OBSERVATIONS ON THE HEPATIC VENOUS CIRCULATION WITH SPECIAL REFERENCE TO THE SPHINCTERIC MECHANISM

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Abstract
The existence of a sphincteric or "throttle" mechanism in the liver of the dog has long been known. Largely on a histologic anatomic basis it was considered unique to dogs. Two principal ideas as to its exact location have been put forward. Mautner and Pick localized it in the smaller hepatic veins. Bauer and his associates presented evidence that it was a muscle ring at the entrance of the hepatic veins into the vena cava. This was based on a physiologic and anatomic conception. This latter view has gained most acceptance. In the present studies evidence was accumulated that there was not a marked constriction in that part of the hepatic vein by passing a polythene catheter up to 9 cm. within the liver, well beyond any single sphincter, and finding pressure readings typical of the systemic venous pressure rather than the portal venous pressure following injns. of appropriate drugs. This study has shown that the mechanism is, in fact, a diffuse spasm of the entire hepatic venous side of the vasculature of the liver. This is even more pronounced in the smaller vessels than in the larger ones. This spasm may be induced in dogs by extracts of Ascaris suum, hydatid cyst fluid, anaphylactic shock, histamine, digitoxin and probably by protamine. It has also been observed after the hepatic artery had been occluded for 2 hrs. These constriction rings were absent or were extremely slight in the livers of several control dogs. The hepatic venous spasm has been produced in some but not all cats, and in white rats, but insufficient data were obtained to draw final conclusions in this regard in spp. other than the dog. Accurate localization of this mechanism should open new areas for investigation. Observers in the past have looked for a different type of mechanism. There is some evidence in this study that other animals show the phenomenon. There is slight suggestive evidence that this mechanism may be present in man. This follows: (1) the well-known shock caused by spillage of hydatid cyst fluid into the peritoneal cavity, which may be caused by a spasm of the hepatic venous system; (2) certain cases of Chiari''s syndrome in which a closure of hepatic veins is discovered at necropsy; (3) the much-disputed reduction in circulating blood volume on digitalization of a patient, which may be owing to an increased resistance of the hepatic veins resulting in storage of blood in the liver.