Pathology of Chronic Congestion

Chronic Passive Congestion

• Caused by long-standing lack of blood flow, leading to chronic hypoxia
• Capillary rupture can cause small hemorrhagic foci, leading to hemosiderin-laden macrophages

Generalized Systemic Congestion

• Occurs in right ventricular failure, leading to decreased venous return and blood accumulation in the venous side
• Clinically characterized by:
  • Dilated veins (e.g., increased JVP)
  • Edema (in limbs, ascites, hepatospleenomegaly)
• Morphology:
  • Liver: chronic venous congestion causing a grossly mottled appearance (Nut meg liver)
  • Mic.: congestion of central venule, necrosis of surrounding hepatocytes, and normal or fatty changed peripheral liver cells

Pulmonary Venous Congestion

• Occurs in left ventricular failure, leading to blood accumulation in surrounding capillaries
• RBCs escape to the alveolar space and are engulfed by macrophages (heart failure cells), causing cough with blood-stained sputum

Localized Venous Congestion

• Occurs in DVT of leg, leading to edema, cold, and cyanosis

Hemorrhage

• Extravasation of blood into the extravascular space
• Can be external or internal (encased within tissue, hematoma)
• Types of hemorrhage:
  • Petechiae: minute hemorrhage in skin, mucous membranes, and serosal surfaces (1-2 mm)
  • Purpura: slightly larger hemorrhages (≥3 mm)
  • Ecchymosis: 1-2 cm subcutaneous hematoma

Causes of Hemorrhage

• Trauma: e.g., penetrating wounds to the heart and large vessels
• Abnormalities of blood vessel wall: e.g., inflammatory lesions, neoplastic invasion, and vascular diseases
• High pressure within blood vessel: e.g., systemic hypertension, varicose veins

Effects of Acute Hemorrhage

• Depend on volume and rate of blood loss
• Sudden loss of 33% of blood volume can lead to death, while gradual loss of more than 50% blood volume can be serious but not fatal

Shock

• State in which the supply of blood to the tissues is inadequate to meet metabolic demands
• Characterized by systemic hypotension due to reduced cardiac output or reduced effective circulating blood volume

Classification of Shock

• 1. Hypovolemic shock: real decrease in blood volume due to hemorrhage, fluid loss, or severe burns
• 2. Cardiogenic shock: relative decrease in blood volume due to myocardial infarction, rupture of the heart, pulmonary embolism, arrhythmias, or cardiac tamponade

Hyperemia and Congestion

• Hyperemia: active process of arteriolar dilation, leading to increased blood flow and erythema
• Congestion: passive process of impaired outflow from tissue, leading to cyanosis and edema