Varieties. — A thrombus occupying the position where coagulation began is called a primitive thrombus; when it gradually extends from this point along the vessel, an extension or produced thrombus. A laminated thrombus re sults from a process of continuous co agulation; a non-laminated, or uniform, thrombus from an intermittent coagula tion. When a thrombus adheres to some part of the vessel-wall it is called a lateral, or parietal, thrombus; when it completely fills the vessel, an obstruct ing, or obliterating, thrombus; after a thrombus is formed it may undergo cer tain changes by which spaces are left in it, giving it a spongy consistency and allowing the blood to flow through it, producing what is termed a canalized thrombus.
Finally, a thrombus may be venous, arterial, cardiac, capillary, or lymphatic according to the vessel in which throm bosis takes place, the most frequent seat of the latter being in the veins, where the circulation is naturally feeble.
Symptoms. — The symptoms of this process are those of arrested circulation.
They differ according to the vessel af fected. If a main venous trunk be ob structed and a compensatory collateral circulation cannot be rapidly established, there are produced passive hypemmia, venous dilatation, serous transudation, and occasionally hremorrhage in the vi cinity of the occluded vein, with dilata tion of the collateral channels. Moist gangrene may result in extreme cases_ According to the location of the vein af fected we may have hydrothorax, ascites, or anasarca of an extremity; hemorrhage from the stomach, intestine, or kidney; cyanosis and wdema of the face and neck, etc. The symptoms of arterial throm bosis are mainly those of arterial em bolism.
Diagnosis. — The diagnosis is usually easy if close attention to the history of the case and the symptoms be observed. Differentiation of thrombi and post-mor tem coagula may be made if the fact is borne in mind that a post-mortem coagu lum never completely fills the vessel, as after the clot has shrunken there is no further supply of blood to fill up the space between the latter and the vessel wall; post-mortem coagula are never laminated, are looser in texture and moister, do not adhere so closely to the wall of the vessel, and, though they may be either colored or colorless, they never exhibit the appearances due to the changes which normally take place in thrombi.
Etiology.—Thrombosis may be due to certain alterations in the lining mem brane of the vessels, producing an ob struction or roughening. and to retarda
tion or arrest of the circulation; the pres ence of foreign bodies and of the micro zymes of septic processes may be consid ered as having a causal relation to this process. Hyperinosis, or abnormal in crease in the fibrin factors of the blood, and diminished fluidity, as in cholera, may be regarded as predisposing causes which may become active in conjunction with a retardation of the circulation. Of all these causes, retardation of the circu lation is the most important.
The principal causes of venous throm bosis are two. The first cause is in juries of veins where Nature's method of arresting hemorrhage is the formation of thrombi. The thrombus may extend along the vein, causing blocking of ve nous trunks at a distance from the orig inal site of the injury, as is seen after par turition, where thrombosis of the uterine sinuses may extend to the iliac and fem oral veins. The second cause is inflam mation of the layers of the vein, by alter ing the condition of the lining mem brane; in many cases of phlebitis, how ever, the thrombosis is the primary lesion, the inflammation of the layers of the vein being secondary. Other causes of venous thrombosis are pressure upon the veins; dilatation; arrest of the circulation in the capillary district of the vein, from em bolism or inflammatory stasis. Finally, weakened heart-action, as in marasnms and other exhausting diseases, may cause sufficient retardation of the circulation to induce venous thrombosis; these latter are mostly met with in the veins of the lower extremity and the pelvis, less fre quently in the sinuses of the Jura mater.
.1r/erica thrombosis may be caused by wounds and injuries, by degeneration of the lining membrane of the arteries, by aneurisms (by stagnation coagulation), and any condition, as embolism, that pro duces arrest of the circulation.
Cardiac thrombosis may be caused by erlocarditis, imperfect emptying of the cavities and consequent stagnation due either to valvular stenosis or lack of tone in the heart-muscle.
Capillary thrombosis may be caused by an extension from the veins and arteries, or it may be primary.
Lymphatic thrombosis is chiefly due to alteration in the constitution of the lymph whereby it acquires the property of more ready and perfect coagulation, normal lymph being only slightly co agulable. This form is mostly observed during the puerperium, in the uterine lymphatics and their continuations to the lumbar glands, and more rarely in the thoracic duct.