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Portal vein thrombosis PVT is a relatively common complication in patients with liver cirrhosis, but might also occur in absence of an overt liver disease. Several causes, either local or systemic, might play an important role in PVT pathogenesis.
Portal vein thrombosis: Insight into physiopathology, diagnosis, and treatment
Frequently, more than one risk factor could be identified; however, occasionally no single factor is discernable. In this review, we analyze the physiopathological mechanisms of PVT development, together with the hemodynamic and functional alterations related to this condition.
Moreover, we describe the principal factors most frequently involved in PVT development and the recent knowledge concerning diagnostic and therapeutic procedures.
The term portal vein fe PVT refers to the complete or partial obstruction of blood flow in the portal vein, due to the presence of a thrombus in the vasal lumen[ 1 ]. Although in the general population PVT is considered a rare event, its prevalence among cirrhotic patients ranges between 4.
The first case of PVT was reported in by Balfour and Stewart, describing a patient presenting splenomegaly, ascites, and variceal dilation[ 3 ]. Several etiological causes, either of local or systemic origin, might be responsible for PVT development, although more than one factor is often identified. Furthermore, PVT clinical presentation is different in the context of acute or chronic onset and depends on the development and the extent of a collateral circulation.
Intestinal congestion and ischemia, with abdominal pain, diarrhea, rectal bleeding, abdominal distention, nausea, vomiting, anorexia, fever, lactacidosis, sepsis, and splenomegaly are common features of acute PVT. In contrast, chronic PVT can be completely asymptomatic, or characterized by splenomegaly, pancytopenia, varices, and, rarely, ascites[ 3 ]. In the presence of portal hypertension, PVT must always be investigated, especially in cirrhotic patients, even if it is considered a rare event[ 2 ].
Indeed, an early diagnosis and appropriate cavernpma of secondary portal caveroma could be, in some cases, life-saving for the patient. Furthermore, in the diagnostic iter, the identification of possible local or systemic trigger factors is of primary importance however, occasionally no single factor is discernable.
Malformación cavernomatosa de la vena porta
Currently, several therapeutic options are available; however, their feasibility and efficacy are still being evaluated and the risks and benefits should be carefully considered for each patient. In this review, we discuss the features of PVT, pointing out new insights into clinical, diagnostic, and therapeutic issues, making an overview of current beliefs regarding patient outcome and, finally, reporting controversies about the correct management of PVT in the setting of liver transplantation.
As pora consequence of portal vein obstruction, systemic and splanchnic hemodynamics undergo specific and important modifications[ 4 ].
On the cessation of cavernoja blood flow, the liver portw about two thirds of its blood supply. Interestingly, this condition is usually well tolerated and patients are often asymptomatic, while an acute arterial obstruction always leads to a severe hepatic dysfunction, which is sometimes fatal. This vascular neo-formation begins in a few days after portal vein obstruction, and finalizes within 3 to 5 wk[ 67 ]. Usually, the original portal vein becomes a thin, fibrotic cord, which is difficult to visualize[ 89 ].
At this stage, the development of a hyperkinetic circulation, characterized by low systemic vascular resistance and a high cardiac output, is common[ 3 ]. Despite the activation of this complex system of support, the impairment of portal flow has important consequences on liver tissue.
It has been demonstrated in rats, that the progressive obliteration of the portal vein stimulates apoptosis of hepatocytes in the hypoperfused lobe[ 10 ], while increasing the mitotic activity in the normal perfused one. The latter effect is well known, and is employed therapeutically in resective liver surgery. However, this process results in a progressive loss of tissue and might be responsible for the impairment of hepatic synthetic function observed in advanced stages of portal vein obstruction[ 11 ].
The concept of PVT as a rare disease is mainly based on clinical series and case reports[ 2 ]. Cohen et al[ 13 ] confirmed these data and reported that most PVT patients were cirrhotics with a primary or metastatic liver cancer. Today, thanks to the availability of more sensitive and less invasive imaging, together with the existence of curative or palliative procedures, PVT is routinely investigated and recognized without any difficulty[ 14 – 16 ]. Thus, PVT seems more frequent than expected: The incidence among cirrhotic patients is still unknown, but recent data suggest a prevalence of about 0.
