Disseminated Intravascular Coagulation (DIC)

How DIC happens

Normally, clotting is switched on only at the site of an injury and is kept in check by natural anticoagulants and the clot-dissolving (fibrinolytic) system. In DIC, a trigger releases large amounts of tissue factor or damages the lining of blood vessels everywhere. Clotting then starts in the circulation as a whole.

This has two effects:

1. Clotting: small clots of fibrin and platelets block tiny blood vessels in the kidneys, lungs, brain, liver and skin, starving them of oxygen and causing organ failure.
2. Bleeding: platelets and clotting factors are consumed faster than the body can make them. The fibrinolytic system also breaks clots down, releasing fibrin degradation products (measured as D-dimer) that further impair clotting.

That is why DIC is called a consumptive coagulopathy: the body runs out of what it needs to clot. For other causes of abnormal clotting, see coagulopathy.

What causes DIC

DIC never occurs by itself. The common triggers are:

• Sepsis: the most common cause, especially with gram-negative bacteria and meningococcal infection.
• Major trauma and burns: particularly with head injury, crush injuries and large blood loss.
• Cancer: acute promyelocytic leukemia, a type of acute myeloid leukemia, often causes severe bleeding DIC; solid tumors of the pancreas, prostate, lung and stomach tend to cause slower, chronic DIC.
• Pregnancy complications: placental abruption, amniotic fluid embolism, severe preeclampsia and HELLP syndrome, retained dead fetus and severe postpartum bleeding.
• Other: severe acute pancreatitis, liver failure, heatstroke, some snake bites, transfusion reactions and large vascular malformations or aneurysms.

Symptoms

Symptoms are a mix of the triggering illness and the clotting problem.

Bleeding signs (more common in acute DIC)

• Oozing from IV lines, wounds, surgical sites and gums
• Nosebleeds, blood in the urine or stool, vomiting blood
• Widespread bruising and tiny pinpoint spots (petechiae)
• Heavy bleeding after childbirth

Clotting signs (more common in chronic DIC)

• Deep vein thrombosis or pulmonary embolism
• Cold, mottled or darkening fingers and toes; patches of dying skin (purpura fulminans in severe infection)
• Organ dysfunction: confusion, low urine output, breathing difficulty, jaundice

Acute vs chronic DIC

How DIC is diagnosed

There is no single test. Doctors combine the clinical picture with repeated blood tests:

• Platelet count: low or falling quickly
• Prothrombin time (PT) and aPTT: prolonged
• Fibrinogen: low (may look normal early, because fibrinogen rises in inflammation and pregnancy)
• D-dimer or fibrin degradation products: markedly raised
• Blood smear: fragmented red blood cells (schistocytes) in some cases

The ISTH DIC score gives points for platelet count, D-dimer, PT and fibrinogen; a score of 5 or more supports overt DIC. Trends over hours are more informative than one result. Doctors also distinguish DIC from look-alikes such as thrombotic thrombocytopenic purpura, heparin-induced thrombocytopenia and liver failure, which are treated differently.

Treatment

Treat the underlying cause

This is the most important step. It may mean antibiotics and source control for sepsis, delivering the baby and placenta in an obstetric emergency, surgery and resuscitation after trauma, or starting specific treatment (such as all-trans retinoic acid) for acute promyelocytic leukemia.

Blood product support

Given mainly for active bleeding or before procedures, not to correct numbers alone:

• Platelet transfusion: when platelets are very low and bleeding, or high bleeding risk
• Fresh frozen plasma: replaces clotting factors when PT is prolonged and bleeding
• Cryoprecipitate or fibrinogen concentrate: when fibrinogen is low
• Red cell transfusion: for blood loss

Anticoagulation

When clotting dominates, for example DIC with deep vein thrombosis in cancer, carefully dosed heparin may be used. This is decided by a hematologist, balancing clot and bleeding risk.

Organ support

Patients with acute DIC are usually treated in intensive care, where they may need fluids, blood pressure support, oxygen or ventilation, and dialysis.

Outlook

Acute DIC carries a high risk of death, mainly from the underlying illness and multi-organ failure. In sepsis and trauma, developing DIC roughly doubles the risk of dying compared with similar patients without it. When the cause is quickly reversible, as in placental abruption after delivery, clotting tests often normalize within a day or two. Chronic DIC in cancer can be controlled for long periods with anticoagulation and cancer treatment.

Frequently asked questions

What is DIC in simple terms?

DIC is a condition in which the body's clotting system goes into overdrive everywhere at once. It forms many tiny clots that block blood flow to organs, then runs out of platelets and clotting factors, so the person also bleeds. It is always caused by another serious illness.

What are the most common causes of DIC?

Sepsis is the most common cause. Others include major trauma, burns, certain cancers (especially acute promyelocytic leukemia), pregnancy emergencies such as placental abruption and amniotic fluid embolism, and severe pancreatitis.

What blood tests show DIC?

Typical findings are a low or falling platelet count, a prolonged prothrombin time, low fibrinogen and a markedly raised D-dimer. Doctors often combine these into the ISTH score. Repeating the tests every few hours shows whether DIC is worsening or improving.

Can you survive DIC?

Yes. Many people recover, especially when the trigger can be treated quickly, such as delivering the placenta in abruption or controlling an infection. The outlook is worse when DIC accompanies severe sepsis or trauma with multi-organ failure.

Is DIC a bleeding or a clotting disorder?

Both. DIC starts with excessive clotting inside blood vessels. That clotting consumes platelets and clotting factors, which then leads to bleeding. Acute DIC usually shows mainly as bleeding, while chronic DIC more often shows as blood clots.