DIC

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Disseminated Intravascular Coagulation (DIC)

Disseminated Intravascular Coagulation (DIC) is an acquired, life-threatening clinicopathologic syndrome characterized by widespread, systemic activation of the coagulation cascade. It is always secondary to an underlying systemic disease process. This unchecked activation results in simultaneous widespread microvascular thrombosis (leading to tissue ischemia) and catastrophic consumptive hemorrhage due to the rapid exhaustion of platelets and clotting factors.

1. Pathophysiology and Clinical Drivers

The core mechanism involves massive exposure of Tissue Factor (Factor III) or other procoagulants to circulating blood, shifting the homeostatic balance entirely toward coagulation:

Pathophysiology diagram showing procoagulant release leading to thrombi formation, factor consumption, microangiopathic hemolytic anemia, plasmin generation, and subsequent bleeding

The dual nature of DIC: microvascular fibrin deposition drives tissue ischemia and shears red blood cells, while secondary fibrinolysis produces antiplatelet FDPs that worsen active hemorrhage.
  • Sepsis and Endotoxemia: The most common trigger. Bacterial endotoxins (LPS) stimulate macrophages to release pro-inflammatory cytokines (TNF-alpha, IL-1), which upregulate tissue factor expression on endothelial cells and monocytes.
  • Obstetric Complications: Amniotic fluid contains rich concentrations of tissue factor. Abruptio placentae, amniotic fluid embolism, or retained dead fetus can breach the maternal circulation, sparking sudden, severe DIC.
  • Malignancies: Adenocarcinomas (mucin-secreting) and Acute Promyelocytic Leukemia (APL, M3 AML variant) release pre-formed procoagulants or tissue factor analogs directly from cellular granules.
  • Massive Tissue Trauma: Severe burns, extensive crush injuries, or major neurotrauma release large reservoirs of endothelial and subendothelial procoagulants into systemic circulation.

2. Clinical Manifestations

Patients presentation reflects the volatile balance between microthrombi formation and profound element depletion:

Clinical Feature Underlying Mechanism and Presentation Signs
Diffuse Hemorrhage Continuous oozing or active bleeding from intravenous catheter lines, venipuncture sites, surgical wounds, and mucosal surfaces (epistaxis, hematuria, GI bleeding). Driven by the total consumption of active platelets and factors.
End-Organ Ischemia Microvascular occlusion cuts off perfusion to vital networks. Can present as acute kidney injury (oliguria/anuria), altered mental status, or focal strokes, and patchy cutaneous gangrene (purpura fulminans).
Microangiopathic Hemolytic Anemia As red blood cells travel through narrow, fibrin-choked capillaries, they are physically sliced apart by the rigid fibrin strands, causing intravascular hemolysis.

3. Definitive Laboratory Profile

DIC is a consumptive coagulopathy that affects both primary and secondary hemostatic panels, alongside evidence of reactive fibrinolysis:

  • Platelet Count: Significantly decreased due to active incorporation into systemic microthrombi.
  • PT / INR and aPTT: Markedly prolonged because the rapid creation of systemic clots completely depletes the plasma reservoir of both intrinsic and extrinsic clotting factors.
  • Serum Fibrinogen (Factor I): Severely decreased. Fibrinogen is actively consumed and converted into fibrin clots throughout the vascular tree.
  • D-Dimer and FDPs: Markedly elevated. Widespread clotting triggers massive secondary activation of plasmin. Plasmin cleaves cross-linked fibrin clots, releasing specific D-dimer fragments into circulation.
High power light micrograph of a peripheral blood smear showing fragment red blood cells or schistocytes indicated by arrows

Peripheral blood smear demonstrating prominent, helmet-shaped schistocytes (indicated by arrows), confirming microangiopathic hemolytic anemia.