Postgrad Med J: first published as 10.1136/pgmj.39.451.299 on 1 May 1963. Downloaded from POSTGRAD. MED. J. (I963), 39, 299 PORTAL HYPERTENSION AND ITS RADIOLOGICAL INVESTIGATION J. H. MIDDLEMISS, M.D., F.F.R., D.M.R.D. F. G. M. Ross, M.B., B.Ch., B.A.O., F.F.R., D.M.R.D. From the Department of Radiodiagnosis, United Bristol Hospitals PORTAL hypertension is a condition in which there branch of the portal vein but may drain into the right is an blood in the branch. abnormally high pressure Small veins which are present on the serosal surface portal system of veins which eventually leads to of the liver and in the surrounding peritoneal folds splenomegaly and in chronic cases, to haematem- draining the diaphragm and stomach are known as esis and melaena. accessory portal veins. They may unite with the portal The circulation is in that it vein or enter the liver independently. portal unique The hepatic artery arises normally from the coeliac exists between two sets of capillaries, i.e. the axis but it may arise as a separate trunk from the aorta. capillaries of the spleen, pancreas, gall-bladder It runs upwards and to the right and divides into a and most of the gastro-intestinal tract on the left and right branch before entering the liver at the one hand and the sinusoids of the liver on the porta hepatis. The venous return starts as small thin-walled branches other hand. The liver parallels the lungs in that in the centre of the lobules in the liver. They join inter- it receives a blood supply from an arterial source, lobular branches which coalesce and finally unite to by copyright. the hepatic artery, and a venous source, the form two or three hepatic veins which enter the inferior vein. vena cava just before it terminates in the right auricle. portal The liver lobules each have a small hepatic vein in the centre and in defined areas round the periphery there The Portal Circulation are portal tracts each of which contains a radicle of the Blood passes from the splanchnic arteries into the portal vein, hepatic artery and a small bile duct. The spleen, pancreas, gall-bladder, stomach and intestines hepatic cells are arranged in sheets which are traversed from branches of the abdominal aorta. From the sinuses by the sinusoids so that one-cell-thick plates of hepatic in the splenic pulp, the blood is collected into several cells are formed. These plates form an irregular sponge tributaries which unite at the hilum of the spleen to form which surrounds spaces or lacunae in which the sinusoids are connective tissue the splenic vein, which runs to the right along the upper suspended by fibrils. Between http://pmj.bmj.com/ posterior aspect of the pancreas to the region of the neck individual hepatic cells are bile canaliculi from which of the pancreas. As it crosses the upper abdomen, it bile passes to collecting ductules which run to the portal receives as tributaries the short gastric veins, the left tracts. Here small bile ducts are formed which drain gastro-epiploic, pancreatic, inferior mesenteric and left eventually into the extra-hepatic bile ducts. gastric veins. The superior mesenteric vein is formed in The sinusoids are thus modified capillaries lined with the root of the mesentery from union of the jejunal and endothelial cells on a basement membrane and some of ileal veins, the ileo-colic, right and middle colic and their cells are specially adapted reticulo-endothelial cells inferior pancreatico-duodenal veins. The portal vein known as Kupffer cells. The sinusoids form a honey- usually forms behind the neck of the pancreas, but comb or 'hepatic labyrinth' in the lobules which through on September 24, 2021 by guest. Protected occasionally in front of the pancreas, by the union of the blood flows from the peripheral portal vein to the central superior mesenteric and splenic veins at the level of the hepatic vein. The hepatic artery divides into fine body of the second lumbar vertebra. The portal vein branches in the portal tracts which form a capillary net- runs upwards and to the right, but occasionally hori- work that drains into the portal vein and peripheral zontally, in the free edge of the lesser omentum, behind sinusoids. Some hepatic artery blood enters the sinusoids the duodenal bulb and common bile duct, to terminate direct and it has been shown histologically that these at the porta hepatis where it divides into two and some- small hepatic arterioles contain muscle pads and ring times three branches, which pass into the liver. The muscle in their walls which presumably control the terminations of the left gastric and inferior mesenteric hepatic artery blood flow. The principle of the lobule veins are variable. In two-fifths of persons they enter the as a structural unit involves complete separation of the splenic vein; in a further two-fifths