New method of sentinel node detection using a combination of contrast-enhanced ultrasound and dye guidance: an animal study.

Abstract

To determine whether a combination of contrast-enhanced ultrasound-guided methods and dye-guided methods can identify sentinel lymph nodes in animals. Seven pigs were put under general anesthesia and injected subcutaneously in the neck: three with 2 ml saline and four with 2 ml fluid comprising 0.4 ml 5% patent blue violet solution and 1.6 ml of hydroxyethylated starch (Salinhes) solution (PB + HS). The regional lymph nodes were observed by ultrasound; blue-stained regional lymph nodes found after the skin was cut were situated as ultrasound had shown they would be. The regional lymph nodes of the pigs given saline were unchanged, but in the pigs receiving PB + HS, the echo level in the lymph nodes nearest the injection site was altered, producing a clear contrast with the surrounding tissues. The area of the relevant regional lymph node in each PB + HS-injected pig increased significantly (t-test, P < 0.01; from 25.7, 39.6, 9.36, 70.2 mm(2), and mean, 36.2 mm(2); to 50.7, 65.5, 21.1, 98.3 mm(2), and mean, 58.9 mm(2), respectively). These enlarged regional lymph nodes were easily found by contrast-enhanced ultrasonography. When excised under ultrasound guidance, all were stained blue, indicating that they were sentinel lymph nodes. These results suggest that this combination of contrast-enhanced ultrasound-guided and dye-guided methods warrants use as a quick, simple procedure for detecting sentinel lymph nodes.