Technical description and feasibility of laparoscopic adrenal contouring using fluorescence imaging

Identification of adrenal glands from the surrounding structures during laparoscopic surgery can be challenging especially in obese individuals. This can increase the chances for hemorrhage and conversion to open surgery. We present the first report of fluorescent infrared visualization of the adrenal glands in a large animal model.

Five adult Yorkshire pigs were utilized for the study, in compliance with the animal study regulations. After an intravenous bolus administration of 3 mL of indocyanine green (ICG), visualization was performed with a xenon/infrared light source and a laparoscope with a charge-coupled filter device. Activation of the device was done with a foot pedal. Images were analyzed using histogram software and the difference of enhancement was statistically analyzed using unpaired two-tailed t test.

The right adrenal glands were visualized in all five animals immediately after administering ICG. Fluorescence facilitated demarcation of adrenal gland tissue from surrounding adipose tissue. Peritoneum and fat was visualized in black color. Adrenal enhancement lasted for 4 h in all cases. The mean value for adrenal fluorescence using histogram count was 71.75 pixels, and for adrenal xenon was 168.87 pixels (p = 0.0002; 95 % CI -130.93 to -0.63). The mean value for fat fluorescence using histogram count was 5.54 pixels and fat xenon was 187.15 pixels (p = 0.0001; 95 % CI -199.39 to -163.82). Although there was no significant difference between adrenal and fat enhancement with xenon light (p = 0.24; 95 % CI -15.53 to 52.09), the difference became significant between adrenal and fat fluorescence (p = 0.0001; 95 % CI 48.51-83.9).

Fluorescence imaging appears to be a feasible and easy method to differentiate adrenal glands from the surrounding tissue in a large animal model. Further studies are necessary to investigate the real application of this method during laparoscopic adrenalectomy in humans.