OBJECTIVETo evaluate the accuracy of transrectal ultrasonography (TRUS) in the assessment of the invasion depth of rectal cancer, and analyze the value of TRUS in diagnosis of early rectal cancer.

METHODSTRUS was performed preoperatively in 163 patients with rectal cancer, and the results was compared with the postoperative pathological findings according to TNM staging. The early rectal cancer was diagnosed if the lesion was limited to mucosa and submucosa. The tumor located in mucosa was defined as mucosal cancer, while as submucosal cancer when the tumor invading into submucosa. Sixteen cases were confirmed as early cancer by pathology after the operation. No patients received chemotherapy and radiotherapy before operation.

RESULTSThe sensitivity of TRUS in the staging of the early rectal cancer was 87.5% (14/16), specificity was 98.6% (145/147), and the positive predictive value was 87.5% (14/16). The sensitivity of TRUS in predicting mucosal and submucosal cancer was 85.7% (6/7) and 66.7% (6/9), respectively. Sixteen patients with early rectal cancer were examined before and after filling rectum with water. After filling rectum, all tumors were visualized clearly, while 14 tumors were correctly diagnosed as early rectal cancer. Before filling rectum, only 6 tumors were visualized clearly, and 3 tumors were staged correctly. The ultrasonographic appearance of early rectal cancer manifested in two kinds: protruded and ulcerative, and most were protruded (81.6%).

CONCLUSIONSTRUS is a valuable imaging examination for diagnosis of early rectal cancer preoperatively. Visualization rate and diagnostic accuracy of early rectal cancer are improved dramatically after filling rectum with water.