2. The bladder is often pushed upward by the pelvic haematoma that follows any serious pelvic fracture. It can be difficult, even for the experienced urologist, to locate the bladder for safe suprapubic puncture. The catheter can inadvertently be inserted into the pelvic haematoma. At best, it will clearly be in the wrong position and bladder drainage will not have been achieved; at worst, infection can be introduced into the pelvic haematoma, with disastrous consequences.
3. A catheter of adequate size should be inserted into the bladder. As there is likely to be some bleeding from the bladder
5. TRAUMATIC UROLOGICAL EMERGENCIES 93
in the days following placement of the catheter, if too small a catheter has been used, it could become blocked by clots. Formal open placement of a suprapubic catheter allows a larger catheter to be placed in the bladder than is possible through a percutaneous trocar, where the maximum catheter size is 14 Ch.
In practice, however, infection of metal plates is rarely seen, and it has been suggested that as long as the bladder is approached from a high-enough position (so as to avoid the pelvic haematoma) a percutaneous suprapubic catheter may be safely placed (McAninch 2002). Certainly, if the patient is unstable, a percutaneous suprapubic catheter should be inserted, rather than the patient undergoing a general anaesthetic just for insertion of a suprapubic catheter. Once the patient has been stabilised, a cystogram can be done to exclude a bladder injury.
How to Perform a Retrograde Urethrogram
The contrast agent used varies from hospital to hospital. We use Urografin 150 (sodium amidotrizoate and meglumine amidotri-zoate), but other contrast agents can be used. A small (e.g., 12 or 14 Ch) catheter is placed in the fossa navicularis of the penis (approximately 1-2 cm from the external meatus). To prevent contrast spilling out of the urethra and to hold the catheter in place, either inflate the catheter balloon with 2 mL of water or apply a penile clamp to the end of the penis. Ideally continuous screening (fluoroscopy) should be done as contrast is gently instilled until the entire length of the urethra has been demonstrated. Alternatively, static images may be taken at intervals. Remember, as the urethra passes through the pelvic floor (the membranous urethra) there is a normal narrowing, and similarly the prostatic urethra is narrower than the bulbar urethra (Fig. 5.19).