply.

## Memory Hooks & Shortcuts

*Shortcuts to lock in this article's numbers and lists. Each one only re-packages facts proven above.*

- 🧠 **Pump, Pipe, Plasma, Plumbing** — hydrostatic, permeability, oncotic, lymphatic oedema

- 🧠 **HDCO: Hole (volume lost), Dilated, Can't pump, Obstructed** — four shock types

- 🧠 **Virchow's SEH: Stasis, Endothelium, Hypercoagulable** — Virchow triad

- 🧠 **Leiden Leaves Va alone (APC can't cut it)** — factor V Leiden

- 🧠 **Paradox needs a Passage (PFO/ASD)** — paradoxical embolism

- 🧠 **FAT after Femur, AIR after Ascent** — fat and gas emboli

- 🧠 **Two pipes save the lung** — dual blood supply

## Rapid-Revision Cards

- ↑ hydrostatic, ↓ oncotic, ↑ permeability, lymphatic block.

- Low oncotic pressure.

- Symmetric, dependent, pitting — high hydrostatic.

- Lymphoedema, sometimes genital.

- Intracellular; hypoxia/ischaemia.

- Active inflow vs passive outflow block.

- > 2–3 cm flat bleed.

- Hypovolaemic, distributive, cardiogenic, obstructive.

- Vasodilation, normal volume — sepsis, anaphylaxis, neurogenic.

- Tamponade, tension pneumothorax.

- Lactate > 2; urine < 0.5 mL/kg/h; SBP < 90 or MAP < 65.

- Stasis, endothelial injury, hypercoagulability.

- Red; valve cusps; few platelets.

- R506Q; APC resistance.

- Leg/pelvic DVT.

- Pulmonary artery bifurcation.

- ASD/PFO → stroke.

- Large-bone fractures.

- Hypoxia, hypotension, coagulopathy in labour.

- Nitrogen bubbles; recompression.

- Dual blood supply.

## Sources

*Facts in this article were checked against these documents.*

- MSD Manual Professional: Edema; Shock; Deep Venous Thrombosis; Pulmonary Embolism — Merck & Co. (MSD Manuals), reviewed 2025–26 (link)

- MSD Manual Professional: Amniotic Fluid Embolism; Decompression Sickness; Overview of Thrombotic Disorders — Merck & Co. (MSD Manuals), reviewed 2025–26 (link)

- Medical Subject Headings (MeSH) scope notes — US National Library of Medicine, accessed 2026 (link)

- Competency Based Undergraduate Curriculum, Pathology (PA 5) — National Medical Commission, 2024

## Test Yourself: Practice Questions

Thirty questions in NEET PG style, most of them clinical vignettes.

## Practice Questions (NEET PG pattern)

*Original questions written in the style of the exam: +4 for a correct answer, −1 for a wrong one. Every answer
was checked against the sources listed above. NEET PG papers are not published by NBEMS, so these are not past-paper questions.*

**Q1.** A child with nephrotic syndrome has generalised oedema. The main mechanism is

- (a) increased capillary permeability from infection

- (b) low plasma oncotic pressure

- (c) lymphatic obstruction

- (d) raised capillary hydrostatic pressure

**Answer: (b)** — Also liver failure, protein-losing enteropathy, starvation.

**Q2.** A man with right heart failure has symmetric, dependent, painless, pitting leg oedema. The mechanism is

- (a) raised capillary hydrostatic (venous) pressure

- (b) lymphatic obstruction

- (c) allergic permeability

- (d) low oncotic pressure

**Answer: (a)** — MSD oedema table.

**Q3.** A man from a filaria-endemic area has long-standing swelling of one leg and the scrotum. The mechanism is

- (a) venous thrombosis

- (b) low oncotic pressure

- (c) right heart failure

- (d) lymphatic obstruction (lymphoedema)

