LIMITATIONS OF ENDORECTAL ULTRASONOGRAPHY - WHAT DOES A LOW ECHOIC LESION MORE THAN 5 MM IN SIZE CORRESPOND TO HISTOLOGICALLY

PURPOSE: The accuracy of diagnosis of metastatic lymph nodes for recta l carcinoma has not improved. A low echoic lesion more than 5 mm in si ze detected by endorectal ultrasonography is preoperatively assessed a s a metastatic lymph node. What does a low echoic lesion more than 5 m m in size correspond to histologically? METHODS: Forty-seven patients with lower rectal carcinoma (Term I, 1986-1990) and 48 patients with l ower rectal carcinoma (Term II, 1991-1995) undergoing endorectal ultra sonography were reviewed. Surgically resected rectal specimens from 40 patients with rectal carcinoma underwent ultrasonography. Low echoic lesions more than 5 mm in size were taken from resected specimens and were stained with hematoxylin, followed by histologic examination. RES ULTS: The accuracy of diagnosis of metastatic lymph nodes of Term II w as not higher than that of Term I. Twenty-five low echoic lesions were detected by ultrasonography using 40 resected specimens. Seventeen of these 25 lesions (68 percent) were histologically confirmed to be met astatic lymph nodes. One of 25 (4 percent) was found to be lymphadenit is with no metastasis. Among the 25 lesions, 5 (20 percent) were histo logically confirmed to be tumor deposits, 2 (8 percent) fatty tissue, and 22 (88 percent) carcinoma. CONCLUSIONS: Low echoic lesions were hi stologically confirmed to be tumor deposits (20 percent) and metastati c lymph nodes (68 percent). Although these data show deficiencies and limitations of the accuracy of endorectal ultrasonography, they compar e favorably with other series, and no other current technology can sho w similar accuracy.