Early diagnosis of experimental necrotizing enterocolitis using proton nuclear magnetic resonance

The purpose of this study was (1) to confirm an experimental model of aminophylline-induced necrotizing enterocolitis (NEC); and (2) to determine whether nuclear magnetic resonance (NMR) imaging, based upon proton relaxation values (T1, T2), could detect NEC during its early pathogenesis. Sixty male weanling Lewis rats (avg wt = 75 g) were randomly assigned to one of three experimental groups: (A) superior mesenteric artery (SMA) occlusion (1 min) + aminophylline treatment (40 mg/kg); (B) SMA occlusion; and (C) sham midline laparotomy (control). All surviving animals were sacrificed at 48 hr postoperation and a specimen of ileum was removed for light microscopy (LM), electron microscopy (EM), and NMR analysis. Percentage water content was determined for representative specimens. Mortality occurred only in experimental group A animals (18.2%; P less than 0.05), who had received aminophylline. Microscopy of ileum from sacrificed animals of this group showed changes ranging from mild cellular disruption to severe hemorrhagic necrosis. Early ultrastructural changes consistent with NEC were detectable with EM before LM. Proton relaxation results obtained with NMR showed significant prolongation of T1 (252.5 +/- 4.4 msecs; P less than 0.001) and T2 (69.3 +/- 1.4 msecs; P less than 0.025) during the first stages of NEC. NMR may indeed enable early, safe diagnostic imaging of NEC in infants receiving aminophylline, or those who are otherwise at increased risk for development of this disease.