Oedema: Causes, Types and Treatment Methods

What Is Oedema?

Hello, I am Dr. Emre Gecer. Oedema is swelling caused by an abnormal accumulation of fluid in the interstitial (between-cell) tissue. The fluid distribution in our body is normally maintained by a delicate balance between blood inside the vessels and the fluid in the surrounding tissue. When this balance is disrupted, fluid leaks out of the vessels and oedema results.

Oedema is not a disease in its own right but a symptom of an underlying condition. It can be due to harmless causes (prolonged standing, hot weather) or it can signal serious disease such as heart failure, kidney disease or deep vein thrombosis. Identifying the cause of oedema is therefore very important.

How Does Oedema Form? Starling Forces

The exchange of fluid between intravascular and interstitial spaces is governed by the Starling forces. Four key factors maintain this balance:

• Capillary hydrostatic pressure: Blood pressure inside the vessels pushes fluid out (an increase favours oedema)
• Interstitial hydrostatic pressure: Pressure within the tissue opposes fluid leaving the vessels
• Plasma oncotic pressure: Plasma proteins (especially albumin) create an osmotic force holding fluid in the vessels (a decrease favours oedema)
• Interstitial oncotic pressure: Proteins in the tissue draw fluid out of the vessels

The mechanisms by which oedema forms fall mainly into four groups:

• Raised capillary hydrostatic pressure: Heart failure, venous insufficiency, DVT
• Reduced plasma oncotic pressure: Hypoalbuminaemia (nephrotic syndrome, liver cirrhosis, malnutrition)
• Increased capillary permeability: Inflammation, allergy, sepsis, burns
• Impaired lymphatic drainage: Lymphoedema (surgery, radiotherapy, filariasis)

Types of Oedema

1. Peripheral Oedema

The most common type of oedema. Presents as swelling in the legs, ankles and feet. Worsens through the day under the effect of gravity and tends to improve by morning. In bed-bound patients it appears in the sacral (lower back) area.

2. Pulmonary Oedema

Fluid accumulation in lung tissue. A life-threatening emergency. Left heart failure is the most common cause. Presents with sudden dyspnoea, orthopnoea (worse when lying down), cough, pink frothy sputum and wheezy breathing. Requires emergency treatment.

3. Cerebral Oedema

Fluid accumulation in brain tissue. Can occur with head trauma, stroke, brain tumour, hyponatraemia or high-altitude sickness. Presents with headache, nausea, vomiting, altered consciousness and papilloedema. Requires urgent neurological intervention.

4. Macular Oedema

Fluid accumulation in the macular region of the retina. Can occur in diabetic retinopathy, retinal vein occlusion and after intra-ocular surgery. Causes central vision loss.

5. Generalised Oedema — Anasarca

Massive, widespread fluid accumulation throughout the body. Usually seen in severe systemic disease such as advanced heart failure, nephrotic syndrome or end-stage liver cirrhosis.

Pitting versus Non-Pitting Oedema

One of the most important distinctions in the physical examination of oedema is between pitting (which leaves an indentation) and non-pitting oedema.

Pitting Oedema

When pressure is applied to the swollen area with a finger for 10–15 seconds, a pit forms and slowly resolves. This indicates that fluid is moving freely in the interstitial space.

• Heart failure
• Kidney disease (nephrotic syndrome, nephritic syndrome)
• Liver cirrhosis
• Deep vein thrombosis
• Venous insufficiency
• Drug-induced oedema

Grading:

• +1: Mild pit (2 mm), resolves immediately
• +2: Moderate pit (4 mm), resolves in 15 seconds
• +3: Deep pit (6 mm), takes more than 30 seconds
• +4: Very deep pit (8 mm), takes more than 2 minutes

Non-Pitting Oedema

No pit forms under pressure. The tissue feels firm or doughy.

• Lymphoedema: Lymphatic obstruction or damage (mastectomy, radiotherapy, filariasis)
• Myxoedema: Due to severe hypothyroidism, from mucopolysaccharide deposition (particularly on the pretibial surface and the face)
• Lipoedema: Abnormal distribution of adipose tissue (symmetrical in the lower limbs)

Main Causes of Oedema

Cardiac Causes

Heart failure is the most important systemic cause of oedema. When the heart's pumping function declines, venous pressure rises and fluid leaks out of the vessels. Right heart failure typically produces peripheral oedema (legs, abdominal ascites); left heart failure produces pulmonary oedema. Accompanying symptoms include dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea, exercise intolerance and fatigue.

Renal Causes

• Nephrotic syndrome: Excessive loss of protein (especially albumin) through the kidneys causes hypoalbuminaemia and a fall in oncotic pressure. Widespread, marked oedema (including facial), frothy urine and hyperlipidaemia are characteristic
• Acute glomerulonephritis: Oedema from sodium and water retention; accompanied by hypertension and haematuria
• Chronic kidney disease: As GFR falls, excretion of fluid and sodium declines

Hepatic Causes

Liver cirrhosis causes oedema both by reducing albumin production (lowering oncotic pressure) and by producing portal hypertension (raising splanchnic venous pressure). Ascites (intra-abdominal fluid accumulation) and lower-limb oedema are typical.

