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Original Research |
1 Department of Diagnostic Radiology and Organ Imaging, Prince of Wales
Hospital, Shatin, Hong Kong.
2 Department of Radiology, Massachusetts General Hospital, Boston, MA
02114.
Received June 7, 2005;
accepted after revision September 18, 2005.
Presented at the 2005 annual meeting of the Radiological Society of North
America, Chicago, IL.
Abstract
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MATERIALS AND METHODS. The patient cohort was composed of trauma patients with clinically or CT-suspected bladder ruptures who were evaluated with CT cystography using two different MDCT scanners at our level 1 trauma center. The patients were identified through Folio, a radiology research tool software system. The CT cystography results were compared with the findings at surgery, clinical follow-up, or both.
RESULTS. Between January 1, 2000, and December 31, 2004, 234 patients were examined in our level 1 trauma center with CT cystography. From the total of 234 examinations, 216 (92.3%) were interpreted as negative and 18 examinations (7.7%) were interpreted as positive. On the 18 positive examinations, 11 were extraperitoneal bladder rupture, five were intraperitoneal bladder rupture, and two were combined intraperitoneal and extraperitoneal bladder rupture. Surgical bladder exploration and repair were performed in nine of the 18 cases. Seven (77.8%) of the nine cases had operative findings consistent with the CT cystogram findings. The overall sensitivity and specificity of CT cystography in diagnosing bladder rupture were each 100%. For extraperitoneal bladder rupture, the sensitivity and specificity were 92.8% and 100%, respectively. For intraperitoneal rupture, the sensitivity and specificity were 100% and 99%, respectively.
CONCLUSION. CT cystography is accurate for diagnosing bladder rupture. Sagittal and coronal multiplanar reformations may be helpful in identifying most sites of bladder rupture.
Keywords: bladder trauma • CT cystography • multiplanar reformation
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Accurate identification of bladder injury is of paramount importance for proper management. Surgical repair is required for intraperitoneal rupture and combined intraperitoneal and extraperitoneal rupture. Catheter drainage is required for extraperitoneal rupture, whereas contusion can be managed conservatively. Delay in the diagnosis and treatment of bladder trauma may increase patient morbidity and mortality. Therefore, rapid diagnosis is essential for optimal patient management [3].
In the past, conventional cystography was considered the standard procedure for evaluating patients with suspected bladder injury [4-6]. However, it is time-consuming, cannot provide information regarding other pelvic structures, and is sometimes limited by the presence of overlying fracture fragments or fixation devices.
CT is now considered to be a diagnostic procedure of choice in the evaluation of abdominal and pelvic injury after blunt trauma. The conventional CT protocol for abdominal trauma may or may not show the presence of bladder trauma because visualization of bladder rupture on CT requires the bladder to be filled with fluid and under pressure. Therefore, if a conventional abdominal trauma CT examination fails to show bladder rupture and bladder rupture is suspected, especially when water-dense fluid is seen in the peritoneal cavity, CT cystography is indicated. The value of CT cystography has been evaluated by other investigators [4, 5] who concluded that it was as accurate as conventional cystography in diagnosing bladder trauma.
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The axial CT images and MPR images, including sagittal and coronal reformatted images of all cases, were retrospectively analyzed by one of the authors using a PACS workstation (IMPAX, Agfa). The images were evaluated to assess the types of bladder injury (extraperitoneal rupture, intraperitoneal rupture, combined intraperitoneal and extraperitoneal rupture) and also the sites of bladder injury in different planes. These findings were compared with the operative findings and the progress of the patient's clinical condition during the hospital stay—for example, any persistent hematuria, abdominal pain, and follow-up imaging (CT or conventional cystography).
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Gross hematuria was present in 46 of the 234 patients, including all 18 patients with bladder rupture. Microscopic hematuria was seen in 111 of the 234 patients and no hematuria in 77. No bladder injury was seen in these two groups of patients.
