Dynamic three-dimensional spiral computed tomographic cysto-urethrography: a novel technique for evaluating post-traumatic posterior urethral defects.
OBJECTIVE: To present a new method of identifying the anatomy of posterior urethral distraction defects (PUDDs) using three-dimensional spiral computed tomography/cysto-urethrography (CTCUG), as conventional two-dimensional CUG can give a false interpretation of the exact anatomy. PATIENTS AND METHODS: Twenty-one patients presenting with a PUDD were assessed between February 2001 and October 2002. All patients initially underwent combined ascending and micturating CUG (ACUG), followed by CTCUG analysed using special software. In this technique all soft-tissue densities were subtracted from the volume of interest leaving only high-density images, i.e. pelvic bony structure and the contrast medium-filled bladder and urethra. The images were taken over a sequence and 36 different images viewed by 'roll and spin' techniques, each of which had a different plane of vision. Images were supplied as static CT films and as a movie on a compact disk using a computer program. RESULTS: The technique allows one CT image to be viewed from 36 different angles both dynamically and statically, allowing the surgeon the unique opportunity to view the PUDD through several planes and precisely identify its anatomy. By comparing the data obtained with this technique to those obtained by conventional ACUG, and each in relation to the operative findings, the following aspects could be more thoroughly evaluated by CTCUG: the location of the distraction injury, the length of the distraction defect, the degree and direction of urethral end-alignment, the relation of the ectopic bony fragments and bone callus to the urethra, and the presence of various pathological defects, e.g. fistulae, false passages and diverticulae. CONCLUSION: With CTCUG, both static and dynamic images can be obtained, allowing the easier staging of a PUDD and thus better surgical planning and consequently better results from reconstruction.