Portal vein thrombosis is a complete or partial occlusion of the trunk of the portal vein and its branches by thrombotic masses. Pathology is manifested by abdominal syndrome, vomiting, diarrhea, signs of portal hypertension (ascites, splenomegaly, dilation of venous collaterals), complicated by bleeding from the upper digestive tract, intestinal infarction and other conditions. The basis of the diagnosis consists of imaging methods – ultrasound, MR and CT angiography, venography of the affected areas. Therapeutic tactics involve anticoagulant therapy, thrombolysis, surgical correction.
I82.8 Embolism and thrombosis of other specified veins
Portal vein thrombosis (piletrombosis) is considered a fairly rare phenomenon, the risk of which does not exceed 1% in the general population. Its prevalence among patients with cirrhosis of the liver varies from 0.6 to 26%, which is apparently due to differences in sampling criteria and diagnostic methods. The disease is called the cause of 5-10% of cases of portal hypertension in residents of developed countries and up to 40% in the Asian region (due to the higher frequency of infectious pathology). The prevalence of primary thrombosis in adults and children is the same. There were no gender differences in the development of the disease, except for cirrhotic obstruction, which is more often diagnosed in men.
The disease has a multifactorial nature. Thrombosis develops under the influence of systemic and local disorders involved in damage to the vascular wall, increased coagulation, slowing venous blood flow. Among the most significant reasons are the following:
- Cirrhosis of the liver. It is the main etiological factor, accounting for 24-32% of cases of thrombotic occlusion. The probability of thrombosis increases in the later stages of the disease, if organ transplantation is necessary. The transition of cirrhosis to hepatocellular carcinoma increases the frequency of extrahepatic piletrombosis.
- Neoplasms. Malignant neoplasms of hepatic or pancreatic origin are the cause of 21-24% of cases of thrombosis. The development of pathology is mediated by compression or direct tumor invasion, concomitant hypercoagulation, hormonal shifts.
- Thrombophilia. Systemic disorders are caused by congenital coagulation defects – genetic mutations (Leiden factor V, prothrombin, plasminogen activator inhibitor), deficiency of proteins C and S, antithrombin deficiency. Acquired factors include chronic myeloproliferative pathology, antiphospholipid syndrome, paroxysmal nocturnal hemoglobinuria.
- Inflammatory diseases. The pathological process can occur against the background of abdominal inflammatory pathology (pancreatitis, cholecystitis, hepatitis), infectious diseases (malaria, typhoid fever, amoebiasis). In children and newborns, half of the cases of thrombosis account for omphalitis, umbilical sepsis, appendicitis.
- Injuries and surgical interventions. The portal vein is damaged by abdominal injuries and surgical interventions on abdominal organs (splenectomy, cholecystectomy, liver transplantation). Pathology occurs after portosystemic bypass surgery, fine needle aspiration liver biopsy, esophageal vein sclerotherapy.
Other risk factors for portal vein thrombosis include pregnancy, oral contraceptives, hypercholesterolemia. The role of intra-abdominal adenopathy, systemic inflammatory response syndrome was noted. In childhood, occlusion occurs with congenital anomalies of the vascular system (defects of the interventricular and atrial septa, deformation of the vena cava) and biliary tract. The cause of 10-30% of thrombotic stenoses remains unclear.
Based on modern concepts, portal vein thrombosis is the result of systemic coagulopathies (hereditary, acquired) and the action of local factors. Damage to the vessel wall by a tumor, invasive procedures or injuries is characterized by cytokine production, activation of thromboxane A2 and thrombin, increased adhesion and platelet aggregation. Venous stagnation during external compression is accompanied by endothelial hypoxia, accumulation of activated coagulation factors. All this triggers the formation of a parietal blood clot with its further increase.
