Monday, April 9, 2012

Virtual Cystoscopy


      Bladder cancer is one of the common urological malignancies, with the need for life-long follow-up. It represents 4.5% of new cancer diagnoses. The gold-standard of current diagnosis, as well as follow-up involves direct visualisation of the bladder mucosa with the use of a flexible/rigid cystoscopy. 

There are however, problems with instrumentation of the urinary tract for visualisation, including urethral trauma, which may cause late stricture, as well as infection, and failure to visualise the mucosa due to debris or blood. Contraindications include acute cystitis, prostatitis, urethritis, occlusive prostatic enlargement, and urethral stricture.

CT virtual cystography (VC) has emerged as a potentially viable alternative to current invasive methods of bladder visualisation. Using 3D technology, the technique was first proposed by Vining and co-workers in North Carolina (USA), and either involves:

1). Passing a urinary catheter, and using double contrast with CO2 and radio-opaque dye, or:
2). Using IV contrast, with no need to instrument the urinary tract.

VC can be performed using either CT or MRI, though the latter is time-consuming, expensive, and labour intensive (though slightly more sensitive and specific). Sensitivity and specificity of CT VC has been reported in a number of papers since 1995 to be as high as 95% and 87% respectively for identifying bladder tumours, and 95% and 93% respectively for identifying abnormal bladder mucosa due to all causes.

Problems include the size of visible lesions, being poor for small (<4mm), and flat lesions such as carcinoma in-situ. Another disadvantage is that the urologist is unable to manage any lesion found immediately, for example by fulguration, and cannot provide tissue diagnosis. It will place an extra burden on already busy CT scanners, and will require specialist review of images.

Whilst it is recognised that the limitations of CT virtual cystoscopy currently prevent its mainstream clinical use, it is hoped that in the future, with advances in technology, the technique may be of practicable use.

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