Virtual cystoscopy by intravesical instillation of dilute contrast medium: preliminary experience

We determined whether virtual cystoscopy based on helical data sets can yield urinary capabilities similar to those achieved by fiber-optic cystoscopy.

A total of 11 patients with ultrasound detected bladder tumors underwent pelvic CT as a single volumetric scan after preliminary bladder distention with saline mixed with contrast medium using a 6Fr infant feeding tube. Cystoscopy was simulated based on a 3-dimensional helical CT data set in real time. Source raw CT data for virtual cystoscopy were reconstructed and navigation was done in real time using surface rendering navigation software. These images and findings were then compared with conventional cystoscopy findings.

An attenuation gradient of 350 HU between the vesical mucosa and urine was noted. Two of the 14 tumors (11 patients) were missed and each was 0.7 cm. All tumors greater than 0.9 cm were detected. Overall sensitivity was 85.7%. There were no false-positive findings. There was good correlation with tumor location and size. The ureteral orifices and their relationship to the tumor were also well appreciated. Subtle mucosal changes on conventional cystoscopy were not delineated by virtual cystoscopy.

Our method of instilling dilute contrast medium in the bladder offers an excellent attenuation gradient. The overall sensitivity of tumor detection is better than that reported for intravenous contrast medium and pneumocystoscopy.