Oedema

Red flags

Acute pulmonary oedema - respiratory distress, orthopnoea, frothy sputum - treat before finishing the work-up
New nephrotic-range proteinuria + oedema - risk of thrombosis (renal vein, PE) and infection
Rapidly progressive facial/periorbital oedema + haematuria in a child -> nephritic syndrome, may progress fast
Anasarca with hypotension - consider severe hypoalbuminaemia with intravascular depletion despite total-body fluid excess ("underfilled" state)
Unilateral leg swelling with pain - DVT, not a systemic oedema state - do not misattribute to heart/liver/kidney disease
Oedema + haemoptysis or acute kidney injury -> pulmonary-renal syndrome (anti-GBM, ANCA vasculitis)

By mechanism

inc capillary hydrostatic pressure - heart failure, venous insufficiency, DVT, constrictive pericarditis, renal Na+/water retention (any cause of oliguric kidney disease)
dec plasma oncotic pressure (hypoalbuminaemia) - nephrotic syndrome, cirrhosis, malnutrition, protein-losing enteropathy
inc capillary permeability - sepsis, angioedema, burns, allergic reaction
Lymphatic obstruction - malignancy, filariasis, post-surgical/radiotherapy (lymphoedema - typically non-pitting, doesn't respond to diuretics)

By distribution

Bilateral leg oedema, symmetrical, pitting - systemic cause (cardiac, renal, hepatic, hypoalbuminaemic)
Unilateral leg oedema - DVT, cellulitis, lymphatic/venous obstruction, ruptured Baker's cyst
Facial/periorbital, worse on waking - nephrotic/nephritic syndrome, angioedema, hypothyroidism
Generalised (anasarca) - severe hypoalbuminaemia, advanced heart failure, capillary leak

Onset and pattern

Rapid (days) - nephrotic/nephritic syndrome, DVT, acute heart failure, angioedema
Gradual (weeks-months) - cirrhosis, chronic heart failure, hypothyroidism, chronic venous insufficiency

Associated symptoms

Orthopnoea, PND, exertional dyspnoea -> cardiac
Frothy urine, weight gain despite reduced appetite -> nephrotic
Haematuria, oliguria, hypertension -> nephritic
Jaundice, abdominal distension, EtOH history -> hepatic
Cold intolerance, weight gain, constipation -> hypothyroid
Weight loss, PR bleeding, chronic diarrhoea -> protein-losing enteropathy/malignancy

Drugs

CCBs (esp. dihydropyridines), NSAIDs, glitazones, corticosteroids - common causes of peripheral oedema without organ failure

Pitting vs non-pitting - pitting = fluid, non-pitting = lymphoedema or myxoedema
JVP - raised in cardiac/fluid overload, normal in hypoalbuminaemic states
Ascites, hepatomegaly, spider naevi, caput medusae -> cirrhosis
Basal creps, S3, displaced apex -> heart failure
Periorbital oedema, frothy appearance suggestion -> nephrotic
Unilateral warmth/tenderness/calf swelling -> DVT (Wells score)
Signs of hypothyroidism - bradycardia, dry skin, slow-relaxing reflexes

First-line for all

Directed by suspected mechanism

Nephrotic-range proteinuria (>3.5 g/24h or PCR >300-350 mg/mmol) + hypoalbuminaemia + oedema = nephrotic syndrome -> lipid profile, renal biopsy work-up (unless clearly diabetic nephropathy), consider renal vein thrombosis if flank pain/rapid renal decline
TFT if hypothyroidism suspected
Echocardiogram if cardiac cause suspected
Doppler ultrasound if unilateral leg swelling
Liver screen + ultrasound if hepatic cause suspected

General principles

Treat the underlying cause, not just the fluid - diuretics alone in hypoalbuminaemic oedema are often only partially effective
Daily weight is the best marker of fluid balance, more reliable than examination alone

By cause

Nephrotic syndrome - salt restriction, loop diuretic +/- thiazide for resistant oedema, ACEi/ARB to reduce proteinuria, statin, consider anticoagulation if severe hypoalbuminaemia (albumin <20-25 g/L) given thrombosis risk
Cardiac oedema - loop diuretic, treat heart failure per guideline-directed therapy
Cirrhotic ascites/oedema - sodium restriction, spironolactone +/- furosemide (typically 100:40 ratio), paracentesis if tense ascites
Drug-induced (CCB) - dose reduction or switch class; adding an ACEi/ARB can reduce CCB-induced oedema
DVT - anticoagulation per usual protocol, not diuretics
Lymphoedema - compression, physiotherapy - diuretics ineffective and can cause harm (haemoconcentration)

Diuretic resistance

Check adherence to salt restriction and diuretic dosing/timing first
Sequential nephron blockade - add a thiazide/thiazide-like agent to a loop diuretic for a synergistic effect
Consider IV diuretic if gut oedema impairs oral absorption

Unilateral leg swelling treated as "fluid overload" and given diuretics - always exclude DVT/local cause before assuming systemic oedema
CCB-induced oedema is often misread as heart failure and triggers unnecessary escalation/investigation
Nephrotic syndrome oedema does not respond well to diuretics alone until proteinuria/hypoalbuminaemia are addressed - do not chase the fluid indefinitely
Severe hypoalbuminaemia can coexist with intravascular volume depletion despite visible anasarca ("underfilled") - aggressive diuresis can cause AKI/hypotension
Lymphoedema does not pit reliably and does not respond to diuretics - treating it as venous/cardiac oedema delays appropriate management
Missing thyroid function in unexplained generalised oedema - myxoedema is easily overlooked

1. Pitting or not, unilateral or bilateral

"That split tells me whether I'm dealing with a systemic fluid problem or a local one - DVT, cellulitis, lymphoedema."

2. Find the mechanism, not just treat the fluid

"Urine protein, albumin, and a BNP get me to cardiac, renal, hepatic, or hypoalbuminaemic quickly."

3. Nephrotic syndrome changes the whole plan

"Heavy proteinuria plus low albumin means I'm thinking about thrombosis risk and proteinuria-reduction, not just diuretics."

4. Match the diuretic strategy to the cause

"Cirrhotic ascites gets spironolactone-led therapy; cardiac oedema gets a loop diuretic; lymphoedema gets compression, not a diuretic at all."

5. Watch for the underfilled patient

"Visible oedema doesn't mean the intravascular space is full - I diurese cautiously in severe hypoalbuminaemia."

Study aid only. These notes are written with the help of AI. Not for guiding clinical decisions.