LIMITATIONS AND PITFALLS OF TRANSRECTAL ULTRASONOGRAPHY FOR STAGING OF RECTAL-CANCER

PURPOSE: This study was designed to evaluate the accuracy of preoperat ive staging by transrectal ultrasonography (TRUS) and to clarify the l imitations and pitfalls of TRUS by clinicopathologic analysis for stag ing errors. MATERIALS AND METHODS: Results of TRUS for 164 consecutive patients with rectal cancer were compared prospectively with histopat hologic findings according to the newest TNM classification. Clinicopa thologic factors that may influence staging errors were analyzed by re viewing both resected spec imens and hard copies of TRUS. RESULTS: The re were 13 patients histopathologically staged as pTis, 21 as pT1, 34 as pT2, 84 as pT3, 12 as pT4, 73 as pN0, and 91 as pN1-3. Of these, 85 , 86, 56, 93, 75, 74, and 77 percent, respectively, were correctly sta ged by TRUS. Excluding 12 cases with incomplete examinations because o f annular constricting tumors, overstaging of tumor invasion depth was mostly caused by tumor invasion close to the deeper uninvolved layer, inflammatory cell aggregation, desmoplastic change, and hypervascular ity around the tumor, mimicking tumor invasion on TRUS. The understagi ng was mostly the result of microscopic invasion beyond the estimated layers and difficulties in examination because of the tumor location b eing close to the anal canal or on the Houston's valves or the tumor s hapes being polypoid or bulky and fungating. Overstaging in lymph node status was caused by reactive lymph node swelling and understaging by the presence of only small involved node and metastasis in the extram esorectal nodes. CONCLUSIONS: An awareness of the Limitations and pitf alls of TRUS, as demonstrated by the present study, should improve sta ging accuracy and contribute to optimum clinical decision-making.