The accuracy of intraoperative ultrasonography in diagnosing liver metastasis was evaluated at the time of surgery and at follow-up in 189 patients with colorectal cancers. Evaluation at the time of operation revealed that the sensitivity of intraoperative ultrasonography (93.3%) was significantly (p<0.0001) higher than that of preoperative ultrasonography (41.3%), conventional computed tomography (47.1%), and surgical exploration (66.3%). Twenty-two of 104 metastatic liver tumors were detected solely by intraoperative ultrasonography in 18 patients (9.5% of total patients). These 22 tumors were small in size (4×4 mm to 15×18 mm) and nonpalpable during operation. During the postoperative follow-up period of 18 months or more (mean 35.6 months, median 37.1 months) after colorectal surgery, liver metastases that were unrecognized during surgery appeared in 13 (6.9%) patients. Re-evaluation based on these follow-up results indicated that the sensitivity of intraoperative ultrasonography decreased to 82.3%, which was still significantly (p< 0.0005) better than that of other methods. Intraoperatiye ultrasonography was capable of identifying 18 of 31 (58.1%) patients in whom liver metastases were otherwise unrecognized at the time of operation. Intraoperative ultrasonography is more accurate in diagnosing liver metastasis than traditional screening methods, and may have a beneficial impact on the management of colorectal cancer.
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