Several causes can be involved in the pathogenesis of PVT and, frequently, more than one coexist. Most frequent local risk factors for PVT[ 38917186479 ]. Portal vein thrombosis; TIPS: Transjugular intrahepatic portosystemic shunt. Most frequent systemic risk factors for PVT[ 38917186479 ].
Inflammatory abdominal foci such as appendicitis, diverticulitis, inflammatory bowel diseases, pancreatitis, cholecystitis, hepatic abscesses, and cholangitisliver cirrhosis or tumors, represent the most common local thrombotic risk factors[ 81218 ].
Direct vascular invasion, compression by tumor mass, or a hypercoagulable state are the mechanisms involved in neoplastic PVT development; hormonal factors might also play a role in this process, especially in men[ 162021 ]. Other less common PVT local causes are adenopathy, systemic inflammatory response syndrome, and surgical traumas to the portal venous system, such as portosystemic shunting, splenectomy, liver transplantation, ablative therapy for HCC, and fine needle aspiration of abdominal masses[ 1 ].
Prevalence of thrombotic risk factors in series of routinely investigated, consecutive adult patients with non tumorous and non cirrhotic, acute or chronic, PVT[ ].
The role of protein S PS and antithrombin III AT deficiency in PVT etiology has not yet been confirmed, and it is difficult to evaluate the influence of anticoagulation therapy on the impairment in liver function.
Indeed, in cirrhotic patients it is hard to distinguish between congenital and acquired deficiencies of natural coagulants and their role in PVT pathogenesis, because if liver function is impaired, levels of coagulation inhibitors, as well as those of pro-coagulation factors, are often decreased[ 27 ]. In contrast, a distal spleno-renal shunt or an H-type meso-caval shunt, in the same condition, didnot seem to be equally effective, probably due to insufficient residual portal vein flow and the consequent impairment in liver synthetic function[ 29 ].
However, the relatively low prevalence of genetic, in respect to acquired, thrombophilic disorders, might represent a potential diagnostic matter in PVT patients, and should be considered carefully in clinical practice[ 30 ]. Unfortunately, in practice, this policy is not applicable without difficulty. Among the other thrombophilic disorders, a prothrombin gene mutation seems to be frequent among cirrhotics with PVT[ 231 – 34 ].
However, in the general population, its role in PVT development seems less clear, as it is considered a weak prothrombotic risk factor. Moreover, a homozygous methylene tetrahydrofolate reductase MTHFR gene mutation might be associated with PVT development alone or, if heterozygote, in the presence of other cofactors[ 1335 – 39 ].
Furthermore, the presence of anticardiolipin antibodies is quite frequent in patients with chronic liver disease; a transient positivity is often reported after infections, suggesting a relationship between microorganisms i. Bacteroides species and thrombotic events, such as PVT[ 40 – 43 ]. In contrast, other studies consider anticardiolipin antibodies simply as an epiphenomenon of liver damage[ 4144 ]. Finally, the role of oral contraceptives, steroids, and pregnancy is still less clear[ 45 – 47 ].
The principal diagnostic criteria are usually incompletely met in these patients, probably because of the atypical manifestation of the disease[ 50 ]. Occasionally, it is not possible to recognize any overt cause of PVT; generally, the clinical course is favorable for these patients, with a low incidence of complications. In conclusion, it is reasonable to routinely investigate the venx common prothrombotic disorders and exclude a local trigger, to provide a correct management of PVT and its original cause.
However, the mechanism of PVT development is complex and multifactorial, and is not always attributable to a single risk factor.
In the presence of sporadic local or systemic promoting events, an underlying intrinsic predisposition might be the access key to thrombosis development[ 113 ]. PVT onset can be acute or chronic. This is an arbitrary distinction, which is sometimes difficult to apply in clinical cavernnoma patients who develop symptoms, such as abdominal pain, nausea, and fever, within sixty days prior to hospital admission, might have an acute PVT development[ 5859 ].
PVT can be classified into four categories, depending on the extension: In fact, when thrombosis is extended to both portal and mesenteric veins, the risk of bowel ischemia is considerable and mortality high, despite a pota risk of variceal bleeding[ 61 ].
PVT can occur either in childhood or in adulthood, with the same incidence[ 45 ]. Clinical presentation always vnea on the onset and the extent of the thrombosis and the development of collateral circulation[ 62 ]. Intestinal congestion and ischemia are typical manifestations of acute PVT; abdominal pain or distention, diarrhea, rectal bleeding, nausea, vomiting, anorexia, fever, lactacidosis, splenomegaly and sepsis vema be variably present[ 6364 ].
