1. BLADDER INJURY: TYPES, MECHANISMS, AND DIAGNOSTIC IMAGING
Jordan S. Gross, MD; Scott Rotenberg, MD; Mindy M. Horrow, MD
Department of Radiology
Einstein Medical Center
Philadelphia, Pa
Address correspondence to: J.S.G., 5501 Old York Road, Philadelphia, PA (

2. Learning Objectives
Identify anatomic spaces and structures related to the bladder
Describe the role of computed tomography (CT) and CT cystography in imaging of bladder trauma
Define types of bladder rupture
List at least three mechanisms of bladder injury
Describe the imaging features or clues that help diagnose bladder trauma at CT cystography and noncystographic CT

3. Introduction
Bladder injury typically can be categorized as either (a) traumatic or (b) spontaneous, with most cases of traumatic injury being due to blunt or penetrating trauma.
Bladder injury may be extraperitoneal, intraperitoneal, or mixed.
Prompt diagnosis and appropriate management lead to reduced morbidity and mortality.
Serious complications usually are associated with a delay in diagnosis and/or treatment.

4. Normal Male Anatomy
Perivesical space: surrounds and con-tains the urinary bladder, medial um-bilical ligaments (obliterated umbilical arteries), and median umbilical liga-ment (urachus); is analogous to the perinephric space
Rectovesical pouch: intraperitoneal space between the rectum and the urinary bladder
Presacral space
Prevesical space (Retzius space): continuous with presacral space and the fat surrounding the obturator muscle and external iliac vessels; separated from the perivesical space by the umbilicovesical fascia**
**Umbilicovesical fascia: extends between the medial umbilical ligaments from the umbilicus inferiorly to the urinary bladder, becoming continuous with the visceral fascia of that organ

5. Normal Female Anatomy Medial umbilical ligaments
Perivesical space: bordered by the medial umbilical ligaments (obliterated umbilical arteries); surrounds and contains the urinary bladder and median umbilical ligament (urachus); analogous to perinephric space
Rectouterine pouch (Douglas pouch): extension of the peritoneum between the rectum and the back wall of the uterus; analogous to the rectovesical pouch in males
Peritoneal space
Presacral space
Prevesical space (Retzius space): continuous with presacral space and the fat surrounding the obturator muscle and external iliac vessels; separated from the perivesical space by the umbilicovesical fascia

6. Diagnostic Imaging: CT Cystography
Has replaced conventional cystography as the study of choice for bladder trauma
Advantages:
CT study of abdomen and pelvis is often ordered for patients with abdominal trauma
Allows review of multiplanar reformatted images
Important in intraperitoneal bladder ruptures, when damage at bladder dome may be difficult to visualize in the axial plane
Studies have shown CT cystography is at least as accurate as conventional cystography (Deck et al, 2000)

7. CT Cystography: Indications and Technique
1. Conventional CT findings of pelvic fractures, hematoma, indistinct bladder wall
2. Mechanism of trauma that leads to high suspicion for bladder trauma
Technique:
1. Preinjection imaging of the pelvis
2. Preparation of 500 mL of dilute contrast solution
3. Instillation of 350–400 mL of the contrast solution under gravity flow via a Foley catheter
4. Clamp the Foley catheter to maintain bladder distention

8. Extraperitoneal Bladder Rupture
Most common form of bladder injury (80%–90% of cases)
Often results from pelvic fracture with direct perforation of the bladder wall
Causes separation of fascial planes between the bladder and pelvis
Imaging sign: Relatively contained extravasated fluid that remains isoattenuating relative to the attenuation of fluid in the bladder
Can be simple or complex
Simple: Extravasated contrast solution is limited to perivesical space
Complex: Extravasated contrast solution extends to thigh, scrotum, perineum
Treatment: Most often, urinary drainage via Foley catheter; more severe injury may require surgery

9. Simple Extraperitoneal
Bladder Rupture
Axial images from CT cystography show extravasation of contrast solution into the perivesical space.

10. Axial images from CT cystography show an accumulation of extravasated contrast solution in the form of the crown of a molar tooth, an indication of a simple extraperitoneal bladder rupture. The crown of the molar tooth lies anterior to the bladder, and its root extends laterally.