**Answer: (d)** — Initially pitting, later fibrotic.

**Q4.** Oedema fluid that is rich in protein and cells points to

- (a) nephrotic syndrome

- (b) infection or lymphatic obstruction

- (c) starvation

- (d) heart failure

**Answer: (b)** — Ordinary oedema fluid is mostly water.

**Q5.** After a severe hypoxic-ischaemic insult, the brain swells from fluid inside the cells. This is

- (a) vasogenic oedema only

- (b) cytotoxic brain oedema from hypoxic-ischaemic injury

- (c) lymphoedema

- (d) hydrocephalus

**Answer: (b)** — MeSH.

**Q6.** Increased blood in an organ because venous outflow is obstructed is called

- (a) active hyperaemia

- (b) passive (venous) congestion

- (c) infarction

- (d) haemorrhage

**Answer: (b)** — Active hyperaemia = more arterial inflow.

**Q7.** A flat purplish skin bleed larger than 2–3 cm is called

- (a) a petechia

- (b) purpura simplex only

- (c) an ecchymosis

- (d) a haematoma

**Answer: (c)** — Larger than petechiae and purpura.

**Q8.** A collection of blood outside blood vessels, within a tissue or space, is a

- (a) embolus

- (b) petechia

- (c) thrombus

- (d) haematoma

**Answer: (d)** — MeSH.

**Q9.** A patient with pneumonia has hypotension despite adequate fluids, warm flushed skin and a bounding pulse. The shock type is

- (a) hypovolaemic

- (b) obstructive

- (c) distributive (septic)

- (d) cardiogenic

**Answer: (c)** — Vasodilation with normal blood volume.

**Q10.** Distributive shock differs from hypovolaemic shock because

- (a) the heart fails as a pump

- (b) blood volume is lost

- (c) blood volume is normal but vessels are dilated

- (d) great vessels are blocked

**Answer: (c)** — Sepsis, anaphylaxis, toxic shock, spinal injury above T4.

**Q11.** After a large myocardial infarction, a patient develops shock from failure of cardiac output. The shock type is

- (a) obstructive

- (b) cardiogenic

- (c) distributive

- (d) hypovolaemic

**Answer: (b)** — Primary cardiac failure of output.

**Q12.** A trauma patient is in shock caused by cardiac tamponade. The shock type is

- (a) hypovolaemic

- (b) obstructive

- (c) cardiogenic

- (d) distributive

**Answer: (b)** — Also tension pneumothorax.

**Q13.** A patient with a high spinal cord injury (above T4) becomes hypotensive. The shock is

- (a) obstructive

- (b) cardiogenic

- (c) neurogenic — a form of distributive shock

- (d) hypovolaemic always

**Answer: (c)** — MSD classifies it as distributive.

**Q14.** A laboratory marker of tissue hypoperfusion in shock is a blood lactate above

- (a) 10 mmol/L

- (b) 20 mmol/L

- (c) 0.5 mmol/L

- (d) 2.0 mmol/L

**Answer: (d)** — Also oliguria < 0.5 mL/kg/h.

**Q15.** Hypotension in shock is usually defined as

- (a) systolic < 90 mm Hg or mean arterial pressure < 65 mm Hg

- (b) systolic < 120

- (c) diastolic < 80

- (d) mean arterial pressure < 100

**Answer: (a)** — Common but not required for shock.

**Q16.** Septic shock is defined as sepsis with

- (a) hypotension or hypoperfusion despite adequate fluid resuscitation

- (b) a raised white count

- (c) fever alone

- (d) bacteraemia alone

**Answer: (a)** — Lactic acidosis, oliguria, confusion.

**Q17.** The three factors of Virchow's triad are

- (a) fever, pain and swelling

- (b) anaemia, jaundice and splenomegaly

- (c) stasis, endothelial injury and hypercoagulability

- (d) hypertension, diabetes and smoking

**Answer: (c)** — MSD DVT page.

**Q18.** An immobilised patient after a leg fracture develops a calf DVT. The thrombus is typically

- (a) red — fibrin and red cells with few platelets, starting at valve cusps

- (b) made of fat

- (c) infected

- (d) white — platelets only

**Answer: (a)** — Immobility and leg fracture are classic causes.

**Q19.** A young woman with recurrent DVT has a mutation that makes activated factor V resistant to activated protein C. This is

