Overview of mesenteric vein thrombosis
Mesenteric vein thrombosis refers to thrombosis of the mesenteric veins caused by hemodynamic changes or hypercoagulability of the blood. It accounts for 5% to 15% of all ischemic diseases of the mesenteric vasculature and usually involves the superior mesenteric vein, while the inferior mesenteric vein is rarely involved. It can be categorized as primary or secondary. Those with a clear etiology are called secondary, while those with an unknown etiology are called primary or idiopathic. The diagnosis is often delayed because of the insidious clinical presentation, and in most cases the diagnosis is made only during open abdominal exploration.
Etiology
The most common cause is hypercoagulability due to hereditary or acquired conditions such as tumors, abdominal inflammation, postoperative, cirrhosis and portal hypertension. The use of oral contraceptives accounts for 9% to 18% of patients with superior mesenteric vein embolism in young women.
Symptoms
1. Abdominal pain
In most cases, abdominal discomfort is the first prodromal symptom, followed by abdominal pain, which gradually intensifies, mostly paroxysmal colic, and only a few cases start with severe abdominal pain. The extent of abdominal pain varies according to the severity of the lesion. In mild cases, the pain is limited, while in severe cases, it can be generalized abdominal pain. Most patients have a long history of abdominal pain before admission to the hospital, ranging from a few days to several weeks.
2. Nausea and vomiting
Nausea and vomiting may occur in about half of the patients.
3. Diarrhea or bloody stools
A few patients may have diarrhea or thin bloody stools.
4. Fever
A few patients may have fever, but usually not more than 38℃. If there is high fever, it suggests complicated infection.
5. Physical signs
Abdominal pressure pain, rebound pain, but the degree is mild and muscle tension is not obvious. In a few patients, dilated and thickened intestinal collaterals can be palpated. Bowel sounds are normal in the early stage and often weaken or disappear in the late stage. Abdominal puncture is helpful in the diagnosis of the disease when a reddish bloody fluid is withdrawn.
Tests
Laboratory tests are usually not helpful in the diagnosis of superior mesenteric vein thrombosis. Metabolic acidosis and elevated serum lactate levels can be used to determine the presence of intestinal necrosis, but are often a sign of advanced disease.
1. Abdominal radiographs
Only 5% of patients show specific signs of intestinal ischemia, and the presence of a finger-pressure sign in the intestinal lumen suggests ischemia of the intestinal mucosa. Emphysema of the intestinal wall or free gas in the portal vein is characteristic of intestinal infarcts due to mesenteric vein thrombosis.
2. Color Doppler ultrasound of abdomen
It can detect mesenteric vein thrombosis, but electronic computed tomography (CT) should be used in cases where mesenteric vein thrombosis is suspected.
3. CT
CT can lead to a diagnosis in 90% of patients, but is less accurate in the diagnosis of small thrombi in the early portal vein.
4. Selective mesenteric angiography: can show thrombi located in large veins or delayed visualization of superior mesenteric veins.
5. Magnetic resonance imaging
Magnetic resonance imaging has high sensitivity and specificity in the diagnosis of superior mesenteric vein thrombosis, but its examination process is more complicated and its popularity is poor.
6. Other
Patients with mesenteric vein thrombosis can have plasma-blood peritoneal effusion, in which case diagnostic laparotomy may be helpful. Pneumoperitoneum manipulation during laparoscopy may increase intra-abdominal pressure and decrease mesenteric blood flow and should be avoided. Colonoscopy and gastroduodenoscopy are of limited value because the colon and duodenum are rarely involved. Endoscopic ultrasonography can detect mesenteric vein thrombosis, but is best used in patients without acute symptoms because of the intestinal dilatation caused during the examination. In cases of superior mesenteric vein thrombosis, CT angiography (CTA) is a better test, not only to visualize the mesenteric vessels and to determine the extent of the involved bowel, but also to rule out other diseases that cause abdominal pain. Mesenteric angiography, on the other hand, should be used in patients with a suspected tendency to thrombosis, in which case the thrombus is often located in smaller vessels of the mesenteric venous system.
Diagnosis
1. Abdominal pain is subacute and progressively worse, accompanied by signs of gastrointestinal bleeding, such as bloody stools.
2. The degree of abdominal pain and abdominal signs can be inconsistent, abdominal pain symptoms are heavy and signs are light is an important feature of the disease.
3. Peritonitis is accompanied by bloody exudate in the abdominal cavity.
Treatment
1. Surgical treatment
The treatment of mesenteric vein thrombosis includes anticoagulation and anticoagulation combined with surgery. For patients with acute or subacute mesenteric ischemia, heparin treatment should be started as soon as the diagnosis is made. Not all patients with superior mesenteric vein thrombosis require surgical exploration, but those with clear signs of peritonitis must be operated on urgently. Anticoagulation should be initiated intraoperatively if the diagnosis of mesenteric vein thrombosis is established. Avoiding resection of too much potentially viable bowel is preferable to a secondary exploration after 24 hours. Secondary exploration is particularly indicated in patients with extensive involvement of the bowel and some mesenteric blood flow. In some cases, the option of performing a conservative bowel resection without a one-stage anastomosis of the bowel and dragging the severed end out of the abdominal wall stoma, which serves as a window into the viability of the bowel, is also available, and may spare some less well off patients from a secondary exploration. In rare cases, thrombectomy can be performed if the thrombus is short-lived and confined to the superior mesenteric vein. Thrombectomy should not be performed for more extensive thrombi. Arterial spasm is a common condition, and removal of potentially revitalized ischemic bowel can be avoided by a combination of intra-arterial opioid infusion, anticoagulation, and secondary exploration.
2. Medication
In the absence of intestinal necrosis, mesenteric vein thrombosis can be treated medically without surgery. In patients without peritonitis or perforation, intravenous antibiotic therapy is not required. However, heparin anticoagulation given immediately in the early stages of the disease can significantly improve patient survival and reduce recurrence rates, even if applied during surgery. Systemic heparin therapy can be initiated by giving heparin intravenously, followed by a continuous infusion to keep the activated partial thromboplastin time at more than two times normal. Even in the presence of GI bleeding, anticoagulation may be given if the risk of intestinal necrosis is greater than the risk of GI bleeding.
3. Other treatments
Other supportive therapies include gastrointestinal decompression, fluid resuscitation, and fasting. Oral anticoagulants may be given after it is clear that there is no further ischemia in the bowel. Despite the possibility of esophageal varices and bleeding, the benefits of long-term anticoagulation still outweigh the risk of bleeding. In patients without new thrombosis, anticoagulation should be maintained for 6 months to 1 year. Catheter placement into the portal vein and injection of urokinase or tissue fibrinolytic activator for direct thrombolysis has only been reported in a few attempts. The high risk of bleeding and the low success rate of thrombolytic therapy due to late patient presentation make this method successful in only a few cases. If the thrombus is located in a larger vessel, the prognosis is poor, and the expected benefits of performing direct thrombolysis outweigh the risk of bleeding, direct thrombolysis by cannulation may be considered.