11. Complex Extraperitoneal
Bladder Rupture
Axial images from CT cystography show extravasation of contrast solution into the perivesical space and beyond it, to the prevesical space, scrotum, and thigh.

12. Defect at the level of the bladder neck
Defect at bladder neck
Axial (top left) and sagittal (top right) images from CT cystography and fluoro-scopic image from conventional cystog-raphy (bottom) show extravasation of contrast solution into nearby soft tissues from a defect (arrow) at the bladder neck. Although most extraperitoneal bladder ruptures are managed with drainage via Foley catheter, surgery may be needed to repair a tear at the bladder neck.

13. Intraperitoneal Bladder Rupture
Less common than extraperitoneal bladder rupture (only 10%–20% of cases are intraperitoneal)
Secondary to injury of bladder dome
Communication between bladder and peritoneal cavity
Extravasated contrast solution may be seen in:
Paracolic gutters
Rectovesical/rectouterine pouch
Surrounding bowel loops
Extravasated contrast solution often appears less concentrated relative to contrast solution in the bladder
Since the intraperitoneal space is large, more urine may extravasate and small amounts of extravasated contrast solution will be diluted
Treatment: Most often, surgical intervention

14. Intraperitoneal Bladder Rupture
Axial images from CT cystography show extravasated contrast solution outlining multiple bowel loops in the intraperitoneal space.

15. Intra- and Extraperitoneal (Mixed) Bladder Rupture
Extravasated contrast solution in the extraperitoneal space is more concentrated than that in the intra-peritoneal space.

16. Location, Location, Location …
The location of the tear, slightly lateral to the dome of the bladder in this coronal view, is suggestive of an extra-peritoneal bladder rupture.
Extravasated contrast solution confined to the prevesical space is suggestive of a simple extraperitoneal bladder tear. No intraperitoneal component is seen on this image.

17. Mechanisms of Traumatic Bladder Injury: Blunt or Penetrating Force
Blunt trauma is the reported cause in 67%–86% of cases of bladder injury due to external trauma.
The degree of bladder distention at the time of impact is correlated with the degree of injury.
Bladder rupture due to blunt trauma is often associated with pelvic fractures.
Penetrating trauma is the reported cause in 14%–33% of cases of bladder injury due to external trauma.

18. Left pubic bone fracture
Diastasis of pubic symphysis
Complex extraperitoneal bladder rupture associated with multiple pelvic fractures in a male patient with blunt trauma due to a motorcycle accident. Injuries to pubic bone were seen on initial CT images (top left and right), with extravasated contrast solution on the follow-up CT cystogram (bottom).

19. Injury to the bladder dome
Multiplanar reformatted images from postoperative CT cystography in the same patient show contrast solution extravasa-ting from the bladder dome (top right) and surrounding the bowel loops (bottom left), findings indicative of an intraperi-toneal bladder rupture. (Air bubbles are from an open surgical incision.) A malposi-tioned Foley catheter in the prostatic urethra also is incidentally seen (arrow, bottom right).
Injury to the bladder dome

20. Bladder Rupture Due to Penetrating Trauma
Axial and coronal images from CT cystography in a patient with an extraperitoneal bladder rupture due to penetrating trauma show extravasated contrast solution in the prevesical space (Retzius space), a hematoma within the bladder, and multiple foci of gas in soft tissues lateral to the iliac bone.

21. Mechanisms of Spontaneous Bladder Injury
Spontaneous bladder perforation is much less common than traumatic bladder perforation.
Spontaneous perforation is due to an increase in bladder pressure and weakening of bladder mucosa.
Possible causes of spontaneous perforation include urinary tract infection, urinary retention, vaginal delivery, alcoholism, bladder stones, radiation therapy, and Foley catheter malposition.

22. Mechanisms of Iatrogenic Bladder Injury
Iatrogenic bladder perforation may occur with:
Surgery of the prostate, bladder, or other nearby structures
Cystoscopy (with or without bladder biopsy)
Manipulation of a ureteral stent, Foley catheter, or suprapubic catheter
Many iatrogenic bladder perforations are clinically unsuspected and thus may be detected only in noncystographic imaging studies

23. Iatrogenic Bladder Rupture: Causes and Imaging Appearances
Prevesical
space
Perivesical space
Presacral space
Axial images from CT cystography show extraperitoneal bladder rupture in two different patients after bladder surgery (left) and after cystoscopy (right). Note the bladder diverticula, which may distract the eye from the key diagnostic findings.

