The assessment of wall invasion of rectal carcinoma: correlation of endoluminal ultrasonographic and pathologic findings

Abstract

To evaluate the accuracy of endoluminal ultrasonography (ELUS) in the preoperative assessment of wall invasion of rectal carcinoma and analyze its influencing factors. ELUS was performed preoperatively in 117 patients with rectal carcinoma, in which no preoperative treatment was given. The results of ELUS were correlated with operative and pathologic findings according to the TNM classification. We observed the following factors and analyzed their impact on the accuracy of ELUS: tumor location, the depth of the tumor invasion, and the inflammatory cell infiltration and fibrosis peritumor. The overall accuracy of ELUS in T stage was 76.9% (90/117). The sensitivity of ELUS for pT(1), pT(2), pT(3) and pT(4) carcinoma was 87.5% (7/8), 51.7% (15/29), 85.7% (60/70), 80% (8/10), respectively. Misdiagnosis occurred in 27 cases, of which 14 cases were overstaged and 13 cases were understaged. The sensitivity for pT(2) carcinoma was the lowest; 14 cases were misdiagnosed, of them 13 cases were overstaged. Overstaging with ELUS for pT(2) carcinoma occurred mainly in these cases in which inflammatory cell infiltration, fibrosis or tumor involved more than one-third of muscularis propria. 13 cases were understaged, of which tumors in 7 cases were located in superior segment of rectum and 4 cases with obviously rectal stenosis. When tumor was located in middle or lower segment of rectum, misdiagnostic rate was 18.5% (17/92); while tumor was located in superior segment of rectum, misdiagnostic rate was 40% (10/25), and differences were statistically significant between two groups in misdiagnostic rate (P = 0.024). Although ELUS in the preoperative assessment of wall invasion of rectal carcinoma is useful, it is difficult to avoid overstaging and understaging of ELUS. The overstaging is an important unfavourable factor in assessing the invasion depth of pT(2) carcinoma with ELUS, and the depth of tumor invasion muscularis propria, and the depth of inflammatory cell infiltration and fibrosis might be responsible for overstaging. Obviously rectal stenosis and tumor being located in the superior segment of rectum might cause understaging.