Bladder exploration and repair were performed in nine patients with positive CT cystography results (three extraperitoneal rupture, four intraperitoneal rupture, two combined intraperitoneal and extraperitoneal rupture). The operative findings were consistent with the CT cystogram findings in seven of the nine cases. In one of those cases, CT was interpreted initially as combined intraperitoneal and extraperitoneal rupture but on surgical exploration was found to be extraperitoneal rupture only. However, on retrospective review only extraperitoneal rupture was seen on CT (Figs. 4A, 4B, and 4C). In one of the nine cases, CT was interpreted as intraperitoneal bladder rupture with contrast extravasation into the peritoneal space. A small amount of fluid was seen in the extraperitoneal space lateral to the bladder wall but no contrast extravasation to the extraperitoneal space was seen. Operative exploration revealed combined intraperitoneal and extraperitoneal rupture (Figs. 5A and 5B). The specific type of bladder rupture was therefore correctly identified on CT cystography in seven of nine patients (77.8%). In the seven of 11 patients with extraperitoneal rupture, the treatment was conservative. Follow-up imaging performed 7-38 days after initial injury in six of the seven (three CT cystography and three conventional cystography) did not show further rupture (Fig. 2D).
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The overall sensitivity and specificity of CT cystography in diagnosing bladder rupture were both 100%. For detection of extraperitoneal bladder rupture, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CT cystography were 92.9%, 100%, 100%, and 99.5%, respectively. For detection of intraperitoneal bladder rupture, the sensitivity, specificity, PPV, and NPV of CT cystography were 100%, 99.6%, 85.7%, and 100%, respectively.
The axial images were retrospectively compared with coronal and sagittal images from MPR. One case (Figs. 4A, 4B, and 4C) with an initial diagnosis of combined intraperitoneal and extraperitoneal rupture was found to have only extraperitoneal rupture on exploration. The MPR images were retrospectively reviewed and showed no contrast extravasation in the peritoneal space. For the case with a CT cystography diagnosis of intraperitoneal rupture but an operative diagnosis of combined intraperitoneal rupture and extraperitoneal rupture, the axial and MPR images were retrospectively reviewed (Figs. 5A and 5B), but again no contrast extravasation was seen in the extraperitoneal space in any of the three planes.
Through the axial images, we could identify the sites of bladder rupture in 14 of the 18 patients (11, extraperitoneal rupture; 1, intraperitoneal rupture; and 2, combined intraperitoneal and extraperitoneal rupture). In the remaining four patients with intraperitoneal rupture, the site of rupture was at the bladder dome but could not be well shown in axial images (Figs. 3A, 3B, 3C, and 3D). However, through the coronal and sagittal images from MPR we could identify all the bladder sites, including the four cases not seen in the axial images.
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Conventional cystography has been regarded as the standard for the evaluation of bladder trauma. However, conventional cystography is sometimes difficult in a trauma setting, particularly if the patient is on a spinal board, and turning a patient with pelvic trauma may be not be possible. In addition, conventional cystography is time-consuming, cannot provide information on surrounding structures, and is sometimes limited by the presence of the overlying fracture fragment or fixation devices in pelvic fracture.
CT is generally accepted as an imaging technique of choice for the evaluation of patients with multiple injuries, and the concept of integrating CT scanners into the context of the emergency department has contributed to increasing the use of CT for evaluation of multitrauma patients [2, 9]. CT is therefore considered essential for bladder trauma assessment. In addition to the high level of diagnostic certainty, there is the further advantage of performing the entire examination at one location. The patient does not have to be transported from CT room to fluoroscopy room for conventional cystography.
