A37-year old man presented to our Accident and Emergency department with severe diffuse
abdominal pain of 2 days duration. Clinical examination was negative except for mild abdominal distension. Radiograph of abdomen did not reveal any abnormality. Patient then underwent CT abdomen, images of which are shown. What is the diagnosis?
[TAG:2]Superior Mesenteric Vein Thrombosis with Segmental Ischemia of Small Bowel.[/TAG:2]
CECT abdomen shows dilated Superior mesenteric vein with a filling defect [Figure - 1],[Figure - 3], consistent with intraluminal thrombus. A lop of small bowel shows thicknened wall and poor enhancement [Figure - 2], representing bowel ischemia.
The differential diagnosis of thickened small-bowel wall in CT includes neoplasma, inflammatory conditions, radiation enteritis, enteric infections, ischemia, and submucosal hemorrhage. The presence of a persistent filling defect in the superior mesenteric vein as in our patient indicates that the mural thickening is due to ischaemia from superior mesenteric venous thrombosis.
Mesenteric vein thrombosis (MVT) accounts for 5-10% of cases of acute mesenteric ischemia (1) and can lead to bowel infarction and peritonitis It has a 30-day mortality of 13-50% (2). Diagnosis of MVT is often delayed due to the rarity of the condition and non-specific symptoms. Patient with acute MVT may present with severe abdominal pain described as out of proportion to the physical findings, nausea, vomiting, constipation or diarrhea (2). Physical signs depend on the severity and stage of intestinal injury. Signs of peritonitis develop only late. Laboratory abnormalities include leucocytosis, neutrophilia, elevated serum lactate, and hyperamylasemia. Metabolic acidosis and hypoxia suggest severe intestinal insult (3). Occult blood will be detectable in the stool in nearly 50 percent of patients (4). When no predisposing cause is detected for thrombus formation, mesenteric venous thrombosis is termed primary. Secondary MVT account for about 75% cases and is commonly due to prothrombotic states due to heritable or acquired disorders of coagulation or cancer. Other causes for MVT include intrabdominal inflammations, postoperative stage, oral contraceptive use, cirrhosis, and portal hypertension (5).
plain radiographs of abdomen in patients with MVT are usually normal or demonstrate nonspecific abnormalities, such as an ileus. Focal mural thickening due to submucosal thickening (thumb printing), pneumatosis intestinalis and portal venous air may be seen in late stage disease with bowel infarction (5). CT is the diagnostic test of choice for mesenteric venous thrombosis (6) with sensitivity rate at least 90% (2). CT demonstrates the thrombus as a persistent central low-density area surrounded by an hyper dense rim which is due to partial luminal patency. The ischemic segment of bowel shows mural thickening and may be hypo dense, hyper enhancing or with alternating areas of hyper and hypo dense areas, referred to as the target sign (7). Hypoattenuation of a thickened bowel wall, representing bowel wall edema is more typical of acute bowel ischemia caused by mesenteric venous occlusions (1). The mesentery shows fat stranding and fluid. There may be ascites. In advanced ischemia, there may be pneumatosis intestinalis and air in mesentero-portal veins.
Doppler ultrasound is limited in the evaluation of MVT due to its operator dependency and inability to depict vascular anatomy accurately in the presence of overlying bowel gas (5). SMVT can also be diagnosed with direct or indirect portography. Though invasive, these techniques facilitate endovascular therapeutic maneuvers such as transcatheter delivery of vasodilators or thrombolytic agents (5) MRI offers the advantage of safer contrast agents and lack of ionizing radiation. According to Bradbury et al, helical CT angiography and three-dimensional contrast enhanced MR angiography should be considered the primary diagnostic modalities for patients with a high clinical suspicion of mesenteric ischemia (5).
Patients with superior mesenteric veinthrombosis are treated medically with intravenous heparin unless there are features of bowel infarction. Radiologically, the triad of low attenuation in the superior mesenteric vein, thickening of the small bowel wall, and the presence of periotoneal fluid suggests that laprotomy should be performed, as bowel infarction is likely (5). Minimal bowel resection with liberal use of second-look laparotomy after 24 hours is advocated (2). Diagnostic laproscopy has been found to be useful to assess the status of bowel and helps avoid unnecessary laprotomy (8).
Our patient underwent laparoscopic resection of the ischemic segment of bowel and was anticoagulated with intravenous heparin for 5 days. He was discharged 7 days after surgery on Warfarin. Investigations did not reveal any cause for venous thrombosis, thus making this a case of primary mesenteric venous thrombosis.