Disseminated Intravascular Coagulopathy

Acquired, widespread activation of coagulation with loss of localisation. Excessive thrombin and fibrin generation consumes platelets and clotting factors, producing microvascular thrombosis, organ dysfunction, and — once the consumption outruns production — bleeding.

DIC is always secondary. It is never the primary diagnosis, and the priority is finding and treating what caused it.

Two clinical tempos

The distinction drives both the presentation and the treatment.

Slowly evolving (weeks to months)

• Mainly venous thromboembolism; bleeding is uncommon.
• Typical settings: cancer, aortic aneurysm, cavernous haemangioma.
• Mild thrombocytopenia, normal-to-minimally prolonged PT/APTT, normal or moderately low fibrinogen, raised D-dimer. Early APTT may even be short.

Rapidly evolving (hours to days)

• Mainly bleeding, plus microvascular thrombosis causing multi-organ failure.
• Severe thrombocytopenia, markedly prolonged PT/APTT, rapidly falling fibrinogen, high D-dimer.

Pathophysiology

Tissue factor is exposed to blood, activating factor VII and the extrinsic pathway → thrombin and fibrin form throughout the circulation. Cytokine-stimulated endothelium releases tissue plasminogen activator, so fibrinolysis is activated in parallel. Plasmin cleaves fibrin into D-dimers and other degradation products, which themselves bind platelets and inhibit their function — which is why DIC causes both thrombosis and bleeding. Protein C and antithrombin III pathways are dysregulated, and raised PAI-1 further disturbs the balance.

Causes

Common

• Sepsis — the most common cause; the process occurs in 30–50% of severe sepsis. Classically gram-negative, but gram-positive prevalence may be similar.
• Obstetric — placental abruption, amniotic fluid embolism, retained dead fetus, HELLP, pre-eclampsia.
• Malignancy — adenocarcinoma of pancreas, stomach, biliary tract, lung, prostate or breast; acute promyelocytic leukaemia. Up to 20% of metastatic adenocarcinoma or lymphoproliferative disease.
• Shock of any cause — ischaemic tissue injury releases tissue factor.

Less common

• Severe tissue damage — head trauma, burns, frostbite, gunshot wounds.
• Prostate surgery.
• Snake envenoming (venom enzymes activate coagulation factors directly).
• Acute haemolytic transfusion reaction from ABO incompatibility.
• Aortic aneurysm, cavernous haemangioma (Kasabach-Merritt syndrome).
• Pancreatitis, severe hepatic failure, major surgery (about 15% of DIC cases follow surgery), transplant rejection, ECMO.

Clinical features

• Persistent oozing from venepuncture and cannula sites, bruising at injection sites, significant GI bleeding.
• Bleeding from gums, vagina, rectum, or around urinary catheters.
• Purpura, petechiae, ecchymoses, cyanosis, skin necrosis and gangrene.
• End-organ effects: oliguria/haematuria (renal), dyspnoea or haemoptysis (pulmonary), altered mental state (cerebral), chest pain (coronary).

Investigations

Order together: platelet count, PT/INR, APTT, fibrinogen, D-dimer, and a blood film for schistocytes.

• Thrombocytopenia, or a falling platelet count.
• Prolonged PT and APTT.
• Low or rapidly falling fibrinogen — because fibrinogen is an acute-phase reactant, a declining level on two consecutive measurements is more useful than a single result.
• Raised D-dimer / fibrin degradation products — sensitive but not specific.
• Fragmented red cells (schistocytes) on film.

No single test makes or excludes the diagnosis. The ISTH DIC score combines platelet count, D-dimer, PT and fibrinogen; a score above 5 indicates a high likelihood of overt DIC.

Distinguishing DIC from severe liver disease: factor VIII is not made by hepatocytes, so it is normal or high in liver disease but consumed (and therefore low) in DIC. D-dimer also tends to be higher in DIC.

Differential diagnosis

• Thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome.
• Heparin-induced thrombocytopenia.
• Immune thrombocytopenia.
• Dysfibrinogenaemia.
• Dilutional coagulopathy from massive transfusion; trauma-induced coagulopathy.
• Primary fibrinolysis; post-thrombolysis.
• Venom-induced consumptive coagulopathy (VICC) from snake envenoming.

Management

Treat the cause — this is the priority. Antibiotics for sepsis, delivery or uterine evacuation for obstetric causes, surgery for trauma, volume replacement for hypotension. If the cause is controlled, DIC settles quickly.

Blood products only for active bleeding, high bleeding risk, or before a procedure — not to correct numbers alone.

• Platelets — transfuse below 50 × 10⁹/L if actively bleeding, or 10–20 × 10⁹/L if not bleeding but at high risk.
• Cryoprecipitate — for fibrinogen falling rapidly or below 1.0 g/L. Also supplies factor VIII, von Willebrand factor and factor XIII.
• Fresh frozen plasma — 15–30 mL/kg, to replace clotting factors and the natural anticoagulants antithrombin and proteins C, S and Z.
• Prothrombin complex concentrate — not recommended in DIC; it contains only some factors and carries a theoretical thrombotic risk.

Heparin

• Useful in slowly evolving DIC with venous or arterial thrombosis, and in chronic DIC from aneurysm.
• Indicated in retained dead fetus with progressive falls in platelets, fibrinogen and factors — give for several days to control the DIC, then stop and evacuate the uterus.
• Not indicated in rapidly evolving DIC with bleeding or bleeding risk.
• Patients with DIC who are not bleeding should have prophylactic heparin or LMWH.

Prognosis

Mortality roughly doubles in septic or severely injured patients who also develop DIC. Early recognition in the critically ill is what changes outcomes.