Splenic vein thrombosis overview

# Overview
Splenic vein thrombosis is the formation of a thrombus in the splenic vein. When thrombosis of the splenic vein occurs, collateral vessels develop to shunt blood around the occluded splenic vein. The two most common collateral pathways use the short gastric vessels. In the distal esophagus, portosystemic collaterals connect the short gastric veins into the azygous system. There is no established system for classification of splenic vein thrombosis. Common causes of splenic vein thrombosis are pancreatitis, pancreatic pseudocyst, pancreatic carcinoma, lymphoma, adenopathy from metastatic cancer, iatrogenic causes, splenectomy, partial gastrectomy, distal spleno-renal shunt, factor V Leiden mutation, prothrombin G20210A mutation. The incidence of  splenic vein thrombosis was estimated to be 14,100 cases per 100,000 individuals worldwide. Splenic vein thrombosis affects men and women equally. There is no racial predilection for splenic vein thrombosis. Most patients are asymptomatic, however, splenic vein thrombosis should be suspected in patients with a history of pancreatitis and  gastrointestinal blood loss, splenomegaly in the absence of portal hypertension, cirrhosis, and hematologic disease, in the setting of isolated gastric varices,  splenomegaly with rare leukopenia, thrombocytopenia, left upper quadrant and abdominal pain. Ultrasound, CT and MRI scans are important diagnostic modalities in the diagnosis of splenic vein thrombosis. Medical therapy for splenic vein thrombosis include anticoagulation to maintain INR between 2 to 3. The goal of anticoagulation is to prevent extension of the clot and to allow for recanalization. Splenectomy is recommended for all patients with bleeding varices associated with isolated splenic vein thrombosis. Splenectomy eliminates venous collateral outflow and decompresses surrounding varices.

# Historical Perspective
Thrombosis of the splenic vein is infrequently reported in literature, it is common knowledge among surgeons that this condition may follow splenectomy. In fact, local thrombosis at the site of ligation of the splenic artery and vein with extension back to the first branching vessel is to be expected after splenectomy. This degree of involvement of the splenic vein, however, should be asymptomatic, but it is potentially important because of possible extension into the portal venous system and as a source of emboli to the liver.

# Classification
There is no established system for the classification of splenic vein thrombosis.

# Pathophysiology
When thrombosis of the splenic vein occurs, collateral vessels develop to shunt blood around the occluded splenic vein. The two most common collateral pathways use the short gastric vessels. In the distal esophagus, portosystemic collaterals connect the short gastric veins into the azygous system. Splenoportal collaterals decompress the short gastric veins through both the coronary vein into the portal vein and via the gastroepiploic arcade into the superior mesenteric vein. In either case, the hypertensive short gastric veins cause increased pressure within the submucosal veins of the gastric fundus, resulting in varices.

# Causes
Common causes of splenic vein thrombosis are ancreatitis, pancreatic pseudocyst, pancreatic carcinoma, lymphoma, adenopathy from metastatic cancer. Some iatrogenic causes are splenectomy, partial gastrectomy, distal spleno renal shunt, Factor V Leiden mutation, prothrombin G20210A mutation.

# Differentiating Splenic vein thrombosis from Other Diseases
Splenic vein thrombosis  must be differentiated from hepatic vein thrombosis, portal vein thrombosis, testicular cancer, hyperhomocystenemia and deep vein thrombosis.

# Epidemiology and Demographics
The incidence of splenic vein thrombosis was estimated to be 14,100 cases per 100,000 individuals worldwide. Splenic vein thrombosis affects men and women equally. There is no racial predilection for splenic vein thrombosis.

# Risk Factors
Common risk factors in the development of  splenic vein thrombosis include abdominal cancer, liver cirrhosis, surgery, thrombophilias, hormonal treatments, myeloproliferative disorders, sickle cell anemia.

# Screening
There is insufficient evidence to recommend routine screening for splenic vein thrombosis.  However, routine screening of  splenic vein thrombosis after elective splenectomy is warranted because it allows the initiation of anticoagulant therapy to avoid further life-threatening complications. The incidence of splenic vein thrombosis is particularly high among patients operated on for lymphoma or with splenomegaly.

# Natural History, Complications, and Prognosis
If left untreated, patients with splenic vein thrombosis may progress to develop sinistral portal hypertension, gastric varices, ascites, splenomegaly, atraumatic splenic rupture.

# Diagnosis

## Diagnostic study of choice
Venous phase angiography accurately visualizes both the location of splenic vein obstruction and the routes of collateralization. The diagnosis of splenic vein thrombosis is confirmed on angiography when selective injection of the splenic artery shows non visualization of the splenic vein on delayed images.

## History and Symptoms
Most patients are asymptomatic, splenic vein thrombosis  should be suspected in patients with a history of pancreatitis and gastrointestinal blood loss, splenomegaly in the absence of portal hypertension, cirrhosis, and hematologic disease and in the setting of isolated gastric varices. Other signs  and symptoms are splenomegaly with rare leukopenia, thrombocytopenia, left upper quadrant pain and generalized abdominal pain.

## Physical Examination
Physical examination of patients with splenic vein thrombosis is usually remarkable for abdominal pain or distension, splenomegaly and signs of upper  gastrointestinal bleed.

## Laboratory Findings
Some patients with splenic vein thrombosis may have reduced hemoglobin / hematocrit  which is usually suggestive of gastrointestinal bleeding. Splenic vein thrombosis secondary to pancreatitis might have elevated levels of amylase and lipase. Some patients may have elevated liver function tests if the underlying cause is liver disease.

## Electrocardiogram
There are no ECG findings associated with splenic vein thrombosis.

## X-ray
There are no X-ray findings associated with splenic vein thrombosis.

## Ultrasound
Ultrasound is the best initial test for diagnosing splenic vein thrombosis. Accuracy may be limited by body size or location of veins. Endoscopic ultrasound appears to be a more accurate test than trans abdominal ultrasound for assessing patency of the splenic vein. Because EUS is a sensitive imaging tool for assessing small pancreatic cancers and determining vascular invasion, it should be considered when other tests have failed to confirm SVT as a cause of bleeding gastric or gastroesophageal varices.

## CT scan
CT scan is helpful in the diagnosis of Splenic vein thrombosis. Findings on CT scan in splenic vein thrombosis include an hyperattenuated material in the splenic vein, non-enhanced intraluminal filling defect.

## MRI
MRI in splenic vein thrombosis shows severely attenuated and partially calcified retro pancreatic splenic vein resulting in formation of a prominent gastroepiploic collateral channel between the superior mesenteric vein and the remnant splenic vein at splenic hilum along the greater curvature of stomach.

## Other Imaging Findings
There are no other imaging findings associated with splenic vein thrombosis.

## Other Diagnostic Studies
There are no other diagnostic studies associated with splenic vein thrombosis.

# Treatment

## Medical Therapy
Medical therapy for splenic vein thrombosis include anticoagulation to maintain INR between 2 to 3. The goal of anticoagulation is to prevent extension of the clot and to allow for recanalization. The mainstay of therapy in splenic vein thrombosis with gastric varices is sclerotherapy and gastric banding.

## Surgery
Splenectomy is recommended for all patients with bleeding varices associated with isolated splenic vein thrombosis. Splenectomy eliminates venous collateral out flow and decompresses surrounding varices.

## Primary Prevention
There is no established method for prevention of splenic vein thrombosis.

## Secondary Prevention
There is no established method for prevention of splenic vein thrombosis.