they enter the portal portal and hepatic veins, the terminal branches of which and superior mesenteric veins respectively, and in the interdigitate with lobular parenchyma interposed in all remaining one-fifth the left gastric vein enters the junc- places between them. However, anastomoses betweer tion of the portal and splenic veins and the inferior them have been claimed and are supposed to be open in mesenteric the junction of the superior mesenteric and the absence of digestion. splenic veins. In about 90% of people several veins The liver is surrounded by the hepatic capsule from enter the portal vein including the pyloric vein on the which a connective tissue stroma extends into the portal left side and the cystic and superior pancreatico- tracts and the central canals. Within the lobule, radial duodenal veins on the right side. Para-umbilical veins collagenous fibres connect the central part of the lobule from the falciform ligament usually drain into the left to the periphery and a fine reticulum supports the Postgrad Med J: first published as 10.1136/pgmj.39.451.299 on 1 May 1963. Downloaded from 300 POSTGRADUATE MEDICAL JOURNAL IVfay I963 sinusoids. On the surface of the liver interlobular an incidental post-mortem finding. The hepatic connective tissue unites with the capsule and through veins are occluded at their this connection capsular vessels communicate with the usually partially point portal vein but not the hepatic vein. of union with the inferior vena cava, thrombosis The total liver blood flow is about 1,500 ml./min. either spreading from the inferior vena cava or in adults, of which about 80% is contributed by the occurring primarily in their ostia; it is most portal vein. The liver blood flow can be measured by the to some other disease such bromsulphthalein excretion method or by radio-active commonly secondary isotopes. as pressure or invasion by hepatic neoplasms. The portal pressure can be measured at laparotomy by connecting a saline manometer to a cannula inserted Obstruction into an unobstructed vein of the portal system: the (b) Intra-hepatic fact that the abdomen is open probably makes very little The low pressure gradient between the portal difference to the reading. It has been shown, however, and hepatic veins results in easy obstruction that the intrasplenic pressure is a relatively accurate to the blood flow. The obstruction indication of the portal venous pressure, though naturally portal may it is slightly higher than the pressure in the portal vein be temporary or permanent. itself. This is estimated by percutaneous needle punc- Any condition that causes tension in the ture, usually in combination with trans-splenic portal capsule, such as acute hepatitis, will probably venography. Another indirect method is to estimate the obstruct the blood flow wedged hepatic vein pressure by passing a cardiac portal temporarily leading catheter through the right auricle into the inferior to portal hypertension but the pressure returns vena cava and thence into an hepatic vein. The catheter to normal when the lesion resolves. tip is passed out into the liver so that its external A longer-standing portal hypertension arises circumference blocks the internal circumference of an in conditions which result in a fibrous hepatic vein. response Normal portal pressures are: in the liver, and hepatic cirrhosis is considered Intrasplenic .. 3 to 17 mm. Hg to be the main cause of intra-hepatic obstruction. Portal vein .. 7.5 to I6 ,, No matter what the cause of the cirrhosis, the Sinusoidal .. 6 to 8 ultimate histological picture varies little. Portal Temporary occlusion of the portal vein in normal in cirrhosis is obstruc- persons causes the portal venous pressure to rise hypertension produced by by copyright. immediately to 40 to 50 mm. Hg and it remains at this tion of the portal vein branches by fibrosis; by level so long as the obstruction is maintained. pressure by regenerating liver nodules on the small hepatic veins and by presinusoidal anasto- Portal Hypertension moses between the hepatic artery and portal The portal venous pressure may be raised as vein in the fibrous septa of the cirrhotic liver a result of increased inflow through the splanchnic resulting in an increased hepatic artery blood flow. arteries or due to increased resistance to the The aetiological factors which may give rise to outflow from the of veins. Increased intra-hepatic portal obstruction may be listed portal system as follows: inflow is only likely to be significant if the inflow http://pmj.bmj.com/ resistance is diminished, which occurs in cases (i) Virus hepatitis.-Most cases of virus of splenic artery-vein fistulke. Increased resistance hepatitis resolve completely and do not lead to to the outflow of the portal venous blood is portal hypertension.