Comparison of computed tomography and magnetic resonance imaging in the discrimination of intraperitoneal and extraperitoneal rectal cancer: initial experience.

OBJECTIVES: To compare computed tomography (CT) and magnetic resonance imaging (MRI) in evaluation of intraperitoneal/extraperitoneal location of rectal cancers. METHODS AND MATERIALS: We assessed the identification of the anterior peritoneal reflection (APR) and the distance from the inferior edge of tumors to the anal verge and from the APR to the anal verge. RESULTS: Distances obtained with CT and MRI showed a strong correlation [Spearman's coefficient of rank correlation (rho): 0.995; P<.0001]. Magnetic resonance showed sensitivity of 100% (95% CI: 89.62-100.00%), specificity of 75% (95% CI: 20.34-95.88%), positive predictive value (PPV) of 97.14% (95% CI: 85.03-99.52%), and negative predictive value (NPV) of 100% (95% CI: 30.48-100.00%). CT showed a sensitivity of 100% (95% CI: 89.32-100.00%), specificity of 60% (95% CI: 15.40-93.51%), PPV of 94.29% (95% CI: 80.81-99.13%), and NPV of 100% (95% CI: 30.48-100.00%). CONCLUSIONS: CT demonstrated a potential supporting role in the evaluation of rectal cancer, showing a strong correlation with MRI.