Introduction
- Disseminated Intravascular Coagulation is a serious acquired disorder characterized by widespread activation of the coagulation system, resulting in excessive formation of microthrombi within blood vessels.
- Continuous activation of coagulation pathways causes consumption of platelets and clotting factors, leading to simultaneous thrombosis and bleeding.
DIC is not a primary disease but occurs secondary to various clinical conditions such as:
- Sepsis
- Trauma
- Malignancy
- Obstetric complications
- Severe infections
- Massive tissue injury
Early laboratory diagnosis is essential because DIC can rapidly progress and become life-threatening.
Pathophysiology of DIC
Step 1: Initiation of Coagulation Cascade
DIC begins when large amounts of procoagulant substances enter the circulation.
Common triggers:
- Sepsis
- Trauma
- Obstetric complications
- Malignancy
- Severe tissue injury
These conditions stimulate release of:
- Tissue factor (TF)
- Cytokines (TNF-α, IL-1, IL-6)
- Procoagulant substances
Effect
- Excessive activation of coagulation pathways
Step 2: Excessive Thrombin Generation
Functions of thrombin:
- Converts fibrinogen into fibrin
- Activates platelets
- Amplifies coagulation process
Result
- Formation of widespread fibrin clots
Step 3: Formation of Microvascular Thrombi
Large amounts of fibrin are deposited within small blood vessels.
Effects
- Formation of microthrombi in capillaries and arterioles
- Obstruction of blood flow
- Reduced tissue perfusion
Organs commonly affected:
- Kidneys
- Lungs
- Liver
- Brain
- Heart
Step 4: Consumption of Platelets and Coagulation Factors
Continuous clot formation consumes:
- Platelets
- Fibrinogen
- Prothrombin
- Factor V
- Factor VIII
- Other clotting factors
Result
- Progressive depletion of coagulation components
This phenomenon is called:
Consumption Coagulopathy
Step 5: Secondary Activation of Fibrinolysis
The body attempts to remove excessive fibrin deposition by activating fibrinolytic pathways.
Mechanism
Plasminogen is converted into plasmin.
Plasmin causes:
- Breakdown of fibrin clots
- Production of fibrin degradation products (FDPs)
- Increased D-dimer formation
Result
- Increased bleeding tendency
Step 6: Development of Bleeding
Because platelets and clotting factors become depleted:
Clinical manifestations include:
- Petechiae
- Ecchymosis
- Mucosal bleeding
- Hematuria
- Gastrointestinal bleeding
- Excessive surgical wound bleeding
Step 7: Organ Dysfunction and Failure
Microvascular thrombosis reduces blood flow to organs causing:
Organ complications
Kidneys
- Acute kidney injury
Lungs
- Respiratory distress
Brain
- Neurological dysfunction
Liver
- Hepatic dysfunction
Heart
- Myocardial ischemia
Severe DIC may progress to:
- Multiple organ failure
- Shock
- Death
Causes of DIC
The causes of DIC can be classified as follows:
1. Infectious Causes
Infections, particularly severe bacterial infections, are among the most common causes of DIC.
Examples
- Septicemia (especially Gram-negative sepsis)
- Severe bacterial infections
- Viral infections
- Fungal infections
- Meningococcemia
- Malaria
Mechanism
Microorganisms release toxins and inflammatory cytokines that stimulate tissue factor release and activate coagulation pathways.
2. Obstetric Causes
Obstetric complications commonly trigger DIC due to release of tissue thromboplastin into circulation.
Examples
- Placental abruption
- Amniotic fluid embolism
- Retained dead fetus syndrome
- Severe pre-eclampsia/eclampsia
- Septic abortion
- Postpartum hemorrhage
3. Malignancies
Certain cancers may activate coagulation mechanisms.
Examples
- Acute promyelocytic leukemia (APL)
- Metastatic adenocarcinoma
- Pancreatic carcinoma
- Prostate carcinoma
Mechanism
Tumor cells may produce procoagulant substances.
4. Trauma and Tissue Injury
Severe tissue damage releases tissue factors that activate coagulation.
Examples
- Major trauma
- Extensive burns
- Head injury
- Crush injuries
- Major surgery
5. Hemolytic and Transfusion Reactions
Examples
- Acute hemolytic transfusion reaction
- Massive incompatible blood transfusion
Mechanism
Hemolysis releases procoagulant substances into circulation.
6. Vascular Disorders
Conditions affecting blood vessels may predispose to DIC.
