Splenic vein thrombosis (plural: thromboses) is an uncommon condition in which the splenic vein becomes thrombosed, that most frequently occurs in the context of pancreatitis or pancreatic cancer. Whilst, for the most part asymptomatic, splenic vein thrombosis increases risk of gastric varices and associated upper GI hemorrhage.
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Epidemiology
Patients with chronic pancreatitis account for 65% of all cases of splenic vein thrombosis, whilst pancreatic cancer, lymphoma, and propagated clots from the portal vein are other known causes 1,2. The condition can be seen in between 20% to 45% of patients with chronic pancreatitis depending on the study 3,4,8.
Clinical presentation
Most patients will present silently with no symptoms related to the splenic vein thrombosis although left-sided portal hypertension can occur 2,9. The condition can cause upper GI bleeding due to associated gastric varices 2-5. While presentation can also relate to abdominal pain secondary to splenomegaly 1, splenic vein thrombosis is more commonly diagnosed on imaging rather than the clinical triad of splenomegaly, normal liver enzymes, and upper GI bleeding 9.
Splenic vein thrombosis should be considered in the following patients 4:
- history of pancreatitis with newly diagnosed GI bleeding
- splenomegaly with no portal hypertension, cirrhosis, or hematologic disease
- isolated gastric varices
Pathology
The formation of a bland thrombus within any vessel occurs due to a disturbance in Virchow triad which can be summarized as flow disturbance, hypercoagulable state and endothelial dysfunction. In the case of thrombosis in the splenic vein, the most common association is pancreatitis or pancreatic neoplasm 1-4,8.
The proximity of the splenic vein to the pancreas causes it to be vulnerable to direct contact with peripancreatic inflammatory tissue 4. The mechanism for formation of the thrombus is likely complex with both intrinsic endothelial factors due to inflammatory or neoplastic processes, as well as possible extrinsic injury due to venous compression caused by fibrosis, pseudocysts, or edema 4.
Other contributing factors include trauma, malignancy, thrombocytosis, polycythemia, coagulopathies, pregnancy, oral contraceptives, and sepsis 1.
Radiographic features
The appearance of the thrombus itself will be identical to that of a portal vein thrombosis or SMV thrombosis on CT, ultrasound and MRI 2. Both the liver and the spleen may appear normal 7.
Fluoroscopy
Barium contrast studies may demonstrate thickened and tortuous mucosal folds or filling defects along the greater curvature of the stomach 4. These features correlate with gastric varices secondary to increased venous pressure.
Ultrasound
Ultrasound can be useful for evaluating splenic vein thrombosis 8. The modality has been quoted to have a sensitivity of 93% and a specificity of 83% 9.
A dilated thrombosed splenic vein with hyperechoic material present within the lumen may be demonstrated 1,8,9. There will be an absence of color flow in cases of total occlusion and retained residual flow in an incomplete clot on color Doppler 8. A patient with a normal flowing splenic vein seen on ultrasound is unlikely to have a splenic vein thrombosis 4. Other features possibly present include splenomegaly, dilated collateral veins, and cavernous transformation of the portal vein 1.
Given the relationship between pancreatitis and splenic vein thrombosis, there may also be stigmata of chronic pancreatitis present 6.
CT
CT may demonstrate an intravascular filling defect and potentially collateral circulation with possible cavernous transformation 9. CT will also likely demonstrate other features relative to the underlying etiology 8,9.
Treatment and prognosis
Anticoagulant therapy may be indicated in patients with hypercoagulable states 8. Revascularization only occurs in less than 20% of patients with an acute thrombus regardless of anticoagulation therapy however 3.
Splenectomy may also be indicated in patients with upper GI bleeding related to gastric varices 1,4,8. Doing so eliminates collateral venous return, thus decompressing varices 8. Isolated gastric varices secondary to splenic vein occlusion can be cured in 90% of cases with a low incidence of recurrent bleeding 2.
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