Blood flow through the splanchnic bed has long been considered a major component of the total circulation by virtue of its function as a blood depot,1,2 and thus, under control of the nervous system, plays a significant role as a determinant of cardiac output.3 Alterations in hepatic blood flow may cause or reflect physiological changes in the systemic circulation. It has been shown4 that after total occlusion of the thoracic aorta hepatic blood flow persisted at a level 27% of the control flow rate. This finding suggested the presence of collateral arterial circulation. Indeed, a subsequent study5 confirmed anatomically the presence of arterial anastomoses which connected the thoracic and abdominal aortas, and which became functional within a few seconds after the obstruction of the major channel.
The development of collateral venous circulation has been demonstrated by complete occlusion of inferior vena cava in man6 and
HORVATH SM, BENDER AD. Complete Occlusion of the Abdominal Vena Cava in the DogStudies of the Splanchnic, Hemodynamic, and Metabolic Responses to Vena Caval Occlusion. Arch Surg. 1961;82(5):668-673. doi:10.1001/archsurg.1961.01300110030005