Radionuclide visualization of acute occlusive and nonocclusive intestinal ischemia

A noninvasive radionuclide technique to visualize ischemic small intestine was evaluated. Vascular ligation of 20-30 cm ileum was done in rabbits. After induction of ischemia, technetium (99mTc) methylene diphosphonate (TMDP) was injected IV at intervals up to 24 hours. Images were recorded 1 and 3 hours after injection of radioisotope and showed preferential (9:1) uptake by ischemic bowel. Positive scans were present in all animals up to 4 hours and in 75% at 10-12 hours, but in none 24 hours after induction of ischemia. Nonocclusive intestinal ischemia was simulated in 4 dogs by infusing norepinephrine into a jejunal mesenteric arterial branch. After 1 hour, an IV bolus of TMDP was injected and images recorded at intervals up to 3 hours. Selective uptake of isotope by the ischemic segment was observed in all animals. Angiography confirmed that isotope uptake was confined to the infused segment. These studies show that occlusive intestinal ischemia can be detected, by radionuclide imaging up to 12 hours, and nonocclusive (low flow) ischemia for at least 4 hours, after onset.