J.Jpn. Surg. Soc.. 57(6): 974-986, 1956
宿題報告
PATHOGENESIS AND PATHOLOGY OF PORTAL HYPERTENSION
|
Tomoda Surgical Department, Kyushu University Medical School Masanobu TOMODA |
Portal hypertension dose not designate an independent dusease entity admitting of any clear-cut pathological concept ; the term denotes an aggregate of manifold clinical disorders, comprising dynamic abnormality of the portal circulation and other conditions presenting clinical pictures accruing from the circulatory disturbance and yet different from each other in nature. The factors causing portal obsthruction are some of them organic and some functional ; it is essential that they should be classified into two main group-those which are clearly definable and the reatment of which cures or arrests the functional dislurbance of the liver and those, arising from an unkown cause and rather progressive in nature, not much amenable to any treatment. The two groups, the former including splenopathic toxicosis*, schistosomiasis japonica, etc. and the latter including liver cirrhosis of certain sorts, etc., take different courses and are to be treated in different ways.
The causative factors in the development of portal hypertension are manifold ; they are generally classified into two kinds, intrahepatic and extrahepatic, acording to the area where the organic portal obsstruction is occurring. Such a classification suits the purpose of clinical convenience, but the original diseases giving rise to portal hypertension should be classified into pathologically well-defined particular disease, because the prognosis and treatment of portal hypertension depend on the characteristic natures of those original diseases.
The pathology of portal obstruction is now known as a whole and needs no further explanation here. The present report is a description of the cause and development of portal hypertension, more particularly those associated diseases which are high in incidence in Japan and have not yet been paid due attention to, form our own viewpoint based on a 14 years' study of the portal system and of the spleen in the Tomoda Surgical Clinic.
2. So-called Banti's syndrom
The parlicular diseases to be taken up for discussion today are Laennec's liver-cirrhosis, splenopathic toxicosis (Tomoda, 1946), so-called congestive splenomegaly (primary, Ravenna, 1940; secondary, Rousselot, 1936), and Banti's disease (first described by Banti).
The pathologic changes produced in the liver in splenopathic toxicosis are divisible into hepatosis, cirrhosis of Kitani type** and transitional type, all derived from chronic degeneration due to splenotoxin. A cirrhotic change in the liver is naturally followed by a rise in the portol pressure, but a swollen spleen is another non-negligible faclor in bringing about this pressure rise, as to be presumed from the persistent congestion of the central splenic artery and the conspicuous drop in the portal pressure following splenectomy. In animals cutting of the splenic branch of the abdominal sympathelic nerve is followed by the production of some toxin similar in action to splenotoxin formed in splenopathic toxicosis. In such animals the liver and spleen undergo some pathologic changes as in splenopathic toxicosis, hepatic vein catheterization showing that the eslimated hepatic blood flow (EHBF) in on the decline and experimental perfusion of the liver revealing that the influence of the hepatic arterial pressure on the portal pressure is above normal. These are circumstances suggestive of the presence of some functional circulatory disturbance of the liver in this disease. We have not yet come across any case of extrahepatic block, particularly thrombosis produced in this disease, but the development of a thrombus during the course of the disease is not inconceivable, and in case it is present there will be a secondary rise in the portal pressure. A rise in the portal pressure in such a case is of secondary nature after all and dose not mean that splenotoxin is produced afyer the occurrence of portal hypertension, because splenoloxin is utterly undemonslrable in Laennec's crirhosis, schistosomiasis japonica or experimental portal hypertension, and demonstrable in the absence of portal hypertension.
It was remarkable that splenectomy had a favorable result lasting for 10 to 20 years in 144 cases of splenopathic toxicosis and of so-called Banti's disease in the Goto Surgical Clinic (the disease clinically presumed from its microscopical picture to be closely related to splenopathic toxicosis) and that death from hemorrhage of esophageal varices occurred after splenectomy in no more than 4.2% of those cases. These rcsults are suggestive of the difference between splenopathic toxicosis and so-called Banti's disease occurring in some European and American countries.
Splenomealy resulting from mechanical obstruction in the portal area and known as congestive splenomegaly is clearly distinguishable from splcnopathic toxicosis in that, in the former, there is no congestion of the central splenic artery, the splenic sinuses are enlarged and no splenotoxin is detectable. lt is to be noted besides that the literature records certain cases of portal hypertension in which no obstructive mechanism was recognizable in the portal area.
