Perirectal lymph nodes in rectal cancer: in vitro correlation of sonographic parameters and histopathologic findings

Preoperative staging of lymph nodes in patients with rectal cancer is essential for selecting the most appropriate therapy. To determine the discriminating value of all ultrasound parameters described in the literature, the authors obtained high-frequency sonograms of 43 lymph nodes in 21 resected rectal specimens, thereby simulating the in vivo situation. Univariate analysis revealed that inhomogeneity (P less than .0005), short axis diameter (P less than .005), and hilar reflection (P less than .01) were helpful in differentiating between metastatically involved and noninvolved lymph nodes. A prognostic trend was seen for long-axis diameter (P = .05), roundness index (P = .09), and echogenicity (P = .05). With stepwise logistic regression analysis, inhomogeneity and hilar reflection were selected as being independently discriminative. Inhomogeneity is a parameter with a high specificity; hilar reflection is particularly sensitive. No clear differentiation could be made, however, in a sizable proportion of lymph nodes (60%). The prospective use of especially these significant parameters in vivo is recommended to determine their ultimate value in preoperative staging.