Virtual CT colonoscopy versus conventional colonoscopy: a prospective study

Diagnosis of colorectal diseases might be a challenge. This prospective study aimed to evaluate virtual CT colonoscopy (CT colonography) as a new diagnostic modality in colorectal diseases.

Thirty-two patients (22 males and 10 females, mean age 47 years) with different colorectal complaints were investigated by CT colonography. Scanning parameters were collimation of 5mm, table speed of 6.25mm/s and pitch of 1.25. All images were evaluated in axial slices, reformatted images with endoluminal and extraluminal views. All patients were re-examined by the conventional colonoscope. The CT colonography and the colonoscopy findings were correlated.

CT colonography suspected colorectal malignancy in 14 patients, diagnosed colorectal polyps in 4 (out of 6), suspected inflammatory bowel diseases in 5 (out of 6), showed colonic diverticulae in 3 (out of 4), and found no abnormality in 2 patients. CT colonography displayed the proximal colon above the obstructing lesion in extraluminal views, fungating mass in endoluminal view and accurately localized the lesion. In inflammatory bowel diseases, segmental (in 4 patients) or skipped (one patient) wall thickening, loss of colonic haustration (3 patients) and pseudopolyps (one patient) were detected. Superficial ulcers were missed. Endoluminal images displayed the orifices of the diverticulae in 3 patients. The CT colonography sensitivity was 86.7% and its specificity was 100%.

The high resolution and multiple image display of CT colonography allow detection of many colorectal lesions. CT colonography is also a noninvasive imaging modality that is particularly valuable in poor risk patients and for colorectal examination proximal to an obstructing lesion.