ACR Appropriateness Criteria®
Clinical Condition: Suspected Lower Urinary Tract Trauma
Variant 1: Penetrating trauma, lower abdomen/pelvis.
| Radiologic Procedure |
Rating |
Comments |
RRL* |
| X-ray retrograde cystogram |
8 |
|
Med |
| CT cystography |
8 |
CT cystogram and retrograde cystogram are equivalent. If doing CT, do CT cystogram. |
High |
| CT bladder with contrast |
5 |
Routine enhanced CT by itself is inadequate to evaluate lower urinary tract for trauma. If needed to evaluate extraurinary pelvic organs. |
High |
| X-ray abdomen |
5 |
If any question of foreign body (e.g., bullet) |
Low |
| INV angiography bladder |
3 |
For persistent bleeding preliminary to embolotherapy. |
IP |
| X-ray intravenous urography |
2 |
Inadequate for lower urinary tract trauma. |
Low |
| X-ray retrograde urethrogram |
2 |
Unless suspected urethral injury (e.g., trajectory of knife or bullet) |
Med |
| US bladder and urethra transabdominal |
2 |
Ultrasound is usually not definitive. |
None |
| MRI bladder and urethra |
1 |
Not applicable to acute trauma. |
None |
| US bladder and urethra transurethral |
1 |
Ultrasound is usually not definitive |
None |
| NUC scintigraphy lower urinary tract |
1 |
Not applicable to acute trauma. |
Med |
| US bladder and urethra transrectal |
1 |
Ultrasound is usually not definitive. |
None |
| Rating Scale: 1=Least appropriate, 9=Most appropriate |
*Relative Radiation Level |
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Blunt trauma, lower abdomen/pelvis.
| Radiologic Procedure |
Rating |
Comments |
RRL* |
| X-ray abdomen |
9 |
|
Low |
| X-ray cystography |
8 |
|
Med |
| CT cystography |
8 |
CT cystogram and retrograde cystogram are equivalent. If doing CT, do CT cystogram. |
High |
| X-ray retrograde urethrogram |
5 |
Necessary if pelvic fracture present. |
Med |
| CT bladder with contrast |
5 |
Routine enhanced CT by itself is inadequate to evaluate lower urinary tract for trauma. If needed to evaluate extraurinary pelvic organs. |
High |
| INV angiography bladder |
3 |
For persistent bleeding preliminary to embolotherapy. |
IP |
| X-ray intravenous urography |
3 |
Inadequate for lower urinary tract trauma. |
Low |
| US bladder and urethra transabdominal |
2 |
Ultrasound is usually not definitive. |
None |
| US bladder and urethra transrectal |
1 |
Ultrasound is usually not definitive. |
None |
| NUC scintigraphy lower urinary tract |
1 |
Not applicable to acute trauma. |
Med |
| MRI bladder and urethra |
1 |
Not applicable to acute trauma. |
None |
| US bladder and urethra transurethral |
1 |
Ultrasound is usually not definitive. |
None |
| Rating Scale: 1=Least appropriate, 9=Most appropriate |
*Relative Radiation Level |
Variant 3: Blunt perineal trauma in the male (straddle injury).