- (a) prothrombin 20210 mutation

- (b) haemophilia

- (c) factor V Leiden (R506Q)

- (d) antithrombin deficiency

**Answer: (c)** — The commonest cause of APC resistance.

**Q20.** Which of these is an inherited cause of venous thrombosis listed by MSD?

- (a) protein C or protein S deficiency

- (b) vitamin K deficiency

- (c) haemophilia A

- (d) von Willebrand disease

**Answer: (a)** — Also antithrombin deficiency and prothrombin 20210.

**Q21.** Nearly all pulmonary emboli arise from

- (a) the portal vein

- (b) the left atrium

- (c) deep vein thrombi in the legs or pelvis

- (d) arm veins

**Answer: (c)** — Risk higher if the thrombus reaches the popliteal vein or above.

**Q22.** A large embolus is found straddling the bifurcation of the main pulmonary artery. This is a

- (a) fat embolus

- (b) paradoxical embolus

- (c) saddle embolus

- (d) air embolus

**Answer: (c)** — MSD.

**Q23.** A man with a leg DVT suddenly has a stroke. Echocardiography shows a patent foramen ovale. This is

- (a) paradoxical embolism

- (b) fat embolism

- (c) septic embolism

- (d) air embolism

**Answer: (a)** — Venous clot reaches arterial side through a right-to-left defect.

**Q24.** After a fracture of a large bone, a patient develops an embolus that is not a blood clot. The classic type is

- (a) air embolism

- (b) tumour embolism

- (c) amniotic fluid embolism

- (d) fat embolism

**Answer: (d)** — Also after corticosteroids (MeSH).

**Q25.** During labour, a woman suddenly develops hypoxia, hypotension and bleeding from a coagulopathy. The likely cause is

- (a) amniotic fluid embolism

- (b) pulmonary thromboembolism

- (c) placenta praevia

- (d) eclampsia

**Answer: (a)** — Fetal antigens enter maternal blood; a leading cause of sudden death in labour.

**Q26.** A diver who surfaced rapidly develops severe joint pain and confusion. The cause and treatment are

- (a) fat embolism — steroids

- (b) air in the pleura — chest drain

- (c) hypoglycaemia — glucose

- (d) nitrogen bubbles from rapid decompression — recompression therapy

**Answer: (d)** — Decompression sickness (caisson disease, the bends).

**Q27.** Air embolism usually follows

- (a) large-bone fractures

- (b) labour

- (c) DVT

- (d) trauma, surgery or changes in atmospheric pressure

**Answer: (d)** — MeSH.

**Q28.** Pulmonary infarction is uncommon after pulmonary embolism because

- (a) the lung has no veins

- (b) emboli always dissolve

- (c) the lung has a dual blood supply (bronchial and pulmonary)

- (d) lung tissue does not need oxygen

**Answer: (c)** — When it happens, it is a pleural-based wedge.

**Q29.** An infarct is

- (a) fluid in tissues

- (b) a collection of blood outside vessels

- (c) necrosis from local ischaemia, usually due to a thrombus or embolus

- (d) a type of shock

**Answer: (c)** — MeSH.

**Q30.** In an outpatient with low pre-test probability of PE, a negative D-dimer

- (a) means DVT is present

- (b) makes pulmonary embolism very unlikely

- (c) is useless

- (d) confirms PE

**Answer: (b)** — Below 0.4 mcg/mL.

### Active Recall

From memory: give the four mechanisms of oedema with an example each; distinguish hyperaemia and congestion; classify the four types of shock with causes and markers; state Virchow triad and the inherited thrombophilias; and describe pulmonary, saddle, paradoxical, fat, air and amniotic fluid emboli, decompression sickness and why lung infarcts are uncommon.