Depiction and Local Staging of Rectal Tumors: Comparison of Transrectal US before and after Water Instillation

PURPOSE: To determine whether transrectal ultrasonography (US) with intrarectal water instillation can improve the depiction and accuracy of US in local staging of rectal tumors. MATERIALS AND METHODS: Between October 1999 and February 2002, 63 patients (mean age, 56 years; age range, 23-91 years) with 63 rectal tumors were evaluated with transrectal US before and after intrarectal water instillation. Transrectal US examinations were performed with a 7-10-MHz radial transducer. Immediately after the first transrectal US examination, the rectal lumen was filled with 50-150 mL of degassed water, and a second US examination was performed. All patients underwent surgery within 1 month after transrectal US. Depiction of the tumor was compared between the two methods. The McNemar test was used to compare the accuracy between the two techniques in local staging of the tumor by using pathologic findings in the resected specimen as the standard. RESULTS: The tumors ranged from 0.5 to 8.0 cm (mean, 2.8 cm) as measured at pathologic evaluation. All 63 tumors were clearly depicted at transrectal US after water instillation, while only 42 (67%) of the tumors were depicted at transrectal US before water instillation. In the 42 tumors clearly depicted at transrectal US examinations both before and after water instillation, the accuracy of transrectal US in local tumor staging was significantly higher after water instillation (85.7% [36 of 42]) than before water instillation (57.1% [24 of 42]; P < .001). CONCLUSION: Water instillation during transrectal US examination of rectal tumors improves the depiction and local staging of the tumors.