CT AND MRI OF EXPERIMENTALLY-INDUCED MESENTERIC ISCHEMIA IN A PORCINEMODEL

Objective: Our goal was to assess the value of CT and MRI for the dete ction of bowel wall changes in experimentally induced mesenteric ische mia, Methods: In 18 female pigs, a percutaneous embolization of the su perior mesenteric artery was performed with buthyl-2-cyanoacrylate and Lipiodol (1:1) (experimental group). In six animals, only diagnostic imaging and histologic evaluation were performed (control group). CT w as carried out 3, 6, and 12 h after occlusion. Incremental CT (1 s sca n time, 5 mm slice thickness, 7 mm increment, 120 kV/290 mAs) and spir al CT (slice thickness 5 mm, pitch 1.5, 120 kV/165 mA) were performed pre and post contrast injection (Somatom Plus/Siemens). Serial CT was carried out after intravenous contrast injection (1 ml/kg, 2 ml/s). MR I (Magnetom 1.5 T; Siemens) was performed with T1 (pre and post 0.01 m mol/kg Gd-DTPA; Magnevist; Schering, Germany), T2, and proton density images in axial orientation. Slice thickness was 3 mm and slice gap 1 mm. Additionally, a TI-weighted GE sequence (multislice FLASH 2D) was obtained in dynamic technique (before and 30, 60, and 90 s after contr ast agent injection) with a slice thickness of 5 mm. Biometrical monit oring included blood pressure, heart frequency, blood cell count, elec trolyte status, blood gas analysis, and determination of serum lactate , Image evaluation included morphological analysis and determination o f the enhancement pattern. Histological specimens were obtained and an alyzed according to the Chiu classification. Results: The histologic w orkup of the specimen 3, 6, and 12 h after vascular occlusion revealed an average Chiu state 3, 4, and 5, On CT, the bowel wall had a thickn ess of 4.7 mm on average in the ischemic segments. There was a signifi cant difference from the control group (average 3 mm), Free intraperit oneal fluid and intramural gas were seen after 12 h of ischemia in 80% . In ischemic bowel segments, no mural enhancement was seen. Normal se gments and the bowel of the control animals showed an enhancement of 3 4 PIU on average (SD = 3.1 HU; p < 0.01). In MRI, S/N and C/N differed significantly between experimental and control groups in T1 and proto n density images. In ischemic segments of all phases, the bowel wall d id not show contrast enhancement. Healthy segments and bowel of contro l animals showed a significant enhancement (p < 0.01). Conclusion: Cro ss-sectional imaging has a high sensitivity for delineation of ischemi c bowel wall segments. The enhancement pattern of the bowel wall enabl es detection of location, extent, and cause of a acute arterial mesent eric ischemia with high accuracy in an early phase.