Bladder Trauma Imaging

Bladder trauma is a semi-emergent condition, especially trauma that results in uroperitoneum. In such injuries, sepsis can develop within 24 hours if surgery with repair is not performed. Radiologic examination is of paramount importance and should be performed to identify and classify the injury and to plan surgical repair, but it should not hinder patient treatment and stabilization. ^[1] Several radiologic evaluations are appropriate, ranging from computed tomography (CT) cystography to basic retrograde cystography. All have been moderately well studied and require different equipment, locations, protocols, and operator expertise. It is always necessary to consider the stability of the patient's condition with regard to airway patency and circulation during the transfer and radiologic evaluation of the patient. Trauma continues to be a major cause of morbidity and mortality in all areas of the world. Many immediately life-threatening insults are to the vital organs or to their blood supplies, and many diagnostic skills and studies are meant to rapidly reveal these complications. However, other life-threatening conditions must be addressed in a timely manner to avoid morbidity and, occasionally, mortality.

Ideally, these conditions are diagnosed simultaneously, rather than individually, and the search for a universally applicable study is under way. Immediate surgery or another approach is commonly the diagnostic and therapeutic procedure of choice if the patient is exsanguinating or if his or her condition is deemed otherwise unstable.

The radiologic characteristics of bladder trauma are demonstrated in the images below. ^{[2, 3]}

In a retrospective study of patients with bladder rupture from blunt trauma, mortality rate was 11%, mean injury severity score was 29, and mean length of hospital stay was 15 days. ^[4] Most ruptures were diagnosed by CT cystography. Pelvic fracture was present in 80%, hollow viscus injury in 34.5%, colon injury in 24%, and rectal injury in 9.3%. Pelvic fracture was present in essentially all patients with extraperitoneal bladder rupture, and hollow viscus injuries were present more often in patients with intraperitoneal bladder rupture. ^{[2, 5]}

Preferred examination

The extent and type of radiologic evaluation required depends on the patient's condition and on the size of the area that may be affected. Many patients in stable condition require extensive screening, which means that diagnostic procedures should ideally provide views of large areas following quick and common preparation. For many patients in unstable condition or in patients with penetrating abdominal injuries who are immediately treated in the operating room (at the discretion of the surgeon), intraoperative radiologic evaluation is needed. ^{[6, 7, 8, 9]}

Retrograde cystography, performed after urethrography, was considered the criterion standard for evaluation of bladder trauma. However, support has grown for using CT cystography in proper diagnosis. Initial studies were not indicative of the reliability of CT scanning when retrograde contrast enhancement was not used. However, contemporary studies have overwhelmingly demonstrated that the technique is sensitive and accurate, provided that adequate bladder distention (with at least 350-400 mL of contrast material) is achieved before the study is performed. In diagnosing bladder rupture, CT cystography, performed with 400 mL of contrast material that is administered in a retrograde fashion, is as accurate as plain radiography with retrograde cystography. ^{[6, 10, 11]}

Retrograde cystograms have long been used for detecting bladder rupture. ^[12] They are nearly 100% sensitive for detecting rupture, provided that adequate distention is accomplished and that postvoiding images are obtained. However, they are time consuming, the examinations are costly when one considers their value relative to their benefit, and they require extra radiography that does not occur in addition to necessary trauma evaluation. Furthermore, they are not useful in thoroughly evaluating other structures present in the abdomen and pelvis.

CT retrograde cystograms are completed in the radiology suite when routine spiral scans of the head, neck, chest, and abdomen and pelvis are performed. CT retrograde cystography generally requires the same retrograde introduction of contrast agent as does retrograde cystography. However, unlike plain radiography, the technique does not require multiple images, including postvoiding and oblique views. Thus, this procedure is less time consuming and, some would argue, less costly. At 1 hospital cited in the literature, the cost of CT cystography was $500 or more, a marginal increase over a plain radiographic examination. Costs should be specifically evaluated at each institution.

A final step is the washout study. After the full-bladder findings are recorded (on radiographs or CT scans), the bladder is drained. If no residual contrast enhancement is present, the examination is completed, and the results are negative. If residual contrast enhancement is present in the bladder area, fluid (eg, sterile water) is used to lavage the bladder. If no residual contrast enhancement is noted after drainage, the examination is completed, and the results are negative. If contrast enhancement remains, a bladder wall injury is present.

CT cystography may be used somewhat less often in patients who are not undergoing CT scanning for another reason. In a study of 157 patients with hematuria, an absence of free fluid on abdominopelvic CT scans was a strong negative predictor of bladder rupture. ^[13] In such patients, not performing cystography may be reasonable.

Further study into this matter is warranted. Perhaps 1 of the greatest advantages of retrograde CT cystography with prior abdominopelvic CT scanning is the ability to detect renal parenchymal injury. In these patients, intravenous urography is not necessary, as it commonly is with traditional retrograde cystography.

A few studies have focused on delayed evaluation of the bladder. For example, the use of contrast material for chest and abdominal CT scanning (for which a large amount of contrast material is routinely required) has been studied. In these examinations, the contrast agent was allowed to distend the bladder in an anterograde fashion. However, in such cases this distention occurs at the expense of valuable time, because the Foley catheter should be clamped for at least 20-30 minutes to have any opportunity to achieve accurate results. Furthermore, if preexisting renal insufficiency or renal pedicle injury is present, this method may be inadequate.