Venous Causes

• Deep vein thrombosis (DVT): Usually unilateral leg swelling, pain, redness and warmth. Requires urgent assessment because of the risk of pulmonary embolism
• Chronic venous insufficiency: Venous valve dysfunction; bilateral lower-limb oedema, varicose veins, skin changes (haemosiderin deposition, stasis dermatitis)

Lymphoedema

Obstruction or damage to the lymphatic system causes high-protein fluid to accumulate in the tissue. Can be primary (congenital lymphatic malformation) or secondary (surgery, radiotherapy, infection). Usually presents as unilateral, non-pitting, progressive swelling.

Drug-Induced Oedema

• Calcium-channel blockers (amlodipine most commonly)
• NSAIDs (ibuprofen, naproxen)
• Corticosteroids
• Thiazolidinediones (pioglitazone)
• Gabapentin, pregabalin
• Oestrogen-containing oral contraceptives

Oedema in Pregnancy

Mild ankle oedema in pregnancy is physiological and common. However, when sudden, widespread oedema (particularly of the face and hands) appears together with hypertension and proteinuria, pre-eclampsia must be considered and assessed urgently.

Diagnostic Approach

A comprehensive assessment is needed to identify the cause of oedema.

History and Physical Examination

• Site, duration and laterality (unilateral / bilateral) of the oedema
• Accompanying symptoms (dyspnoea, chest pain, changes in urine)
• Medication history
• Pitting versus non-pitting distinction
• Jugular venous distension, hepatomegaly, basal crackles (signs of heart failure)

Laboratory Tests

• Full blood count: Anaemia assessment
• Serum albumin: Hypoalbuminaemia (liver disease, nephrotic syndrome, malnutrition)
• Liver function tests: AST, ALT, bilirubin, INR
• Renal function tests: Urea, creatinine, GFR
• Urinalysis: Proteinuria (nephrotic syndrome)
• BNP/NT-proBNP: A heart-failure biomarker (elevation supports heart failure)
• TSH: Screen for hypothyroidism
• D-dimer: When DVT is suspected

Imaging

• Echocardiography: Cardiac function, valve disease, ejection fraction
• Venous Doppler ultrasound: Gold standard for diagnosing DVT
• Chest X-ray: Pulmonary oedema, pleural effusion, cardiomegaly
• Abdominal ultrasound: Ascites, hepatomegaly, portal hypertension

Treatment Approaches

The foundation of oedema treatment is treating the underlying cause. Symptomatic treatment is added on top.

1. Diuretic Therapy

Diuretics increase the kidneys' excretion of sodium and water, helping the oedema to resolve.

• Loop diuretics (furosemide, bumetanide): The strongest diuretics; first-line for heart failure, kidney failure and pulmonary oedema
• Thiazide diuretics (hydrochlorothiazide): For mild oedema and hypertension
• Potassium-sparing diuretics (spironolactone): For ascites in liver cirrhosis and for heart failure

Caution: Electrolyte imbalances (hypokalaemia, hyponatraemia), dehydration and renal dysfunction can develop with diuretic use. Regular laboratory monitoring is required.

2. Salt Restriction

Reducing daily sodium intake to below 2 g (5 g of salt) is the most important dietary measure for reducing fluid retention. Processed foods, tinned goods, pickles, brined foods and fast food are high-sodium sources.

3. Fluid Restriction

In severe hyponatraemia or advanced heart failure, daily fluid intake may be limited to 1–1.5 litres.

4. Compression Therapy

In venous insufficiency and lymphoedema, compression stockings or bandages support venous return and reduce oedema. The compression class (20–30 mmHg, 30–40 mmHg) is chosen according to the severity of the condition.

5. Elevation

Raising the affected limb above heart level uses gravity to aid venous return. Elevating the legs for 15–30 minutes several times a day eases symptoms.

6. Treatment of the Underlying Cause

• Heart failure: ACE inhibitors / ARBs, beta-blockers, diuretics, aldosterone antagonists, SGLT2 inhibitors
• Nephrotic syndrome: Immunosuppressive therapy (depending on the underlying glomerulopathy), ACE inhibitors
• Liver cirrhosis: Sodium restriction, spironolactone +/- furosemide, paracentesis (for large-volume ascites)
• DVT: Anticoagulant therapy (heparin, followed by warfarin or a DOAC)
• Lymphoedema: Complete decongestive therapy (skin care, lymphatic drainage massage, compression, exercise)
• Drug-induced: Stop or switch the offending drug

When Should You See a Doctor?

• Sudden-onset unilateral leg swelling (suspected DVT)
• Oedema together with shortness of breath and cough (pulmonary oedema / heart failure)
• Morning oedema around the face and eyes (suspected kidney disease)
• Rapidly progressing generalised swelling
• Sudden increase in oedema during pregnancy (suspected pre-eclampsia)
• Oedema accompanied by fever, redness and pain (infection / cellulitis)
• Persistent, unexplained oedema

Conclusion

Oedema is an important clinical sign telling us that an imbalance exists somewhere in the body. Mild, transient oedema is usually harmless, but persistent, progressive oedema, or oedema accompanied by other symptoms, can be a sign of serious systemic disease. Correct diagnosis depends on identifying the underlying cause and planning appropriate treatment. Understanding the cause of oedema is the foundation of its treatment.

Wishing you good health.
Dr. Emre Gecer

References

• Harrison's Principles of Internal Medicine, 22nd Edition — Chapter: Edema
• Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 12th Edition
• Cho S, Atwood JE. Peripheral edema. Am J Med. 2002;113(7):580-586