The accuracy of CT for evaluation of bladder trauma has been assessed. Mee et al. [10] reported two cases of missed bladder rupture by CT in which the bladder was filled by the contrast agent in an antegrade fashion by clamping the Foley catheter while the delayed scan was taken. It was concluded that inadequate bladder distention was a limitation of CT, and retrograde infusion of contrast agent was advocated. A subsequent study by Lis and Cohen [5] showed that CT cystography is at least as accurate as conventional cystography in assessing bladder injury. In a prospective study by Peng et al. [4], which used CT cystography to screen 55 patients with hematuria and blunt abdominal trauma, five patients were identified as having bladder rupture and the diagnoses were confirmed intraoperatively. There were no false-positive results. Diagnoses for the remaining 50 patients with negative CT cystography results were confirmed on conventional cystography. In a retrospective review by Deck et al. [6], 44 of 316 patients had bladder rupture, and CT cystography was used to identify 42 cases. The sensitivity, specificity, PPV, and NPV for CT cystography in diagnosing extraperitoneal rupture were 97%, 100%, 100%, and 99%. The sensitivity, specificity, PPV, and NPV for CT cystography in diagnosing intraperitoneal rupture were 78%, 99%, 70%, and 99%.
In our study using MDCT, the results were comparable with the study by Deck et al. [6] using helical CT. There were no false-negative results in our study. The sensitivity of CT cystography in diagnosing intraperitoneal rupture in our study was higher than that found by Deck et al. (100% vs 78%), whereas the specificity remained the same (both 99%). We postulated the use of MDCT may increase sensitivity with no change in specificity in diagnosing intraperitoneal bladder rupture. The diagnosis of intraperitoneal bladder rupture is important because surgical repair is required, and delay in diagnosis or treatment may increase morbidity and mortality.
There were two cases with discrepancy in the type of bladder rupture. The first case was interpreted as combined intraperitoneal and extraperitoneal rupture but exploration found both to be extraperitoneal rupture. The images were retrospectively reviewed. They were initially misinterpreted because there was extravasated contrast agent posterior to the bladder. However, on sagittal MPR images, the extravasated contrast agent was confined to the extraperitoneal space because all the contrast agent was underneath the peritoneal surface (Fig. 4C). Another difficult case showed extravasated contrast agent in the intraperitoneal space, and a small amount of fluid lateral to the bladder that was not opacified on the CT cystogram (Figs. 5A and 5B). The finding was interpreted as intraperitoneal rupture with a probable extraperitoneal rupture component. Bladder exploration showed a large defect in the bladder dome involving the peritoneal reflection and confirmed the combined intraperitoneal and extraperitoneal rupture.
Our investigation also showed that better delineation of the site of the bladder rupture can be achieved with the use of MPR. The site of the bladder rupture was identified in 14 of 18 patients in axial images. In the remaining four cases of intraperitoneal rupture, the sites of rupture were at the bladder domes, which were parallel to the scanning plane of the axial scan. They were only detected by either coronal or sagittal images in MPR. One intraperitoneal bladder rupture with laceration at the dome could be identified on the axial image (Figs. 2A, 2B, and 2C). We think this was related to the large size of the laceration because the intraoperative finding of the laceration was 5 cm.
Our investigation had several limitations. There was no comparative study to prove the accuracy of CT cystography. The results were obtained retrospectively from medical records, and therefore small extraperitoneal bladder ruptures may be missed on CT cystography and regarded as negative cases. Similarly, only nine of 18 patients with positive CT cystography results had surgical proof of bladder rupture. The exact site of injury of the bladder rupture in the remaining nine patients (two died and the remaining seven were diagnosed as having extraperitoneal rupture) could not be compared because bladder exploration was not performed in these patients.
CT cystography, however, has several pitfalls that may lead to false-negative results. The Foley catheter tip may abut the small tear site, which may occlude the contrast extravasation. The presence of pelvic hematoma may result in incomplete bladder distention. In addition, the diagnosis of combined intraperitoneal and extraperitoneal rupture may be missed if the rupture site is large because full bladder distention cannot be achieved, and most of the contrast agent is extravasated into the extraperitoneal component but not into the intraperitoneal component [11].
In conclusion, we recommend the use of CT cystography in the evaluation of patients with suspected bladder rupture. Additional sagittal and coronal images from MPR may be highly informative for identification of the site of the bladder rupture, particularly in intraperitoneal rupture when the site of perforation is at the bladder dome, which may be difficult to detect on axial images.
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