ABSTRACT
The interstitium forms the junction between the microcirculation and the tissues. It is an underappreciated component contributing to regulation of metabolism, regional blood flow, and overall fluid balance. Subcutaneous edema is an abnormal increase in the amount of interstitial fluid within the superficial tissues. In dogs and cats, subcutaneous edema typically is associated with regional lymphatic or venous obstruction, profound hypoalbuminemia, vasculitis, or localized tissue injury. Subcutaneous edema caused by high capillary hydrostatic pressure in these two species is more likely to occur from localized venous obstruction or compression, rather than heart failure. Cranial vena caval compression caused by a cranial mediastinal mass or cranial caval thrombosis can lead to the cranial caval syndrome. Pleural effusion also is anticipated and the fluid might be chylous, depending on the location of the obstruction. Cranial mediastinal lymphoma and thymoma are the most common neoplastic causes of cranial caval syndrome.
