Hematology, Oncology & Immunology · Topic 10 of 26

Disseminated Intravascular Coagulation (DIC)

Hematology · consumptive coagulopathy

Disseminated Intravascular Coagulation (DIC)

Clotting and bleeding at once from a systemic trigger: confirm the lab pattern, treat the cause, and replace products only for bleeding or procedures.

Key numbers

ISTH score ≥ 5: overt DICISTH score ≥ 5

Replace products only for bleeding or proceduresFibrinogen < 100 mg/dL

01 · Defined byLow platelets, long PT, low fibrinogen

Acute DIC lab pattern: thrombocytopenia, prolonged PT and aPTT, high D-dimer (fibrin degradation products) and a low or falling fibrinogen; the smear may show schistocytes.

02 · CalculateISTH score ≥ 5: overt DIC

The ISTH overt-DIC score (platelets, D-dimer, PT prolongation, fibrinogen) is used only when DIC is clinically suspected: 5 or more is compatible with overt DIC — rescore daily; below 5, repeat in 1–2 days.

03 · DoTreat the underlying cause first

Correcting the cause is the priority — broad-spectrum antibiotics and source control for sepsis, uterine evacuation for abruption, volume resuscitation for shock; when the trigger is controlled, DIC subsides quickly.

What it is

Core idea

Systemic clotting that consumes platelets and factors must knowDIC is excessive systemic thrombin and fibrin generation that consumes platelets and clotting factors, with secondary fibrinolysis — so it causes both microvascular thrombosis and bleeding, and it is always secondary to another disorder.

Causes & risk factors

Why it happens

Triggers: sepsis, trauma, obstetric, cancerCommon triggers: sepsis (especially gram-negative), shock, severe trauma, burns or head injury, obstetric catastrophes (abruption, amniotic fluid embolism, retained products), adenocarcinomas and acute promyelocytic leukemia, ABO-incompatible transfusion and snake venom.

Presentation

What you'll see

Acute DIC bleeds; chronic DIC clotsRapidly evolving DIC (hours to days) causes oozing from IV and puncture sites, ecchymoses and GI bleeding with organ failure; slowly evolving DIC (cancer, aneurysm) mainly causes venous thromboembolism with little bleeding.

Diagnosis & monitoring

Work-up

ISTH points: platelets, D-dimer, PT, fibrinogenISTH points: platelets 50,000–99,000 = 1, < 50,000 = 2; D-dimer moderate rise = 2, strong = 3; PT up 3–5 s = 1, ≥ 6 s = 2; fibrinogen < 100 mg/dL = 1.

Trend fibrinogen: a normal value can misleadFibrinogen is an acute-phase reactant, so an inflamed patient with DIC may still have a normal level; a falling fibrinogen on two consecutive measurements supports the diagnosis.

Do right now

In this order

First moves

Low platelets, long PT, low fibrinogen

→

ISTH score ≥ 5: overt DICISTH score ≥ 5

→

Treat the underlying cause first

→

Replace products only for bleeding or proceduresFibrinogen < 100 mg/dL

Why each step

Low platelets, long PT, low fibrinogenAcute DIC lab pattern: thrombocytopenia, prolonged PT and aPTT, high D-dimer (fibrin degradation products) and a low or falling fibrinogen; the smear may show schistocytes.

ISTH score ≥ 5: overt DICThe ISTH overt-DIC score (platelets, D-dimer, PT prolongation, fibrinogen) is used only when DIC is clinically suspected: 5 or more is compatible with overt DIC — rescore daily; below 5, repeat in 1–2 days.

Treat the underlying cause firstCorrecting the cause is the priority — broad-spectrum antibiotics and source control for sepsis, uterine evacuation for abruption, volume resuscitation for shock; when the trigger is controlled, DIC subsides quickly.

Replace products only for bleeding or proceduresGive blood products for serious or critical-site bleeding or before urgent surgery, not for numbers alone: cryoprecipitate when fibrinogen is below 100 mg/dL or falling fast, plasma for other factors, platelets for thrombocytopenia.

Management

Orders

No heparin in acute bleeding DICHeparin is generally not given in rapidly evolving DIC with bleeding; it is used for slowly evolving DIC with venous or arterial thrombosis (cancer, aneurysm) and for DIC from a retained dead fetus.

APL with DIC: tretinoin corrects itAcute promyelocytic leukemia commonly presents with DIC; in APL with t(15;17), all-trans retinoic acid (tretinoin) corrects the DIC in 2–5 days — suspect APL when DIC accompanies a new leukemia.

Red flags & don'ts

Avoid harm

Avoid prothrombin complex concentrate avoidProthrombin complex concentrate is not recommended for DIC because it may worsen thrombosis; plasma is the source of clotting factors and natural anticoagulants.

The rules

Know these

Platelets for bleeding or a count below 10,000–20,000In bleeding DIC, transfuse platelets for a rapidly falling count or a count below 10,000–20,000/mcL; nonbleeding patients do not need prophylactic platelets above 10,000/mcL.

DIC or TTP?

Commonly confused

PT and aPTT	Prolonged
Fibrinogen	Low or falling
Trigger	Sepsis, trauma, obstetric catastrophe, cancer
Treatment	Treat the cause; platelets, cryoprecipitate and plasma for bleeding

Commonly confused

Tell apart

Low factor VIII separates DIC from liver diseaseSevere liver disease can mimic DIC's labs; factor VIII is consumed (low) in DIC but normal or high in liver disease, and D-dimer tends to be higher in DIC.

More detail

Reference

Show 5 reference facts

DIC usually starts with tissue factor exposure to blood (extrinsic pathway); plasmin then generates D-dimers and fibrin degradation products, which themselves impair platelet function.

Sepsis-associated DIC has a thrombotic phenotype with suppressed fibrinolysis that drives organ failure, whereas DIC with hematologic malignancy (APL) is fibrinolytic and bleeds.

Each unit of cryoprecipitate contains about 250 mg of fibrinogen plus about 80 units each of factor VIII and von Willebrand factor, and factor XIII.

In slowly evolving DIC the aPTT may be shorter than normal, because activated clotting factors circulate.

The benefit of antithrombin concentrate in severe, rapidly evolving DIC is unresolved; restoring blood volume when the patient is hypotensive is essential to halt DIC.

Pearl

DIC is never the primary diagnosis — it is the blood's alarm that something else (sepsis, trauma, the placenta, a cancer) is out of control.

Sources · Merck Manual Professional — Disseminated Intravascular Coagulation (DIC) (Jul 2025) · MDCalc — ISTH Criteria for Disseminated Intravascular Coagulation (Taylor FB et al., ISTH SSC 2001) · Pène F, Russell L, Aubron C. Thrombocytopenia in the intensive care unit: diagnosis and management. Ann Intensive Care 2025;15:25 · Gauer RL, Whitaker DJ. Thrombocytopenia: Evaluation and Management (Table 5: DIC). Am Fam Physician 2022;106(3):288–298 · Merck Manual Professional — Acute Myeloid Leukemia (AML) (APL and DIC) · Merck Manual Professional — Blood Products (cryoprecipitate) · Metcalf RA et al. Platelet Transfusion: 2025 AABB and ICTMG International Clinical Practice Guidelines. JAMA 2025;334(7):606–617 (abstract via Europe PMC) · Merck Manual Professional — Thrombotic Thrombocytopenic Purpura (TTP) · MDCalc — PLASMIC Score for TTP (INR < 1.5 favors TTP) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).