Thrombosis and Embolism of the Portal Vein; Stenosis; Pylephlebitis

IV. Diseases of the Portal Vein.

DEFINITION.—By the terms at the head of this section are meant the various pathological processes which induce coagulation of the blood in some part of the portal system. As the portal vein is made up of many branches coming from the various organs of the abdominal cavity except the kidneys, and as it empties, so to speak, into the liver, it is obvious that various and complex derangements will ensue on the formation of thrombi.

CAUSES.—Thrombosis of the portal vein occurs under three general conditions: the blood is in a readily coagulable state; the action of the heart is weak and the blood-current sluggish; the circulation through the vein is impeded by external pressure. The coagulability of the blood is increased in diseases characterized by an excess of its fibrin-producing constituents, of which cirrhosis of the liver may be mentioned as one having this peculiarity. In chronic maladies of a depressing kind there may be simply a weak action of the heart, or the muscular tissue of the organ may be affected by a fatty and atrophic degeneration. The external pressure by which the blood-current through the vein is impeded may be caused by the newly-formed connective tissue of Glisson's capsule, by enlarged lymphatics in the hilus of the liver, or by tumors of various kinds. The first named of these causes of compression—atrophic cirrhosis—is most frequently acting. Very rarely, organized exudations of the peritoneum may be so situated as to compress the portal vein. This result can only happen when the hepatic portion of the peritoneum is involved.

Pylephlebitis exists in two forms: the adhesive and suppurative. The former results in changes not unlike those of simple thrombosis. The blood coagulates in the affected part of the vessel, the clot is organized, and the vessel ultimately forms a solid rounded cord which is permanently occluded. The suppurative variety is so different in its origin and in its results that it requires separate treatment, and I therefore postpone the consideration of it to the next section.

SYMPTOMS OF THROMBOSIS AND ADHESIVE PYLEPHLEBITIS.—It is a remarkable fact that the biliary function of the liver is not necessarily affected in cases of occlusion of the portal vein. It is true, in advanced cases of cirrhosis, when the interlobular veins are obliterated by the pressure of the contracting newly-formed connective tissue, the functions of the liver are arrested in so far as the damage thus caused extends. Notwithstanding the blocking of the portal, sufficient blood reaches the hepatic cells by the anastomosis between the hepatic artery and the interlobular veins—an anatomical connection demonstrated by Cohnheim and Litten. So long as this anastomosis continues bile will be formed, although the portal vein is occluded.

Virchow's Archiv, Band lxvii. p. 153, "Ueber Circulationsstörungen in der Leber."

The most significant symptoms of thrombosis of the portal vein are the sudden formation of ascites, which quickly assumes a very high grade, and equally sudden passive congestion of the gastro-intestinal mucous membrane, enlargement of the spleen, and distension of the superficial veins of the abdominal parietes. When these symptoms succeed to cirrhosis of the liver, or appear after the formation of a tumor in the hepatic region, or come on in the course of phthisis or chronic inflammation of the hepatic peritoneum, the existence of thrombus of the portal vein may be reasonably suspected.

Coincidently with the occlusion of the portal vein the gastro-intestinal mucous membrane becomes the seat of a catarrhal process, and to the fluid thus produced is added a much more abundant transudation from the distended capillaries. Nausea, vomiting, and diarrhoea result, the rejected matters being serous, watery, and in many cases tinged with blood. Now and then quite a severe hemorrhage takes place, and the blood is brought up by vomiting (hæmatemesis) or is discharged by stool. Hemorrhoids form, and, in large masses protruding, much pain is experienced, and free bleeding may result from rupture of a distended vein.

The veins of the abdominal parietes, which in the normal state are invisible or at least not prominent, and which form anastomoses with the portal, when the obstruction occurs dilate, sometimes to a remarkable extent. The most important anastomosis is that between the femoral and saphena and internal mammary and epigastric veins. When the hepatic branches of the portal are closed, but the trunk remains pervious, the parumbilical vein enlarges greatly, and, communicating with the superficial veins of the anterior part of the abdominal walls, forms a radiating network of tortuous veins to which is given the striking title of caput Medusæ.

The most significant symptom of portal thrombosis is a quickly-forming ascites. It is true, ascites is a common symptom in advanced cirrhosis, but the rapid accumulation of fluid and the prompt filling of the cavity after tapping distinguish that which arises from portal thrombosis from all others. Besides its excessive extent, the ascites presents the usual symptoms.

Due to the same cause as the enlargement of the superficial veins, the hemorrhages, the ascites, etc., there occurs considerable hypertrophy of the spleen in many of the cases. It sometimes happens that the new compensatory circulation and the hemorrhages from some part in the usual route of the portal so dispose of the blood that the spleen does not enlarge sufficiently to be readily made out.

COURSE AND TERMINATION.—It is obvious that a condition such as that induced by thrombosis of the portal must be comparatively quickly fatal; but the cases vary in duration as the compensatory circulation is more or less complete. Whilst the majority of cases terminate within two weeks, instances of several months' duration are not unknown, but a fatal termination, sooner or later, is inevitable in all cases.

Coming on in the course of some chronic affection of the liver or some obstructing cause exterior to the organ, there soon follow ascites, nausea and vomiting, hæmatemesis, bloody stools of a liquid character, enlargement of the spleen, distension of the abdominal veins, and the distressing symptoms produced by an excessive accumulation of fluid in the peritoneal cavity.

DIAGNOSIS.—As there is no symptom of thrombosis of the portal which may not be caused by advanced cirrhosis, the diagnosis rests on the rapid production of the attendant phenomena and their conjoint appearance.

TREATMENT.—A symptomatic treatment is alone possible. The highly irritable and congested intestinal mucous membrane precludes the employment of hydragogue cathartics. Salines which cause outward diffusion from the vessels are the only cathartics which can be used with propriety. Action of the kidneys and of the skin must be maintained. To this end the resin of copaiba in pilular form and pilocarpine subcutaneously may be used. If the strength of the patient will permit, leeches around the anus can be applied, and much relief may be expected from free bleeding. It is probable that opening a swollen hemorrhoid would give the same kind of relief as that caused by a free hemorrhage. In any case the benefit derived from treatment must be merely palliative and temporary.