ENDOSCOPIC ULTRASONOGRAPHY IN THE DIAGNOSIS OF COLORECTAL-CANCER INVASION

Endoscopic ultrasonography was pre-operatively performed in 164 patien ts with colorectal cancer, and the resected specimens confirmed to be cancerous histologically. Normal colorectal wall was visualized by end oscopic ultrasonography as a five-layered structure. The first, third, and fifth layers were hyperechoic, and the second and fourth layers w ere hypoechoic. The first and second layers comprised the mucosa, the third layer the submucosa, the fourth layer the muscularis propria, an d the fifth layer the subserosa and serosa (adventitia). By this techn ique, cancer of the colon appeared as a hypoechoic mass with an interm ediate echo level between the third hyperechoic and fourth hypoechoic layers. Endoscopic ultrasonographic determination of the depth of tumo r invasion was based on abnormal changes of these layered structures a nd adjacent organs. Overall, the accuracy rate of endoscopic ultrasono graphy in the diagnosis of the depth of colorectal cancer was 83%. A h ypoechoic round mass adjacent to the cancer was interpreted as a metas tatic lymph node. The sensitivity and specificity of endoscopic ultras onography in the diagnosis of lymph node metastasis were 68% and 70%, respectively. The overall accuracy rate of tumor staging by endoscopic ultrasonography according to Dukes' classification was 62%. Endoscopi c ultrasonography is a valuable tool in the management of colorectal c ancer. It has a high accuracy rate in determining the depth of tumor i nvasion. The pre-operative information obtained with this tool may inf luence the choice of therapy.