Thus, while the majority of patients with pelvic fractures do not have bladder injuries, a substantial minority (1 in 10) do, and almost half of these are intraperitoneal. Missing a diagnosis of bladder perforation in this situation can have disastrous consequence, and for this reason all patients who have a pelvic fracture should undergo a urethrogram and a cystogram. up to 10% of patients with bladder rupture may have no macroscopic haematuria and a further 10% may have only microscopic haematuria (Cass and Luxenberg 1987). Absence of haematuria is more common in patients with intraperitoneal bladder rupture, than in those with extraperitoneal perforation.
Combined Bladder and Posterior Urethral Injuries Following Pelvic Fracture
If the bladder has been ruptured by a blunt injury causing a pelvic fracture, have a high index of suspicion for an associated urethral injury. About one third of patients with a traumatic blunt bladder rupture have associated injuries to other urinary structures, most commonly the urethra. Approximately 5% to 10% of patients with a pelvic fracture and bladder rupture also have a posterior urethral rupture (Cass and Luxenberg 1987). In a series of pelvic fractures, Cass (1988) found bladder ruptures in 6%, urethral rupture in 2%, and combined bladder and ure-thral rupture in 0.5%.
Urethral Injuries Associated with Pelvic Fractures
The posterior urethra (essentially the membranous urethra) is injured with roughly the same frequency as the bladder in subjects who sustain a pelvic fracture, occurring in between 5% and 15% of such cases. The great majority of posterior urethral injuries occur in association with pelvic fractures and approxi-
5. TRAUMATIC UROLOGICAL EMERGENCIES 91
mately 10% to 20% of patients with a posterior urethral injury have an associated bladder rupture (Cass et al. 1984) (specifically bilateral pubic rami fractures and especially those with sacroil-iac joint displacement; Koraitim 1996). Very occasionally a posterior urethral injury can occur in the absence of an associated pelvic fracture following blunt trauma to the perineum.