Vascular occlusion is accompanied by portal hypertension, which leads to changes in systemic and intra-organ hemodynamics. The liver loses about 2/3 of its blood supply, but this is compensated by dilation of the hepatic artery and the rapid development of a network of collaterals. A cavernoma forms around the thrombosed vein, and it itself turns into a fibrous cord. The newly formed vessels are located within the bile ducts and bladder, pancreas, antrum of the stomach, duodenum.
The pathogenesis of thrombosis in hepatic cirrhosis is not completely clear. Portal hypertension with slowing of blood flow through the portal vein, peripheral lymphangiitis, and periportal fibrosis are of great importance. Systemic blood bypass provokes hemosiderosis, hepatocytes in hypoperfusion zones undergo apoptosis. Stagnation is detected in the small and large intestines above the level of occlusion, and gastropathy is detected in the stomach. Mesenteric ischemia can lead to the transition of the thrombotic process to mesenteric segments.
There is no formal classification of portal vein thrombosis. According to the clinical recommendations for portal hypertension, when making a diagnosis, the site of thrombosis and its manifestations, the presence and nature of the underlying disease, the degree of occlusion (partial, complete), the involvement of extrahepatic segments are taken into account. Depending on the location of the thrombus , several forms of pathology are distinguished:
- Stem (trunkular). The occlusion site is located in the trunk of the portal vein, distal to the confluence of the splenic and upper mesenteric. Occurs primarily or by spreading from the root segment.
- Radicular (radicular). It is characterized by a lesion of the root branches – the splenic vein and mesenteric vessels.
- Terminal. Portal vein thrombosis spreads to intrahepatic branchings and capillaries, accompanied by small or developed collaterals.
The presented classification makes it possible to assess the consequences of thrombotic obstruction and the patient’s ability to work. When the interstitial vessels are first affected, and then the large trunks, an ascending (primary) process is established. Mesenteric thrombosis, which occurs due to obstruction of the portal or splenic veins, is called descending (secondary). In clinical phlebology, acute, subacute and chronic stages are also distinguished, successively replacing each other.
The clinical picture of portal vein thrombosis is determined by the origin, degree, extent, localization, rate of occlusion, severity of collaterals. Partial thrombosis is asymptomatic, being detected only with instrumental diagnosis, complete obstruction (90-100% of the lumen) is characterized by rapid development in a few days. The subacute form progresses for 4-6 weeks, and the chronic process is characterized by a slow increase in symptoms (from several months to a year).
Acute stem piletrombosis is manifested by sharp pains in the right hypochondrium and epigastrium, combined with flatulence, frequent vomiting, diarrhea (often with an admixture of blood). Signs of portal hypertension are rapidly increasing – dilation of subcutaneous, esophageal, hemorrhoidal veins, ascites. Jaundice and liver function insufficiency are often detected. The general condition of patients quickly becomes severe, which is mainly due to recurrent bleeding from the gastrointestinal tract.
Radicular thrombosis at the level of the splenic segment begins acutely, with pain in the left hypochondrium, bloody vomiting and tar-like stools. Enlargement of the spleen and subfebrile fever are combined with the usual size of the liver. In the subacute period, splenomegaly, ascites gradually increase, the venous network on the abdomen expands. The terminal form of pathology is detected only with a widespread lesion – in such patients, an enlarged spleen and wide subcutaneous collaterals are usually determined.
Chronic piletrombosis has no specific manifestations. Lack of appetite and general weakness are sometimes the only symptoms of the disease. Subcutaneous anastomoses and moderate ascites are detected in most patients. In 20-40% of cases, pathology manifests itself by bleeding from varicose extensions of the esophagus. Sluggish variants of portal vein thrombosis are characterized by an indistinct pain syndrome, subfebrility, sensitivity of the liver during palpation. Splenomegaly with signs of hypersplenism, heaviness in the hypochondrium, emaciation are noted.
