Occlusion of the inferior vena cava produces, if life is continued, an immense dilatation of the veins of the abdomen and of the thighs. By compressing the abdominal veins it can be seen that the blood-current is reversed, flowing upward through vessels anastomosing with the intercostal and internal mammary veins. Internally, the circulation is carried on chiefly by the azygos, which may become as large as the normal cava.
There is usually, but not always,16 an extreme degree of ascites, together with anasarca of the lower half of the body. After a time, however, as the tributary circulation becomes established, the effusion will be reabsorbed.
16 Le Progrès Médical, May 26, 1877; Med. Record, July 28, 1877.
If the obstruction involves the portal vein, the ascites will be still more marked. In this case there is also enlargement of the spleen. When the cava is occluded above the point at which it receives the renal veins, congestion of the kidneys results, which in time produces interstitial change. Yet even here the establishment of the collateral circulation may be sufficiently prompt to avert the danger.
Anomalies of the cava are occasionally observed. Osler has reported a case in which the inferior cava was represented only by a fibrous cord. The condition was probably congenital.17 Greenfield mentions a case in which the descending cava was absent, both brachio-cephalic trunks passing into the heart by the coronary sinus.18
17 Journal of Anatomy and Physiology, April, 1879.
18 Med. Times and Gazette, April 22, 1876.
If the cause of the occlusion of either cava be not such as of itself to destroy life, the patient may get on with some degree of comfort for many years. The establishment of the collateral circulation sometimes keeps pace with the increasing obstruction, so that little or no ascites or oedema occurs.19
19 Turpin, "Obliteration Inf. Vena Cava," N. O. Med. and Surg. Journal, 1881, p. 575.
The TREATMENT of obstruction of either of the venæ cavæ can, as a rule, be only palliative. In the great majority of cases the cause is entirely beyond our reach. All violent muscular exertion, making an excessive demand upon the circulation, should be avoided. While the blood should not be impoverished, as that would favor dropsical effusions, the patient, on the other hand, should not be allowed to become plethoric through the influence of his enforced sedentary habits. The diet should therefore be light and digestible, and over-feeding should be carefully avoided. The occasional use of saline purgatives may be required. Dropsical accumulations may call for the administration of diuretics or drastic cathartics, and perhaps for tapping.