5. TRAUMATIC UROLOGICAL EMERGENCIES 99
microscopic haematuria. However, remember, the absence of macroscopic haematuria does not necessarily mean the absence of a bladder injury. Have a low threshold for arranging imaging studies.
As discussed above, there are two main ways of imaging the bladder—conventional retrograde cystography or CT cystogra-phy. Whatever method is used, several points of technique are worth emphasising. First, the bladder must be adequately distended with contrast. If only 100 mL or so of contrast is instilled into the bladder, a clot, omentum, or small bowel may continue to 'plug' the perforation, which therefore may not be diagnosed. Use at least 400 mL of contrast in an adult and 60 mL plus 30 mL per year of age in children up to a maximum of 400 mL in children. Second, images must be obtained after the contrast agent has been completely drained from the bladder (a postdrainage film). A whisper of contrast from a posterior perforation may be obscured by a bladder distended with contrast.
In extraperitoneal perforations, extravasation of contrast is limited to the immediate area surrounding the bladder (Fig. 5.20). In intraperitoneal perforations, loops of bowel may be outlined by the contrast (Fig. 5.21).
Extraperitoneal and Intraperitoneal Perforation During Resection of a Bladder Tumour (TURBT)
When a bladder cancer is being resected, its location will determine the likelihood of a perforation being extraperitoneal or intraperitoneal. A perforation at the neck of the bladder or on the trigone is not adjacent to the peritoneal cavity, and therefore such a perforation cannot be intraperitoneal. However, when a tumour is located in the dome of the bladder, immediately beneath which is the peritoneum, it is quite possible for an intraperitoneal perforation to occur.
Small perforations into the perivesical tissues are not uncommon when resecting small tumours of the bladder. Perivesical fat is seen. As long as you have secured good haemostasis and all the irrigating fluid (if you use this) is being recovered, no additional steps are required except that perhaps one should leave the catheter in for 4 days rather than 2. You may decide to irrigate the bladder with irrigating fluid. Alternatively, allow the patient's own urine output to wash out the bladder (the urine output can be increased by giving a low dose—20-40 mg—of intravenous frusemide).