Occlusion of the vena portæ, by obstructing the return of the blood from the intestines, gives rise to rapid and abundant effusion into the abdominal cavity. As the gastric vein cannot empty itself, there is congestion of the stomach, often ending in hemorrhage, the blood being both vomited and passed by stool. The spleen also is enlarged by passive engorgement, its vein depending upon the portal for an outlet. This assemblage of symptoms renders the diagnosis almost positive.20 There is no enlargement of the liver unless the hepatic vein is also involved.
20 An interesting case is reported by A. A. Smith in the N.Y. Med. Journal, January, 1880.
Paget maintains that the occlusion of the principal vein of a limb may result in an increased growth of some of the tissues, especially of the muscles.
Degenerations.
Fatty degeneration is rarely observed in the veins, but it occasionally occurs in those which have long been subjected to excessive strain, which by compressing the nutrient vessels affects the nutrition of the walls.
Calcification is less rare. It results in the formation of plates or rings which closely resemble bone in their structure. Such plates may not unfrequently be felt in old superficial varicose veins. Sometimes these formations project as spines into the lumen of the vessel, and, coagula forming about them, a thrombus is the result.21
21 See preceding reference.
Cancer of the veins is rare as a primary affection, but it is not uncommon when the vessel traverses a cancerous mass. The morbid process readily penetrates the thin wall of the vessel, and cancerous nodules form on the inside and become the starting-point of thrombi which are soon permeated and supplanted by the heterologous growth. This is sometimes moulded to the shape of the vein, and fills it for some distance in the form of a cylindrical plug. Fragments may be swept away in the blood-current and give rise to secondary cancer at the point of arrest in the liver or lungs. Virchow has described a case of primary sarcoma of the inferior cava.
The existence of syphilitic lesions in the veins has not been satisfactorily demonstrated. It is positively denied by some authorities, while certain appearances found in the veins, especially of new-born children, are attributed by other writers to syphilitic inheritance.
Phlebolithes.