The accuracy of laparoscopic ultrasound in the detection of colorectal cancer liver metastases

Background: The most sensitive and specific method of detecting colorectal cancer hepatic metastases has been shown to be a combination of careful intraoperative palpation and intraoperative ultrasound. Although there has been growing interest in laparoscopic surgical therapy for colorectal cancer, the ability of this technique to adequately evaluate the liver for small metastases has been unknown. This study was undertaken to compare laparoscopic liver ultrasound to the gold standard of open palpation and intraoperative ultrasound in detecting hepatic metastases from colorectal cancer. Methods: A preliminary animal model was first performed in adult pigs. Eighteen liver “lesions” were created with chlorhexidine gluconate under laparoscopic guidance. A blinded surgeon then performed laparoscopic liver ultrasound followed by open ultrasound and palpation, comparing the accuracy of these techniques in detecting the lesions. In a second study, 15 patients undergoing laparotomy for colorectal cancer underwent preliminary laparoscopic liver ultrasound followed by open palpation and intraoperative ultrasound to compare these methods of liver evaluation. Results: Laparoscopic liver ultrasound detected 17 of 18 lesions created in the pig livers, for a sensitivity of 94.4%. There were two false negatives, for a specificity of 77.7%. Laparoscopic liver ultrasound detected 4 of the 5 liver metastases in the human study, for a sensitivity of 80%. There was a single false negative, for a specificity of 90.9%. Several technical difficulties and their solutions are discussed. Conclusions: With several technical modifications guided by our initial experience, we believe laparoscopic liver ultrasound can be an effective way of evaluating the liver for metastases during laparoscopic colorectal resection for cancer.