| Radiologic Procedure |
Rating |
Comments |
RRL* |
| X-ray retrograde urethrogram |
9 |
|
Med |
| X-ray abdomen |
5 |
Necessary if strong suspicion of pelvic fracture present. |
Low |
| CT bladder with contrast |
2 |
To look for hematoma. |
High |
| CT cystography |
1 |
|
High |
| X-ray intravenous urography |
1 |
Inadequate for lower urinary tract trauma. |
Low |
| MRI bladder and urethra |
1 |
Not applicable to acute trauma. |
None |
| INV angiography bladder |
1 |
For persistent bleeding preliminary to embolotherapy. |
IP |
| US bladder and urethra transabdominal |
1 |
Transabdominal ultrasound not definitive. |
None |
| US bladder and urethra transurethral |
1 |
Transurethral ultrasound traumatic. |
None |
| NUC scintigraphy lower urinary tract |
1 |
Not applicable to acute trauma. |
Med |
| X-ray retrograde cystogram |
1 |
|
Med |
| US bladder and urethra transrectal |
1 |
Transrectal ultrasound painful. |
None |
| Rating Scale: 1=Least appropriate, 9=Most appropriate |
*Relative Radiation Level |
Summary of Literature Review
Lower urinary tract injury may be from blunt, penetrating, or iatrogenic trauma. About 10% of all trauma patients will manifest genitourinary tract involvement. About 70% of patients with bladder injuries from blunt trauma have associated pelvic fractures, with an average of 2.9 other injuries in multiple organ systems. Approximately 30% of patients with pelvic fractures will have some bladder injury, including bladder contusion. Major bladder injury occurs in about 10% of patients suffering from an anterior arch pelvic fracture. However, 25% of intraperitoneal bladder ruptures occur in patients without pelvic fracture. Simultaneous bladder ruptures from external trauma occur in 10% to 29% of male patients with traumatic rupture of the prostatomembranous urethra, with an average of 3.1 associated injuries per patient.
The degree of distension of the bladder with urine determines its shape and to some degree the injury it may sustain. An exceedingly light blow may rupture the fully distended bladder, but the empty bladder is seldom injured except by crushing or penetrating wounds. Pelvic scars or pre-existing pelvic pathology modify the situation.
Gross hematuria indicates urologic trauma. Presence of gross blood at the urethral meatus strongly suggests urethral injury. A Foley catheter should not be inserted without first doing a retrograde urethrogram to ensure urethral integrity. While grossly clear urine in a trauma patient without a pelvic fracture virtually eliminates the possibility of a bladder rupture, up to 2% of patients with bladder rupture may have only microhematuria.
Exactly how much blood in the urine necessitates investigation is a point of controversy in the literature. One study concluded that if cystography were restricted only to patients with more than 35 to 50 red blood cells/high power field (rbc/hpf), no perforation would have been missed in their series. Another group of researchers believes that cystography in blunt trauma should be restricted to those patients with gross hematuria, which they define as more than 200 rbc/hpf. They also feel that a retrograde urethrogram should be done first in males with a pelvic fracture. Another study concluded that since 90% of patients in their series of 103 patients with pelvic fracture did not have a bladder rupture, cystography may be safely reserved for those patients with pelvic fracture who are considered to be at high risk for such an injury. They limit cystography in pelvic fracture to patients with significant pubic arch involvement, gross hematuria, and/or hemodynamic instability.
Bladder Injury
| Type I |
Bladder contusion. |
| Type II |
Intraperitoneal rupture. |
| Type III |
Extraperitoneal rupture. |
| Type IV |
Combined injury. |
Bladder contusion (Type I) represents an incomplete tear of the bladder mucosa following blunt injury. The results of cystography are normal. The diagnosis of bladder contusion is usually established by exclusion in patients with hematuria following blunt pelvic trauma for which no other cause is found. While bladder contusion is generally regarded as the most common form of bladder injury following blunt trauma, it is not considered to be a major injury.
Intraperitoneal rupture (Type II) occurs when there is a sudden rise in intravesicle pressure as a result of a blow to the lower abdomen in a patient with a distended bladder. The increased intravesicle pressure results in rupture of the weakest portion of the bladder, the dome, where the bladder is in contact with the peritoneal surface. Intraperitoneal rupture accounts for approximately one-third of major bladder injuries. Approximately 25% of such injuries occur in patients without pelvic fracture. On cystography, contrast material extravasation into the paracolic gutters and outlining loops of small bowel will be present.
