Page 135 - Textbook of Pathology, 6th Edition

119

CHAPTER 5

Figure 5.23 Fate of thrombus.

cells. The thrombus in this way is excluded from the vascular EMBOLISM
lumen and becomes part of vessel wall. The new vascular
channels in it may be able to re-establish the blood flow, Definition and Types
called recanalisation. The fibrosed thrombus may undergo Embolism is the process of partial or complete obstruction of
hyalinisation and calcification e.g. phleboliths in the pelvic some part of the cardiovascular system by any mass carried
veins. in the circulation; the transported intravascular mass Derangements of Homeostasis and Haemodynamics
3. PROPAGATION. The thrombus may enlarge in size due detached from its site of origin is called an embolus. Most
to more and more deposition from the constituents of flowing usual forms of emboli (90%) are thromboemboli i.e.
blood. In this way, it may ultimately cause obstruction of originating from thrombi or their parts detached from the
some important vessel. vessel wall.
Emboli may be of various types:
4. THROMBOEMBOLISM. The thrombi in early stage and
infected thrombi are quite friable and may get detached from A. Depending upon the matter in the emboli:
the vessel wall. These are released in part or completely in i) Solid e.g. detached thrombi (thromboemboli), athero-
bloodstream as emboli which produce ill-effects at the site matous material, tumour cell clumps, tissue fragments,
of their lodgement (page 120).
parasites, bacterial clumps, foreign bodies.
ii) Liquid e.g. fat globules, amniotic fluid, bone marrow.
Clinical Effects
iii) Gaseous e.g. air, other gases.
These depend upon the site of thrombi, rapidity of formation,
and nature of thrombi. B. Depending upon whether infected or not:
1. Cardiac thrombi. Large thrombi in the heart may cause i) Bland, when sterile.
sudden death by mechanical obstruction of blood flow or ii) Septic, when infected.
through thromboembolism to vital organs. C. Depending upon the source of the emboli:
2. Arterial thrombi. These cause ischaemic necrosis of the i) Cardiac emboli from left side of the heart e.g. emboli
deprived part (infarct) which may lead to gangrene. Sudden originating from atrium and atrial appendages, infarct in the
death may occur following thrombosis of coronary artery. left ventricle, vegetations of endocarditis.
3. Venous thrombi (Phlebothrombosis). These may cause ii) Arterial emboli e.g. in systemic arteries in the brain, spleen,
following effects: kidney, intestine.
i) Thromboembolism iii) Venous emboli e.g. in pulmonary arteries.
ii) Oedema of area drained
iii) Poor wound healing iv) Lymphatic emboli can also occur.
iv) Skin ulcer D. Depending upon the flow of blood, two special types
v) Painful thrombosed veins (thrombophlebitis) of emboli are mentioned:
vi) Painful white leg (phlegmasia alba dolens) due to i) Paradoxical embolus. An embolus which is carried from
ileofemoral venous thrombosis in postpartum cases the venous side of circulation to the arterial side or vice versa
vii) Thrombophlebitis migrans in cancer.
is called paradoxical or crossed embolus e.g. through
4. Capillary thrombi. Microthrombi in microcirculation arteriovenous communication such as in patent foramen
may give rise to disseminated intravascular coagulation ovale, septal defect of the heart, and arteriovenous shunts in
(DIC). the lungs.