How to Perform a Retrograde Cystogram
Retrograde cystography is the gold standard radiographic technique for demonstrating bladder ruptures. It will not miss a perforation, as long as
■ the bladder is adequately filled;
■ a postdrainage image is taken once the bladder has been emptied of contrast.
Both aspects of the technique are important. If the bladder is not properly expanded with contrast, a perforation may be obscured
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FIGURE 5.19. A normal urethrogram. a: Lateral projection. b: Anteroposterior projection.
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by a 'plug' of omentum or small bowel temporarily sealing the hole (false-negative cystograms have been reported, when volumes of 250 mL or less were used for the cystogram; Cass and Luxenberg 1987). Conversely, a posterior perforation can sometimes be obscured by a mass of contrast filling the bladder and the leak of contrast only becomes apparent as a 'whisper' of contrast outside the bladder when the bladder has been emptied (approximately 10% of bladder perforations are diagnosed on the postdrainage film).
Pass a small (e.g., 12 or 14 Ch) catheter into the bladder and, using gravity, instill approximately 400 mL of contrast (in children, 60 mL plus 30 mL per year of age up to a maximum of 400 mL) into the bladder. Again, we use Urografin 150. Images may be taken fluoroscopically or several static images can be taken as the bladder is filled and then emptied.
Alternatively, a CT cystogram can be done. If the patient is going to have a CT scan done anyway (and it usually is done), it is simpler to image the bladder with CT than fluoroscopically (the patient would have to be moved to another room in the radiology department to allow this to be done). Diluted contrast should be used if a CT cystogram is to be done because undiluted contrast is so dense that it produces poorer images. The key point in CT cystography is to instill the contrast retrogradely through a catheter inserted into the bladder—CT cystography using intravascularly administered contrast can miss bladder perforations. Haas et al. (1999) found that retrograde cystography successfully diagnosed all of 15 cases of bladder rupture due to blunt trauma, but spiral CT with intravenous contrast and catheter clamping to distend the bladder successfully diagnosed only nine of these 15 ruptures. CT correctly diagnosed four of five (80%) intraperitoneal ruptures and 6 of 11 (55%) extraperitoneal ruptures.