The classically described mechanism for extraperitoneal bladder rupture (Type III) is laceration of the bladder by a bone spicule in association with an anterior pelvic arch fracture. Recent data, however, have shown that cystograms in such patients often demonstrate that the site of contrast material extravasation is far removed from the site of fracture, and thus the validity of this mechanism has been questioned.
Extraperitoneal rupture represents approximately 60% of major bladder injuries. One group of investigators further subdivided extraperitoneal rupture into two groups. With simple extraperitoneal rupture, contrast extravasation is limited to the pelvic extraperitoneal space. With complex extraperitoneal rupture, contrast material extravasation may extend into the anterior abdominal wall, the penis, the scrotum, and the perineum. The presence of a complex extraperitoneal injury implies that the fascial boundaries of the pelvis have been disrupted by the injury. Such findings should not be mistaken as evidence of a coexisting urethral injury.
Combined bladder injury (Type IV) results when both intraperitoneal and extraperitoneal bladder injuries are present. This happens in approximately 5% of major bladder injuries.
Urethral Injury
Injuries to the male urethra can be classified into two main categories according to their mechanism of injury: 1) those associated with a fracture of the anterior pelvic arch (usually involving the membranous urethra), and 2) those occurring as the result of a straddle injury (usually involving the bulbous urethra). Any female urethral injury is rare and usually associated with pelvic disruption and/or vaginal laceration.
Some form of urethral injury occurs in about 5% of men who sustain a pelvic fracture when the prostate is sheared from its connection to the urogenital diaphragm as the puboprostatic ligaments are ruptured. The urethral injury is due to disruption of the soft tissues, rather than to a laceration by a bony spicule. A hematoma forms in the retropubic and perivesical spaces.
Straddle injuries occur as the result of a direct blow to the perineum when the urethra and corpus spongiosa are compressed between a hard object and the inferior aspect of the symphysis pubis. In most cases there is no pelvic fracture. Straddle injuries result in either partial or complete rupture of the bulbous urethra.
Male urethral trauma has been classified by Colapinto and McCallum based on the appearance of the retrograde urethrogram. This classification has been expanded to include all urethral trauma.
Urethral Injury Associated with Pelvic Fracture
| Type I |
Posterior urethra stretched but intact. |
| Type II |
Urethra disrupted at the membranoprostatic junction above the urogenital diaphragm. |
| Type III |
Membranous urethra disrupted, with extension to proximal bulbous urethra and/or disruption of the urogenital diaphragm (most common). |
| Type IV |
Bladder neck injury with extension into the urethra. |
| Type IVa |
Injury of the base of the bladder with periurethral extravasation simulating a true Type IV urethral injury. |
| Type V |
Partial or complete pure anterior urethral injury. |
Urethrography has improved the understanding of the mechanism of such injuries. In the past, the diagnosis of acute urethral injury often was based loosely on the clinical triad of 1) blood at the urethral meatus, 2) inability of the patient to void, and 3) a palpable urinary bladder. An inability to pass the catheter into the bladder also was considered diagnostic of a posterior urethral injury. It is now well established, however, that diagnostic catheterization is to be condemned since this procedure may convert a partial injury into a complete one. Because posterior urethral injuries are also seen with pelvic fractures, a retrograde urethrogram should be performed before inserting a catheter. Lack of pelvic and suprapubic tenderness; absence of penile, scrotal, or perineal hematoma; and a normal rectal examination support the integrity of the urethra.
Retrograde Urethrography
One study describes the widespread acceptance of retrograde urethrography (RUG) as the primary diagnostic procedure in patients suspected of having urethral injury.
Cystography
The diagnosis of bladder rupture is usually made easily on cystography when the injected contrast is identified outside the bladder. Retrograde cystography in evaluation of bladder trauma is called "procedure of choice," "mandatory," "the only way," "examination of choice," "keystone," "mainstay," and "absolute indication."
Adequate distention of the urinary bladder is crucial to finding a perforation, especially in instances of penetrating trauma, since most instances of a false negative retrograde cystogram were found in this situation.