The author does not recommend this diagnostic strategy for the reasons mentioned. Because study results have also cast doubt on the consistent accuracy of this method in the evaluation of blunt trauma, its use is discouraged.

Limitations of techniques

Cystography generally has served to greatly decrease trauma morbidity and mortality by helping to successfully screen for bladder rupture. Little doubt exists concerning the accuracy of plain film cystography, as long as a bladder hematoma does not occlude a rift in the bladder wall and prevent dye from flowing out into the surrounding spaces. The primary concern is that the examination often does not occur in parallel with other radiologic examinations of patients with trauma who require CT scanning.

A caveat should be noted: a normal cystogram finding does not exclude a bladder rupture. At surgery, intraperitoneal or extraperitoneal extravasation may be found. The consideration in this scenario is the spasm of the detrusor muscle, which is possibly secondary to the irritation effect of the contrast medium, which causes a leak to become sealed. With general anesthesia, the detrusor relaxes; this is associated with the eventual intraoperative leak.

CT cystography is faster than are plain radiographic studies; moreover, it has no labor-intensive requirements for completion, and it can be used to diagnose large hematomas of the bladder, which potentially could overlie an occult breech in the bladder wall. Furthermore, classification of bladder injury patterns requires CT scanning because cystography addresses perforations but not more subtle findings.

The cost in each prospective hospital should be considered, because the monetary costs, which favor classic cystography, may not reflect actual benefits. For instance, because radiographic technologists currently are in short supply, increasing their use adds to the expense. Furthermore, time is valuable in the trauma setting, especially because patients in seemingly stable conditions can deteriorate quickly, and a more rapid evaluation can facilitate their transfer to the trauma intensive care unit or operating room.

In general, the author believes that evaluation with CT cystography is the study of choice when patients already require transfer to the radiology suite for CT scanning evaluation. This is true especially when microscopic hematuria is present and a possibility of renal trauma exists.

Ultrasonography imay be helpful in diagnosing bladder contusion, but it has been demonstrated to be unreliable in diagnosing bladder rupture. ^[7]

For excellent patient education resources, see eMedicineHealth's patient education article Blood in the Urine.

Retrograde cystography was considered the criterion standard for detecting bladder rupture (see the images below), but CT scanning is now becoming the most recommended study for evaluation of bladder trauma.  Reliability depends on several variables. To obtain dependable results, adequate bladder distention, requiring 350-400 mL of contrast material, is of paramount importance. To correctly perform the study, postevacuation images also should be obtained.

With this method, diagnostic accuracy has been reported to be near 100%. False-negative findings occur, most commonly in association with penetrating injury. In this scenario, wound margins are believed to align well and prevent leakage. Some authors have recommended fluoroscopy, with the patient in the Trendelenburg position during the examination to increase sensitivity. Others have suggested instilling contrast material until discomfort occurs. Rarely, as mentioned before, a bladder hematoma also may block the wound orifice and prevent the leakage of contrast material. ^{[6, 11, 13, 14]}

CT scanning is rapidly becoming the most recommended study for trauma evaluation of the bladder. It is fast, it can be used to evaluate other urologic organs, and it requires no additional manipulation of the patient beyond that needed for routine evaluation. Furthermore, the literature suggests that plain abdominopelvic CT scanning may have a high negative predictive value for bladder rupture in a select subset of patients, even without cystography. This makes delaying cystography until after routine abdominopelvic CT scanning even more valuable. However, this approach applies if no hematuria is present and if no free fluid is observed anywhere in the abdomen or pelvis during routine abdominopelvic contrast-enhanced CT scanning. ^{[6, 9]}

One advantage of CT is its ability to review multiplanar reformatted images. CT can detect unusual fluid collections, unusual gas collections, an abnormal location of a Foley catheter, or a defect in an enhancing bladder wall. ^[15]

Additionally, all studies reviewed by the author demonstrated that bladder ruptures were not seen in patients in whom no free fluid was observed on standard contrast-enhanced CT scans, regardless of the degree of hematuria. Further study is needed to determine whether cystography, either CT scanning or standard cystography, can be safely omitted in this scenario.

Many patients do not present with the above parameters, and when these parameters are not met, routine contrast-enhanced abdominopelvic CT scanning is highly inaccurate and insensitive in detecting bladder rupture. However, the results of CT cystography have been shown to be diagnostic. Overall, it is 95% sensitive and 100% specific in detecting bladder rupture. A group performing 1 small study took exception, suggesting that it is slightly less accurate when intraperitoneal rupture is present, with 80% sensitivity and 99% specificity. However, this is not a common concern. Furthermore, CT cystography can be used to fully classify bladder injury beyond noting whether a rupture is intraperitoneal or extraperitoneal (see the images below). ^[14] Studies have demonstrated that CT cystography has requirements similar to those of retrograde cystography for diagnostic accuracy. Specifically, good bladder distention, provided with 350-400 mL of contrast material by means of retrograde infusion, is required.