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Pedal Edema - General Medicine MBBS Practical Theory

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Definition

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Pathophysiology - Starling Forces

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Classification

By Laterality

• Bilateral pedal edema - Systemic causes (heart failure, nephrotic syndrome, cirrhosis, hypothyroidism, nutritional, drugs)
• Unilateral edema - Local causes (DVT, cellulitis, venous insufficiency, lymphedema, bony/soft tissue tumor)

By Type

• Pitting edema - Leaves a pit/indentation on pressing firmly for 5 seconds; seen in cardiac, renal, hepatic, nutritional causes
• Non-pitting edema - No indentation; seen in lymphedema, myxedema (hypothyroidism), lipoedema

Grading of Pitting Edema (Clinical)

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Causes (MBBS Mnemonics)

Bilateral Pedal Edema - CHIEFS

Additional Causes

• Pregnancy - Increased venous pressure from gravid uterus + hormonal changes
• Venous insufficiency - Chronic venous hypertension, varicose veins
• Malnutrition/hypoalbuminemia - Kwashiorkor, protein-losing enteropathy
• Immobility - Prolonged sitting (airplane travel), dependent position
• Heat edema - Benign, seen in elderly in hot environments; resolves with cooling

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History Taking (Key Points)

• Dyspnea, orthopnea, PND → Heart failure
• Oliguria, frothy urine, facial puffiness in morning → Nephrotic syndrome
• Jaundice, abdominal distension, alcohol history → Cirrhosis
• Weight gain, cold intolerance, constipation → Hypothyroidism
• Calf pain, redness, recent immobilization/surgery/travel → DVT
• Diurnal variation - Cardiac/venous edema increases by end of day (dependent); nephrotic edema starts periorbital in morning

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Clinical Examination

General Survey

• Pallor (anemia in CKD, liver disease)
• Icterus (liver disease)
• Facial puffiness (nephrotic syndrome - periorbital edema worst in morning)
• JVP elevation (heart failure, cardiac tamponade)
• Cyanosis
• Nutritional status - cachexia or obesity

Examination of Edema

1. Site - Dorsum of feet, ankles, pretibial region, sacrum (if bedridden), genitals (severe)
2. Extent - Feet only / up to knee / up to thigh / anasarca
3. Pitting - Press firmly over bony area (pretibial, dorsum of foot) for 5 seconds; note depth and rebound
4. Temperature - Warm = inflammation/cellulitis; cool = reduced perfusion
5. Skin changes - Pigmentation, lipodermatosclerosis, ulceration (chronic venous insufficiency); skin thickening/roughness (lymphedema); dry coarse skin (hypothyroidism)
6. Tenderness - Tender = DVT, cellulitis, inflammatory; non-tender = cardiac/renal/hepatic
7. Varicosities - Dilated superficial veins suggest chronic venous insufficiency

Systemic Examination Clues

Exam Tip: Nephrotic edema is characteristically periorbital in the morning and pedal by evening; cardiac edema is absent in the morning and worst in the evening (gravity-dependent). - Comprehensive Clinical Nephrology, 7th Ed.

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Investigations

First-Line (Must Order)

Second-Line (As indicated)

• Doppler ultrasound of lower limbs - DVT
• Venous duplex - Chronic venous insufficiency
• D-dimer - DVT screening (high sensitivity, low specificity)
• BNP / NT-proBNP - Differentiates cardiac from non-cardiac edema
• Renal biopsy - If nephrotic syndrome confirmed (identifies: minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, diabetic nephropathy, amyloidosis)
• Liver biopsy / fibroscan - Severity of cirrhosis

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Differential Diagnosis at a Glance

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Management

General Measures

• Leg elevation above the level of the heart when resting - reduces hydrostatic pressure
• Sodium restriction (<2 g/day) in cardiac and renal edema
• Fluid restriction in severe hyponatremia
• Compression stockings (graduated, 20-30 mmHg) in venous insufficiency
• Avoid prolonged standing/sitting
• Treat underlying cause (cornerstone of management)

Pharmacological Treatment

1. Heart Failure Edema

• Loop diuretics (furosemide) - First choice; inhibit Na-K-2Cl cotransporter in thick ascending limb; cause brisk natriuresis and reduction of pulmonary congestion - Katzung's Basic and Clinical Pharmacology
• Add aldosterone antagonist (spironolactone) for mortality benefit in HFrEF
• Combination loop + thiazide (metolazone) for diuretic-resistant edema; requires close K+ monitoring
• Caution: Excessive diuresis lowers filling pressures below 15 mmHg → reduces cardiac output (especially critical in right ventricular failure) - Katzung's

2. Nephrotic Syndrome Edema

• Loop diuretics - but may be less effective due to protein binding in tubules
• Salt restriction
• Treat primary cause (steroids for minimal change disease, immunosuppressants for others)
• ACE inhibitors/ARBs to reduce proteinuria

3. Cirrhosis with Ascites/Edema

• Spironolactone (first choice) - targets secondary hyperaldosteronism
• Add furosemide for synergistic effect (ratio 100 mg spironolactone : 40 mg furosemide)
• Paracentesis for tense ascites
• Salt restriction

4. Hypothyroid Edema

• Thyroid replacement (levothyroxine) - edema resolves with correction of hypothyroidism

5. Drug-Induced Edema

• Withdraw offending drug (e.g., switch amlodipine to another antihypertensive)

6. DVT

• Anticoagulation (LMWH/DOACs) - mainstay
• Compression, elevation

7. Lymphedema

• Complex decongestive physiotherapy
• Compression bandaging
• Diuretics NOT useful for pure lymphedema

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Key Diuretic Points (Pharmacology - Viva Favorite)

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High-Yield Exam Points (Viva/Short Notes)

1. Most common cause of bilateral pedal edema in India: Congestive heart failure
2. Edema that does not change with dependency: Protein-loss edema (hypoalbuminemia) - because it's oncotic, not hydrostatic
3. Edema worse in morning (face/periorbital): Nephrotic syndrome
4. Non-pitting edema causes: Lymphedema, myxedema (hypothyroidism), lipoedema, pretibial myxedema (Graves' disease - pretibial only)
5. Unilateral edema: Always think DVT or local lymphatic/venous obstruction
6. Diuretics contraindicated in: Pure chronic venous insufficiency edema - do NOT use diuretics as sole therapy
7. Heat edema: Benign; in elderly in hot climates; history + examination exclude systemic cause
8. Anasarca = generalized edema involving face, abdomen (ascites), pleural effusions + limbs; severe nephrotic syndrome, end-stage liver failure
9. Starling's law application: Edema forms when capillary hydrostatic pressure > oncotic pressure, i.e., net filtration exceeds lymphatic drainage capacity
10. BNP/NT-proBNP: Most useful single test to differentiate cardiac from non-cardiac pedal edema

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Practical Viva Approach

1. Confirm it is edema (pitting test)
2. Bilateral vs. unilateral (systemic vs. local cause)
3. Take history - duration, diurnal variation, associated SOB/orthopnea, frothy urine, jaundice, drug history
4. Examine - JVP, S3, crepitations (cardiac); periorbital puffiness, ascites (nephrotic/hepatic); thyroid enlargement, delayed reflexes (hypothyroid); calf tenderness (DVT)
5. Investigate - Serum albumin, urine protein, RFT, LFT, ECG, echo, TSH
6. Treat underlying cause + diuretics as appropriate

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