Cystography requires plain film, filled film, and post-drainage films at a minimum. Half-filled film and obliques are optional. Bladder injury may be identified only on the post-drainage film in approximately 10% of cases. Cystography has an accuracy rate of 85% to 100% for detecting bladder injury. Only a properly performed cystogram should be used to exclude bladder injury.
Excretory Urography (Intravenous Pyelogram)
An intravenous pyelogram (IVP) is inadequate for evaluating the bladder and urethra after trauma because of dilution of the contrast material within the bladder and because resting intravesical pressure is simply too low to demonstrate a small tear. IVP has a low accuracy on the order of 15% to 25%. In only 5 of 23 patients (22%) studied was the diagnosis of bladder rupture made with IVP. One study found only 5 of 32 (16%), and another study found only 4 of 11 (36%).
Ultrasound
Transabdominal US findings in bladder rupture and urethral evaluation with endorectal probe have been described, but US has not been routinely used for evaluating the trauma patient. It is unlikely that a patient with significant posterior urethral or bladder rupture would tolerate evaluation with an endorectal probe. On the other hand, most or all serious trauma patients will likely be evaluated with CT because of the speed and accuracy of evaluation.
US can exclude associated visceral lesions such as solid or hollow organ rupture and nonspecific peritoneal fluid. The detection of peritoneal fluid in the presence of normal viscera or failure to visualize the bladder after the transurethral introduction of saline is considered highly suggestive of bladder rupture. As a practical matter, US is not definitive in bladder or urethral trauma and is almost never used.
Computed Tomography
CT cystography refers to the retrograde instillation of a minimum of 300-350 cc of diluted contrast media into the bladder followed by axial CT images of the pelvis. One study reported sensitivities of 95% overall but only 78% for intraperitoneal rupture. Routine CT, using excreted contrast only, cannot be relied upon entirely to diagnose bladder rupture even with a urethral catheter inserted and clamped. CT performed with excreted contrast only may demonstrate intraperitoneal or extraperitoneal fluid but cannot differentiate urine from ascites. The absence of pelvic ascites is strong evidence against bladder rupture. As with IVP, the bladder is usually inadequately distended to cause extravasation through a bladder laceration or perforation during routine abdominal and pelvic studies. A negative study cannot be entirely trusted.
One study reviewed the cystograms and CT examinations of 25 patients who had both studies as the initial evaluation of blunt abdominal trauma. Five of them had bladder rupture, three extraperitoneal and two intraperitoneal. All injuries were detected by both studies. The authors felt that delayed imaging or contrast instillation can provide the adequate bladder distention needed to demonstrate contrast extravasation from the injury site during CT. They continue to perform cystography in patients with compelling evidence of bladder injury but no extravasation demonstrated on CT. Another study stated that either retrograde cystography or CT is the diagnostic procedure of choice for suspected bladder injury.
The literature suggests that conventional and CT cystography are equivalent, with physician preference and diagnostic protocols generally defining which is used. Although CT is not the technique of choice for urethral injuries, it is performed so frequently that urethral injuries are inevitably identified on CT performed for pelvic trauma. Findings can include displacement of the prostate and bladder, extravasation of contrast media, and hematomas.
Angiography
Angiography can be useful in identifying an occult source of bleeding and can guide its subsequent therapeutic embolization.
Nuclear Imaging
Because of its low resolution, nuclear imaging has not been applied to lower urinary tract injuries.
Magnetic Resonance Imaging
Because of the difficulty of monitoring a seriously injured patient in a strong magnetic field, magnetic resonance imaging (MRI) currently has little place in the evaluation of acute bladder and/or urethral trauma. Use of MRI has been described for later evaluation of urethral injury.
Abbreviation
- CT, computed tomography
- IP, in progress
- INV, invasive
- Med, medium
- MRI, magnetic resonance imaging
- NUC, nuclear medicine
- US, ultrasound
