BACKGROUND AND AIMS To determine the sensitivity and specificity of computed tomography (CT) pneumocolon in the detection of colorectal neoplasms.

RESULTS On conventional colonoscopy 13 invasive colorectal carcinomas were detected in 13 patients, and 118 polyps in 63 patients (14 polyps were ⩾1 cm in diameter, 25 were 6–9 mm, and 79 were ⩽5 mm). CT pneumocolon detected all 13 cancers, two false positive cancers, but only 20 polyps (seven were ⩾1 cm). This resulted in a sensitivity of 100% (95% confidence interval (CI) 87–100%) and specificity of 99% (95% CI 97–100%) for detection of invasive carcinoma, and a sensitivity of 73% (95% CI 56–90%) and specificity of 94% (95% CI 91–98%) for detection of invasive carcinoma and/or ⩾1 cm polyps. CT pneumocolon also identified invasive carcinoma not seen at colonoscopy because of incomplete examination in three patients, and detected metastases in six colorectal carcinoma patients and extracolonic carcinoma in a further seven patients.

CONCLUSIONS CT pneumocolon had a high sensitivity and specificity for detection of invasive colorectal carcinoma but not colorectal polyps. CT pneumocolon may be suitable for initial investigation of patients with symptoms of colorectal malignancy.