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Diagnosis of persistent intestinal ischemia in the rabbit using proton magnetic resonance imaging
A Park1, R A Towner, J C Langer
1Department of Surgery, McMaster University, Hamilton, Ontario, Canada.
Abstract:
Noninvasive diagnosis of persistent intestinal ischemia remains an elusive goal. Magnetic resonance imaging (MRI) recognizes changes in tissue water content, and several authors have demonstrated increased intensity within 6 hours of intestinal ischemia. To simulate the clinical situation more closely, we studied the efficacy of MRI in differentiating ischemic from viable segments of bowel 24 hours after injury in a rabbit model. A segment of distal ileum was rendered ischemic by vascular isolation and ligation. Controls underwent sham operation without vascular ligation. After 24 hours, multislice transverse scans were done using both T1 and T2 weighting. Image intensity was calculated from the isolated loop (absolute intensity), and paraspinal muscle intensity was used as an internal standard to calculate relative intensity (isolated bowel/paraspinal muscle). Animals were killed and bowel necrosis was confirmed histologically. Both absolute and relative intensity were significantly higher in animals undergoing persistent intestinal ischemia. This was true using both T1 and T2 weighting. In a further group of rabbits using the same model, intensity was calculated both before and after intravenous gadolinium. No significant difference was seen between sham and ischemic animals. Our data show that (1) MRI can differentiate ischemic from viable bowel 24 hours after ischemic injury, and (2) the use of intravenous contrast does not improve accuracy. We conclude that MRI may represent a useful noninvasive technique for the diagnosis of persistent intestinal ischemia and that clinical studies should be initiated.
Insights
Magnetic resonance imaging (MRI) can differentiate persistent intestinal ischemia from viable bowel 24 hours after injury. This noninvasive technique shows promise for diagnosing intestinal ischemia, with contrast agents not improving accuracy.
Area of Science:
- Medical Imaging
- Gastroenterology
- Surgical Research
Background:
- Noninvasive diagnosis of persistent intestinal ischemia is challenging.
- Magnetic resonance imaging (MRI) detects changes in tissue water content.
- Previous studies showed increased MRI intensity within 6 hours of intestinal ischemia.
Purpose of the Study:
- To evaluate MRI's efficacy in distinguishing ischemic from viable bowel 24 hours post-injury.
- To simulate a more clinically relevant timeframe for diagnosing intestinal ischemia.
Main Methods:
- A rabbit model of persistent intestinal ischemia was created via vascular ligation of the distal ileum.
- Multislice T1- and T2-weighted MRI scans were performed 24 hours after injury.
- Image intensity (absolute and relative to paraspinal muscle) was quantified; histological confirmation of necrosis was performed.
Main Results:
- Both absolute and relative MRI intensity were significantly higher in ischemic bowel segments compared to controls.
- These findings were consistent for both T1 and T2 weighting.
- Intravenous gadolinium contrast administration did not enhance the differentiation between ischemic and viable bowel.
Conclusions:
- MRI can effectively differentiate ischemic from viable bowel 24 hours after ischemic injury in a rabbit model.
- Intravenous contrast agents do not improve MRI accuracy for this condition.
- MRI shows potential as a noninvasive diagnostic tool for persistent intestinal ischemia, warranting clinical investigation.