The most dangerous consequence of acute occlusion of mesenteric vessels is intestinal infarction with the development of peritonitis and multiple organ failure (typical for 5% of cases). Most of the complications of long-term piletrombosis are caused by portal hypertension. The expansion of the esophageal veins in many patients is accompanied by bleeding, the risk of which is 100 times higher with cirrhosis of the liver. Pronounced portosystemic bypass surgery leads to hepatic encephalopathy, secondary changes in the biliary tract (portal biliopathy, cholangiopathy). With persistent risk factors, thrombosis may recur, complicated by embolization.
The absence of specific signs of thrombosis, the need to determine the prerequisites, level, degree and consequences of the lesion create the need for a comprehensive examination of the patient. The diagnostic program is based on instrumental visualization methods:
- Ultrasound of the portal vein. Having a high specificity (60-100%), it is recognized as the method of choice for primary diagnosis. Ultrasound determines a heterogeneous focus of increased echogenicity with fuzzy contours, partially or completely overlapping the vascular lumen. Doppler mapping makes it possible to identify the absence of blood flow in the vein and its tributaries, the presence of portosystemic shunts, cavernomatous transformation.
- CT and MR angiography of vessels. CT with contrast gives accurate information about the state of venous walls, the extent of thrombosed areas, the presence of perivisceral collaterals, varicose veins in the retroperitoneal space. Magnetic resonance angiography is used to determine the consistency of portal blood flow, to assess the lumen of shunts – its results are more reliable than UZDS.
- Portal venography. It is used in cases when it is not possible to confirm or exclude thrombotic lesion by noninvasive methods. Contrast venography reveals not only stenoses, but also filling defects from external compression. However, with the established patency of the vessel, it is not necessary.
When diagnosing piletrombosis, phlebologists pay attention to coagulogram indicators (an increase in fibrinogen, prothrombin index, slowing of blood clotting time), low antithrombin levels. FGDS allows to identify varicose veins of the esophagus, it is possible to exclude cirrhosis thanks to elastography and liver biopsy. Differential diagnosis is carried out with hepatic schistosomiasis, thrombosis of the inferior vena cava, compressive pericarditis, restrictive cardiomyopathy.
The objectives of therapeutic correction are to restore the patency of the vessel, prevent the progression of pathology, eliminate complications of venous hypertension. Based on the severity of the process, the patient’s age, etiological and other factors, a combination of conservative and radical methods is used:
- Anticoagulant therapy. It is the best way to recanalize the venous lumen, but there is no consensus on its use. The duration of treatment with anticoagulants (low molecular weight heparins, oral agents) in persons with acute piletrombosis ranges from 3 to 6 months, and in chronic it is decided individually.
- Introduction of thrombolytics. Regional thrombolysis (administration of streptokinase, alteplase, tenecteplase) by transhepatic or transjugular access allows for recanalization, avoiding the side effects of anticoagulant therapy. In acute total or subtotal occlusion, systemic thrombolysis can be performed.
- Surgical methods. If conservative measures are ineffective, distal splenorenal bypass surgery is the operation of choice. In conditions of impaired patency of the splenic area, mesentericoportal or mesentericocaval anastomosis is applied using vascular prostheses.
Esophageal varicose veins are treated with ligation, endoscopic sclerotherapy. In urgent situations with bleeding, azigoportal dissociation operations can be performed (gastrotomy with stitching of the lower third of the esophagus, devascularization of the stomach). Severe hypersplenism requires splenectomy.
Prognosis and prevention
In general, the prognosis for the disease is relatively favorable. Clots can undergo aseptic autolysis, organization, and vascularization. The ten-year survival rate for adults reaches 60%, and the overall mortality rate is less than 10%. In the presence of cirrhosis and malignant neoplasms, the prognosis worsens. Sometimes blood clots turn into emboli, become a source of sepsis. But timely and intensive treatment leads to recanalization of the vessel, which is accompanied by a complete clinical recovery. Prevention of relapses is carried out by prescribing anticoagulants.
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