Small Animal Surgery Resident Ontario Veterinary College, University of Guelph Guelph, Ontario, Canada
Near-Infrared Fluorescence Cholangiography in Dogs: A Pilot Study. Larose PC, Brisson B, Sanchez-Lazaro A, Monteith G, Singh A, Zhang M. University of Guelph, Ontario Veterinary College, Guelph, ON, Canada.
The purpose of this study was to determine the effect of Indocyanine green (ICG) dose and timing of administration on near-infrared fluorescence (NIRF) imaging of the normal canine biliary tree. Eight healthy research beagles were randomized to receive two of four intravenous ICG dose (L: 0.05 mg/kg or H: 0.25 mg/kg) / time (0 and 3 h prior to NIRF) combinations. NIRF images were collected every 10 minutes for 120 minutes. Target (cystic duct)-to-background (liver) ratios were calculated for all timepoints and compared. ICG cholangiography was successful in all dogs. The contrast ratio was above 1 in the L0 group by time 20 minutes and reached its peak at 100 minutes. In the H0 group, the ratio was above 1 by 60 minutes and reached its peak at 90 minutes. Contrast ratios above 2 (fluorescence twice as bright in the cystic duct compared to liver) were maintained from 180 to 300 minutes for L3 and H3 and was achieved after 80 minutes for L0. Low-dose ICG provided better ratios early after injection (time 0–120 minutes) compared to high dose which remained highly concentrated in the liver tissue after injection and resulted in lower target-to-background ratios. Though both doses provided excellent visualization of the biliary tree at three hours post injection, low dose ICG provided better ratios from three to five hours post injection. Based on these results, 0.05 mg/kg of ICG administered at anesthetic induction or as early as three hours prior to laparoscopic surgery should yield optimal fluorescence images. Evaluation in a clinical population undergoing cholecystectomy is necessary and is underway.