Examples
- Giant hemangioma (Kasabach-Merritt syndrome)
- Aortic aneurysm
- Vasculitis
7. Toxic and Miscellaneous Causes
Examples
- Snake bite
- Heat stroke
- Acute pancreatitis
- Shock
- Severe liver disease
Laboratory Investigations
Laboratory investigations are essential in the diagnosis of Disseminated Intravascular Coagulation because no single laboratory test confirms the disease. DIC diagnosis is based on a combination of abnormalities showing increased coagulation, platelet consumption, and enhanced fibrinolysis.
These investigations help in:
- Early diagnosis
- Assessment of severity
- Monitoring progression
- Evaluating treatment response
1. Complete Blood Count (CBC)
CBC is usually the initial test performed in suspected DIC patients.
Findings
- Thrombocytopenia (decreased platelet count)
- Reduced hemoglobin level due to bleeding or hemolysis
- Mild leukocytosis may occur in infections
Significance
Platelets are continuously consumed during widespread clot formation, resulting in thrombocytopenia and increased bleeding tendency.
2. Platelet Count
Finding
- Platelet count markedly decreased
Mechanism
Continuous intravascular clot formation consumes large numbers of circulating platelets.
Clinical Significance
- Low platelet count indicates active consumption
- Serial measurements help monitor progression
3. Peripheral Blood Smear Examination
Peripheral smear provides evidence of red blood cell damage.
Findings
- Schistocytes (fragmented RBCs)
- Helmet cells
- Burr cells
- Fragmented erythrocytes
Mechanism
Red blood cells passing through fibrin strands within vessels become mechanically damaged.
Clinical Significance
Presence of schistocytes indicates:
- Microangiopathic hemolytic anemia
- Active intravascular coagulation
4. Prothrombin Time (PT)
Factors assessed
- Factor I (Fibrinogen)
- Factor II (Prothrombin)
- Factor V
- Factor VII
- Factor X
Findings
- PT prolonged
Mechanism
Consumption of clotting factors due to ongoing coagulation activation.
Clinical Significance
- Indicates coagulation factor depletion
- Increased risk of bleeding
5. Activated Partial Thromboplastin Time (aPTT)
aPTT assesses intrinsic and common pathways.
Factors assessed
- Factor VIII
- Factor IX
- Factor XI
- Factor XII
Finding
- aPTT prolonged
Mechanism
Consumption of intrinsic coagulation factors.
Clinical Significance
- Helps evaluate severity of coagulation abnormalities
6. Thrombin Time (TT)
Thrombin time measures conversion of fibrinogen into fibrin.
Findings
- Prolonged thrombin time
Mechanism
- Reduced fibrinogen concentration
- Interference by fibrin degradation products
Clinical Significance
Indicates impaired fibrin formation.
7. Plasma Fibrinogen Level
Finding
- Reduced plasma fibrinogen level
Mechanism
Large amounts of fibrinogen are consumed for clot formation.
Clinical Significance
- Indicates severe DIC
- Associated with increased bleeding risk
8. D-Dimer Test
Finding
- Markedly elevated D-dimer level
Mechanism
Excessive clot formation followed by fibrinolysis.
Clinical Significance
- Highly sensitive indicator of DIC
- Suggests active clot formation and breakdown
9. Fibrin Degradation Products (FDPs)
FDPs are produced during degradation of fibrin and fibrinogen.
Findings
- Increased FDP level
Mechanism
Enhanced fibrinolysis results in excessive fibrin breakdown.
Clinical Significance
- Supports diagnosis of DIC
- Indicates increased fibrinolytic activity
10. Coagulation Factor Assays
Specific clotting factors may be measured.
Findings
Reduced levels of:
- Factor V
- Factor VIII
- Factor XIII
Clinical Significance
Confirms consumption of coagulation proteins.
11. Antithrombin III Assay
Antithrombin III is a natural anticoagulant protein.
Finding
- Reduced antithrombin III level
Mechanism
Consumption occurs during excessive coagulation activation.
Clinical Significance
- Low levels indicate severe DIC
- Associated with poor prognosis
12. ISTH DIC Scoring System
The International Society on Thrombosis and Haemostasis (ISTH) developed a scoring system for DIC.
Parameters included:
- Platelet count
- PT prolongation
- Fibrinogen level
- D-dimer/FDP levels
Significance
Helps:
- Confirm diagnosis
- Assess severity
- Monitor treatment response