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Acute Mesenteric Ischemia Induced by Ligation of Porcine Superior Mesenteric Vein

Posted Aug 31, 2010 Updated Apr 7, 2023
By Zuo Hua Tang MD , Jin Wei Qiang MD PhD , Xiao Yuan Feng MD PhD , Ruo Kun Li MD , Rong Xun Sun MD , Xuan Guang Ye MD
7 min read

Rationale and Objectives

To evaluate multidetector computed tomography (MDCT) for detecting the early changes and dynamic evolution of acute mesenteric ischemia (AMI) induced by the ligation of superior mesenteric vein (SMV) in an experimental porcine model.

Materials and Methods

Twelve pigs were randomly assigned to three experimental groups, and one control group with three pigs in each group. After laparotomy, the SMV was separated and ligated in nine pigs and separated without ligation in three controls. MDCT pre- and postcontrast with arterial, venous, and delayed phase scans, and CT angiography reconstructions of mesenteric vessels were carried out at preoperation, 6 hours, 12 hours, and 18 hours after ligation. The findings of mesenteric vessels, bowel, abdominal cavity at pre- and postoperation, and dynamic evolution were correlated with pathology.

Results

AMI-induced pathological changes were identified in all nine experimental pigs. MDCT angiography clearly delineated main trunk of the SMV, peripheral major and minor tributaries up to brushy vasa recta, and the location and shape of ligations. The early ischemic findings were bowel wall thickening, mesenteric edema, ascites, and pronounced bowel enhancement. Superior mesenteric artery and its major branches appeared spasm with poor filling and delayed and prolonged visualization. SMV and its tributaries were poorly delineated with delayed opacification. We also saw thinning of bowel wall, dilatating bowel with fluid, aggravating mesenteric edema and ascites, and poor enhanced bowel over time.

Conclusion

MDCT detects early changes of mesenteric ischemia and its evolution after ligation of porcine SMV, and may find application in early diagnosis of human venous occlusive AMI.

Mesenteric venous thrombosis (MVT) remains a lethal disease. It usually results in acute mesenteric ischemia (AMI) and even necrosis if not promptly treated. The 30-day mortality is 20%–27% . Because of variations in clinical manifestations, courses, and prognosis from different etiology of MVT, it is hard to diagnose acute MVT at an early stage. Improvements in noninvasive imaging techniques, especially multidetector computed tomography (MDCT), may lead to a more favorable outcome of acute MVT . Identifying patients earlier in their clinical courses can not only avoid intestinal necrosis and unnecessary surgery, but also prompt nonoperative management such as interventional therapy, and hence reduce mortality. According to Zhang et al , mortality rate reached up to 39% in patients with acute MVT who underwent surgical therapy, whereas nonoperative management or interventional therapy markedly reduced hospital mortality.

It was shown that sensitivity and specificity of MDCT for MVT were both higher than 90% when MVT occurs in main trunk of superior mesenteric vein (SMV) or portal vein, whereas characteristic changes of AMI usually appeared at a late stage. The value of MDCT remains uncertain in the identification of the early AMI, or in MVT involving predominantly the small mesenteric veins. A retrospective study by Kumar et al suggested that 44% of MVT predominantly involved the small mesenteric veins, which was more difficult to diagnose early, more likely to develop bowel necrosis, and more frequently required surgery.

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Materials and methods

Animal Preparation

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Imaging Protocols

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CT Data Analysis

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Pathological Analysis

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Statistical Analysis

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Results

CTA Manifestations of Normal SMV

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Figure 1, Thin slab maximum intensity projection image shows that the superior mesenteric vein (SMV) was converged by jejunal veins (JV), ileal veins (IV), and ileocolic vein (ICV), which is formed by the colic vein (CV) and IV. The SMV joins the splenic vein (SV) to form the portal vein (PV). The JV are located in the right upper quadrant. IV are in the lower quadrants and continue to SMV. Ileocolic vein is in the left abdomen and transversally joined SMV from the left, and has two tributaries draining the colon at left abdomen and the distal ileum at the left lower quadrant. More distal tributaries appear brushy along the main trunk.

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CTA Findings of Mesenteric Ischemia

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Figure 2, Thin slab maximum intensity projection (TSMIP) images of arterial phase (a) and venous phase (b) before operation clearly show fully filled main trunk and branches of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV). TSMIP images of arterial phase (c) and venous phase (d) at 6 hours after operation show spasm of SMA and its major branches with markedly shrunk caliber, poor filling, and fewer branches. SMV and its tributaries demonstrate smaller caliber and poor and delayed opacification. The sites of ligation appear as a nonopacification area with the shape of slim waist ( arrows ). Distal to the ligation, the veins still opacify with a larger inflexible caliber.

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Abnormal CT Findings of Bowel and Abdominal Cavity

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Figure 3, Coronal multiplanar reformation images at preoperation (a) , 6 hours (b) , 12 hours (c) , and 18 hours (d) after the ligation show dynamic changes with dilatating bowels with fluid and aggravating ascites.

Table 1

Abnormal Computed Tomography Findings of Bowel and Abdominal Cavity and Dynamic Evolution

Abnormal Computed Tomography Findings 6 Hours

( n = 9) 12 Hours

( n = 6) 18 Hours

( n = 3) Controls

( n = 3) Thickening of bowel wall 9 (100%) ∗ 5 (83%) ∗ 1 (33%) 0 Thinning of bowel wall 0 (0) 1 (17%) 2 (67%) 0 Bowel dilatation with fluid 1 (11%) 2 (33.3%) 3 (100%) 0 Mesenteric edema 9 (100%) ∗ 6 (100%) ∗ 3 (100%) 0 Ascites 8 (89%) ∗ 6 (100%) ∗ 3 (100%) 0 Increased enhancement of bowel wall 9 (100%) ∗ 0 (0) 0 (0) 0 Reduced enhancement of bowel wall 0 (0) 6 (100%) ∗ 3 (100%) 0

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Pathologic Findings

Gross observation

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Histological findings

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Figure 4, Normal bowel wall shows intact mucosal layer and submucosal layer (a) . At 6 hours after ligation of superior mesenteric vein, congestion and edema are seen in the submucosal layer with intact mucosal layer (b) . At 12 hours, the entire bowel wall shows congestion and edema with focal mucosal necrosis. More striking venule dilatation and infiltration of inflammatory cells appear in submucosal layer (c, d) . At 18 hours, there are diffuse mucosal necrosis and ulcerations in mucosa, interruption and dissolving of muscle fiber, and fibrous exudation in the serosa (e, f) .

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Discussion

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Academic Radiology, Volume 17, Issue 9
Journals General Radiology
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