If the obstruction is not resolved quickly, intestinal perforation, peritonitis, shock, and death from multiorgan failure might occur[ 8 ]. On physical examination, the abdomen venna be distended, but guarding is rare, except in case of intra-abdominal inflammation, intestinal infarction, and perforation[ 22 ]. The majority of patients exhibit ls, while ascites is rare or, eventually, present before the development of a collateral circulation. This mild, czvernoma, ascites is due to intestinal venous congestion in the absence of the mechanisms activated in liver cirrhosis[ 6364 ].
On the other hand, chronic PVT can be nearly asymptomatic, except for the presence of varices, cutaneous collaterals, or ascites[ 62 ]. Typically, patients with an advanced thrombosis do not always remember any previous trigger event or disease[ 226364 ]. As this phenomenon is strictly time-dependent, it is advisable to screen all PVT patients endoscopically, at diagnosis[ 63 ].
Portal vein thrombosis: Insight into physiopathology, diagnosis, and treatment
In cirrhotics with PVT, the risk of variceal bleeding is nearly times higher than in patients without liver disease, although the outcome seems better[ 6566 ]. Furthermore, hypersplenism and, consequently, pancytopenia, are commonly present in chronic PVT[ 1 ]; however, if one branch of the portal vein is preserved and the portal pressure is quite normal, they may even be absent.
Ascites and encephalopathy are uncommon and re transient. They are more frequent after an episode of gastrointestinal bleeding or associated with renal failure or sepsis in older patients[ 86467 ].
Nowadays, in developed countries, PVT is usually recognized at an early stage; cavernomatous transformation or the occurrence of gastrointestinal bleeding are rare. The clinical suspicion is often based on the incidental finding poeta hypersplenism, signs of portal hypertension or, less frequently, symptoms of portal cholangiopathy.
Doppler imaging can confirm the absence of flow in part or all the vasal lumen, and, if present, a cavernomatous transformation[ 22 ]. It appears to be more accurate than US or computed tomography CT scans in discovering portal invasion by tumors[ 7778 ].
However, the limit of Cavernoms is the presence of a relatively blind area, which cannot be investigated, involving the distal superior mesenteric vein and the intrahepatic portion of the portal vein[ 76 ].
Complete thrombosis of the portal vein trunk ultrasonography ; B, C: Thrombosis of the cavernoka portal vein CT scan ; E, F: Thrombosis of the right portal vein MRI. Recanalization of paraumbilical vein CT scan ; E: Perigastric and paraesophageal varices CT scan.
Cavernomatous transformation of the portal vein. Incidentally, US is less reliable in determining the extension of the thrombus to the mesenteric circulation[ 79 ]. CT scanning is able to demonstrate hyperattenuating material in the portal vein lumen and the absence of enhancement after contrast injection. In addition, in prta areas, hepatic enhancement appears increased during the arterial phase and decreased during the portal phase. CT is also useful for the identification of the possible cause of the thrombosis or potential complications, such as bowel ischemia and perforation[ 22 ].
MRI cavfrnoma also confirm the vascular occlusion; at spin-echo MR, the clot appears isointense on T1- weighted images, or hyperintense if recent, vnea usually has caverjoma more intense signal on T2 images. Gradient-echo Ed might help to better evaluate any confusing spin-echo MR image[ 80 ].
Furthermore, contrast-enhanced MR angiography is useful to assess flow direction in the portal venous system pporta its patency, to identify a cavernomatous transformation, to determine the presence of varices, and to verify the correct function of surgical shunts[ 8182 ].
In addition, MR angiography has a high accuracy in the follow-up of the portal venous system before and after liver transplantation[ 82 – 85 ].
Moreover, MRI-true fast imaging with steady state precession true FISPmight overcome the difficulty ve contrast injection in cases of poor venous access and the degradation of the images by respiratory motion[ 86 ]. In PVT patients, liver function is typically conserved.
Laboratory investigations will be normal or quite normal, unless there is coexistence of a liver disease. However, levels of prothrombin and other coagulation factors could be moderately decreased, while D-dimer is usually increased[ 822 ].