Disseminated Intravascular Coagulation (DIC)

Disseminated intravascular coagulation is an acquired syndrome in which systemic activation of coagulation generates fibrin clots throughout the small vessels while simultaneously consuming platelets and clotting factors, so that the patient may bleed and clot at the same time. This topic describes the pathophysiology of this consumptive coagulopathy and the laboratory pattern and scoring criteria used to recognize it.

Definition

Disseminated intravascular coagulation is an acquired, secondary syndrome of systemic intravascular activation of coagulation that consumes platelets and clotting factors and activates fibrinolysis, producing simultaneous microvascular thrombosis and a bleeding tendency.

Scope

Coverage includes the mechanisms by which an underlying trigger (such as sepsis, malignancy, trauma, or obstetric complications) drives widespread thrombin generation, the resulting laboratory abnormalities, and the consensus scoring systems used to grade overt DIC. It is a reference and diagnostic-pattern overview, not a management protocol; treatment, which centers on the underlying cause, is outside its scope. A parallel hematology entry treats DIC from the clinical-hematology perspective.

Core questions

• How does an underlying disorder trigger systemic, uncontrolled coagulation activation?
• Why can DIC cause both thrombosis and bleeding in the same patient?
• Which laboratory abnormalities and scoring criteria define overt DIC?
• How is consumptive coagulopathy distinguished from other causes of abnormal coagulation tests?

Key concepts

• Systemic tissue-factor-driven coagulation activation
• Consumption of platelets and clotting factors
• Microvascular fibrin thrombi
• Secondary fibrinolysis and fibrin degradation products
• Elevated D-dimer and prolonged PT/aPTT
• ISTH overt-DIC scoring system
• DIC as a secondary syndrome of an underlying trigger

Mechanisms

DIC begins when an underlying condition causes widespread exposure or expression of tissue factor, igniting systemic thrombin generation that is no longer confined to a site of injury. Fibrin is deposited throughout the microvasculature, which can impair organ perfusion, while the ongoing reactions consume platelets and coagulation factors faster than they are replaced. Secondary activation of fibrinolysis then breaks down fibrin, releasing fibrin degradation products and elevating D-dimer. The combined consumption and fibrinolysis explain the paradox of concurrent thrombosis and bleeding. The laboratory signature is a falling platelet count, prolonged PT and aPTT, falling fibrinogen, and rising fibrin-related markers; consensus scoring systems combine these to identify overt DIC.

Clinical relevance

Recognizing the laboratory pattern of DIC is important because it signals a serious underlying disorder and a dysregulated hemostatic state. This entry explains the syndrome and its diagnostic criteria as reference material; it does not provide treatment guidance, and care of an affected patient depends on identifying and addressing the underlying cause under specialist supervision.

Epidemiology

DIC is not a primary disease but a complication, occurring most often in the setting of severe sepsis, major trauma, certain malignancies, and obstetric emergencies; its frequency and severity therefore mirror those of the triggering conditions.

History

Once described under terms such as defibrination syndrome and consumptive coagulopathy, DIC was reconceived as a systemic dysregulation of coagulation secondary to an underlying disorder. The International Society on Thrombosis and Haemostasis subcommittee work led by Taylor and colleagues produced a scoring system for overt DIC, and subsequent British and international guidelines consolidated the diagnostic approach.

Debates

How should DIC be defined and scored?

Because DIC is a dynamic process with overlapping thrombotic and hemorrhagic features, consensus scoring systems combine platelet count, fibrin markers, prothrombin time, and fibrinogen to identify overt disease, but the optimal criteria and the recognition of non-overt DIC remain discussed.

Key figures

• Marcel Levi
• Cheng Hock Toh
• Fletcher Taylor

Seminal works

• taylor-2001-scoring
• levi-toh-2009

Frequently asked questions

Why does DIC cause both clotting and bleeding?

Systemic activation of coagulation forms clots in small vessels while consuming platelets and clotting factors and triggering fibrinolysis. The depletion of these components leaves the patient prone to bleeding even as microvascular thrombosis continues.

Is DIC a disease in its own right?

No. DIC is a secondary syndrome that arises from an underlying disorder such as sepsis, trauma, malignancy, or an obstetric complication. Its laboratory pattern signals that the underlying condition has dysregulated hemostasis.