A 55-year-old woman develops unilateral leg swelling after iliofemoral deep vein thrombosis. The oedema is best explained by which change in Starling forces across the capillary wall?

• A Decreased capillary hydrostatic pressure with increased interstitial hydrostatic pressure
• B Decreased plasma colloid osmotic pressure from protein loss
• C Increased capillary hydrostatic pressure transmitted from raised venous pressure behind the obstruction ✓
• D Increased lymphatic flow removing interstitial fluid faster than it forms

Explanation

Venous obstruction raises pressure in the venules draining the limb, and since capillaries lie in series with them, capillary hydrostatic pressure climbs. Filtration across the capillary wall then exceeds the capacity of lymphatic drainage and interstitial fluid accumulates as pitting oedema. Plasma oncotic pressure is unaffected because albumin is not lost in thrombosis, unlike nephrotic syndrome. Raised lymphatic flow would be protective and cannot itself produce swelling.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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