3. Splenic inhibition of bone marrow activity and hematologic changes
As is generally known, splenomegaly is often accompanied by a change in the blood due to splenic inhibition of the activity of bone marrow. The spleen is concerned in various ways in the occurrence of such a hematologic change. The dicreases in the number of blood cells and in the amount of hemoglobin which occurs in the presence of a mechanism of obstruction in the portal system has been ascribed by many workers to inhibited bone marrow activity on the hypothesis of Bock and Frenzel. However, our experimental perfusion of the spleen, an experiment repeated over many years, has directly demonstrated that the spleen functions by reacting conditionally-the conditional reaction of splenic function-showing that the mechanism by which a hematologic change is brought about in splenomegaly admits of no arbitrary explanation before the presence or absence of splenotoxin is ascertained.
4. Pathologic physiology of portal circulation
As seen in its three-dimensional morphological picture, liver cirrhosis of different types develops under various circumstance, all related to portal hypertension. And yet the liver is not the only agent to be taken into account in the study of portal hypertension. Our simultaneous oncometry of the liver and spleen has made it clear that the liver and spleen change differently in size per c.c. after bloodletting and injection of adrenalin and histamin, clearly indicating that the two organs in the whole portal system control the portal circulation in different ways. The interrelationship between the liver and spleen is therefore to be kept in view in considering the pathophysiology of the portal circulation. This was a point clarified by the method we devised for simultaneous liver-spleen perfusion; we saw in dogs that the portal blood flow was increased and the portal pressure raised when two normal dog spleens or an extirpated pathologic human spleen were connected to a normal dog liver, that the portal system was hypertensive when a removed dog spleen was perfused with a fluid constant in volume and a normal dog liver was replaced with a dog liver with various stages of precirrhotic and cirrhotic changes produced in it. What was particularly noteworthy was the fact that there was a rise in the portal pressure even when the organic change of the liver was mild.
By the way, we were the first to find that sometimes splenectomy is followed by a patho-physiological phenomenon related to the dynamics of the portal circulation. We called attention to this phenomenon under the provisional name of postoperative splenic shock.
5. Factors affecting portal pressure
We observed in man and dog how the portal pressure was affected by thoracotomy, artificial pneumothorax, a rise in the internal pressure of the trachea, abdominal press, ephedrin injected, and by stimulation of the phrenic nerve, etc. A far greater rise in the portal pressure was brought about when the portal vein, its trunk in particular, was blocked, illustrating the deep significance of a portal thrombosis in the hernorrhage of the esophageal varices and as one cause of death following splenectomy.
6. Portal thrombosis
Portal thrombosis is closely related to pathological changes in the wall of the portal vein, depending particularly on the degree to which the intima is thickened. What is surgically significant is that the part it plays in a hemorrhage of esophageal varices depends largely on the particular area it occurs in. The frequency of occurrence of portal thrombosis is remarkably varied according as the system is blocked above the liver or below it , suggesting that the liver is concerned in its occurrence.
7. Pathology of collateral vessels, more particularly esophageal varices
We have investigated the collateral vessels running to the esophageal varices and emphasize the significance which the coronary vein of the stomach, its arc in particular, and the short gastric veins have in the interruption of the blood flow into the esophageal vances.
Postmortal varices are different from what they are in a living body. We devised an intraesophageal camera for taking a natural color picture of the esophageal varices and an apparatus with which puncture of a varix can be safely accomplished for examination of the relationship between the internal pressure of a varix and that of the portal vein. It was found as a result that the two pressures are approximately the same in value. (The manner a varix is punctured was shown in movies.)
8. Fluid dynamics considered mainly in relation to esophageal varices
The size of blood vessels, the speed of blood flow, and the viscosity of blood in the portal region, on the one hand, and the result of the interruption of the blood flow to esophageal varices by our method, on the other, have made it possible to formulate a rule of fluid dynamics in relation to esophageal varices in portal hypertension. The measurement made according to the rule makes it presumable that the pressure in an esophageal varix is reduced to one-eighth of its original value after interruption of the blood flow to esophageal varices by our method which consists in the simultaneous performance of splenectomy and extirpation of the arch of the gastric coronary vein. In fact, the lowest level to which the internal pressure of an esophageal varix went down after interruption of the blood flow was zero (the procedure causing death in 4% of 49 cases). The rule was found valid in a experiment in a series of models also. (This experiment was shown in movies.)
9. Conclusion
We warned that cancer arising from liver cirrhosis was geopathologically high in incidence (34.2%) in Japan.
We emphasized by way of conclusion that portal hypertension is a disease witch can be diagnosed at a relatively early stage from the sufficiently conspicuous pathologic changes to be noted in the esophagus on esophagoscopy, a procedure now in extensive use, and that those diseases accompanied with the functional impairment of the liver which is curable or the progress of which can be arrested by treatment should be identified and surgicaly treated at the ealiest possible stage, the operation being relatively simple and easy to perfom, and that portal hypertension will be treated with better result by such surgical measures.
(author's abstract)
To read the PDF file you will need Adobe Reader installed on your computer.