What is the pathophysiology of phlegmasia alba dolens (PAD) and phlegmasia cerulea dolens (PCD)?

Updated: Jul 27, 2020
  • Author: Cassius Iyad Ochoa Chaar, MD, MS, FACS; Chief Editor: Vincent Lopez Rowe, MD  more...
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In PAD, the thrombosis involves only major deep venous channels of the extremity, thus sparing collateral veins. The venous drainage is decreased but still present; the lack of cyanosis differentiates this entity from PCD. In PCD, the thrombosis extends to collateral veins, resulting in severe venous congestion with massive fluid sequestration and more significant edema. Without established gangrene, these phases are reversible if proper measures are taken.

Of PCD cases, 40-60% also have capillary involvement, which results in irreversible venous gangrene that involves the skin, subcutaneous tissue, or muscle. [4] Under these conditions, the hydrostatic pressure in arterial and venous capillaries exceeds the oncotic pressure, causing fluid sequestration in the interstitium. Venous pressure may increase rapidly, as much as 16- to 17-fold within 6 hours. [5, 6]

Fluid sequestration may reach 6-10 L in the affected extremity within days. Circulatory shock, which is present in about one third of patients, and arterial insufficiency may ensue. The exact mechanism for the compromised arterial circulation is debatable but may involve shock, increased venous outflow resistance, and collapse of arterioles due to increased interstitial pressure.

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