Multislice spiral CT colonography in the evaluation of colorectal neoplasms

The purpose of our study was to evaluate the efficacy of multislice spiral CT colonography: 1) in the diagnosis and staging of colorectal carcinoma; 2) in the evaluation of the proximal colon in patients with stenosing neoplasms.

There were 33 patients (21 males and 12 females) with known colorectal carcinoma diagnosed by conventional colonoscopy. All patients enrolled in the study underwent both conventional colonoscopy followed by CT colonography on the same day. CT examination was performed using a multislice spiral CT scanner (Somatom Plus 4 Volume Zoom; Siemens, Erlangen, Germany). Imaging parameters were: slice collimation, 1 mm; slice thickness, 1 mm; table speed, 8 mm/sec; reconstruction interval, 1 mm; mAs, 80; kVp, 120; acquisition time, 25-32 sec. Image analysis was performed using a software package with volume-rendering capabilities (Vitrea 2.6; Vital Images, Minneapolis, USA). Image analysis consisted in the evaluation of: 1) number, size, and location of the lesions; 2) primary tumor staging. For the purposes of tumor staging, we utilized the TNM staging system. For the evaluation of parameters T and N, histologic examination on resected surgical specimens and lymph nodes served as the standard of reference. The presence of hepatic metastases was confirmed by means of partial surgical resection in patients with single metastasis or by means of intraoperative ultrasonography in patients with multiple metastases.

Conventional colonoscopy detected 33 carcinomas and 4 polyps and was incomplete in 9 cases (27.2% of all examinations) due to stenosing lesions. CT colonography provided adequate visualization of the whole colon in all patients with identification of 35 carcinomas (33 primary and 2 synchronous) and 10 polyps. Therefore, CT colonography correctly detected all lesions seen at conventional colonoscopy and yielded the additional identification of 2 synchronous tumors and 6 polyps located in the colon proximal to the primary stenosing neoplasm. Primary tumor staging with CT colonography was correct in 32 of 33 patients (accuracy, 96.9%)

Multislice spiral CT colonography detected all primary neoplasms, provided correct staging of 96.9% of tumors and visualized the whole colon even in patients with stenosing lesions. Considering the current limitations of the other procedures and the possibility of assessing both the colon and the extracolonic structures, multislice spiral CT colonography can be proposed as the initial diagnostic modality for pre-operative evaluation of patients with colorectal carcinoma.