24. Bladder Rupture: Clues at Noncystographic CT
Unusual fluid collections
Unusual gas collections
Abnormal location of a Foley catheter
Defect in an enhancing bladder wall
Use of coronal and sagittal reformatted images may be helpful to confirm the diagnosis.

25. Bladder Injuries Detected at Noncystographic Imaging: Four Case Studies

26. Case 1. Initial axial CT images obtained in a 51-year-old man with trauma from a fall (top left and right) show a defect in the enhancing bladder wall (arrow).
Follow-up CT cystogram (bottom left) shows extravasated contrast solution in the perivesical space (arrow), helping confirm the presence of a simple extraperitoneal bladder rupture.

27. Case 2. Axial unenhanced CT images obtained at progressively lower levels (left to right, top to bottom) in the abdomen and pelvis of a 49-year-old woman after placement of a Foley catheter …
Bladder
Foley balloon
Foley balloon
… show the Foley balloon apparently in a normal position within the bladder. (Case continues.)

28. Case 2 (continued). Unexpected collections of ascitic fluid and free air in the patient’s upper abdomen, seen in the same CT study, are suggestive of iatrogenic bladder perforation. The fluid presumably was urinary ascites. (Case continues.)
Free air
Free air
Ascites

29. Case 2 (continued). Coronal (left) and sagittal (right) reformatted images from intravenous contrast material–enhanced CT depict a malpositioned Foley balloon (arrow) superior to the bladder (B). (Case continues.) B B

30. Case 2 (continued). Conventional cystography, performed the next day, helped confirm the presence of an intraperitoneal bladder tear …
… and allowed localization of the site of injury at the dome of the bladder.
Extraluminal contrast solution seen within the peritoneum helps identify the bladder injury as intraperitoneal.

31. Case 3. Axial images from unenhanced CT in a 61-year-old man with rebound tenderness soon after cystoscopy show unusual air and fluid collections that are probably located in both intra- and extraperitoneal spaces. (Case continues.)

32. Case 3 (continued). Repeat CT cystography shows extra-vasated contrast solution in both extraperitoneal and intraperitoneal spaces, findings indicative of a mixed bladder rupture. Note that the contrast material in the intraperi-toneal space is less concentrated than that in the extraperi-toneal space.

33. Case 4. Ultrasonography in a 56-year-old man after a suprapubic cystostomy and Foley catheter placement shows the catheter balloon (white arrow) outside the confines of the urinary bladder (B). B
Unenhanced CT scans show air and fluid in the prevesical space (Retzius space) and hematoma within and outside the bladder.

34. Quiz: Case 1, Question 1
This conventional cystogram was obtained emergently in a patient with pelvic trauma. What type of bladder tear is indicated?
Intraperitoneal, because the perforation is localized to the bladder dome

35. Quiz: Case 1, Question 2
What type of bladder rupture is seen on the follow-up CT cystogram? What features are indicative?
The CT cystogram helps confirm a mixed intra- and extraperitoneal bladder rupture.
The molar tooth–shaped region of extravasated contrast solution indi-cates the presence of an extraperi-toneal component.
Contrast solution outlining multiple bowel loops is indicative of an intraperitoneal bladder rupture.

36. Quiz: Case 2
What findings on these noncystographic CT images are suggestive of a mixed intra- and extraperitoneal bladder rupture in this patient who presented with hematuria after radiation therapy?
Unusual collections of air and fluid (white arrows) outside the bladder
Defect (black arrow) in the enhancing bladder wall

37. Teaching Points
In patients with suspected bladder injury due to trauma, even if the findings at initial CT are negative, cystography (CT or conventional) must be performed to rule out a bladder tear.
CT cystography allows accurate diagnosis of the type of bladder rupture, including complex extraperitoneal and mixed intra- and extraperitoneal tears.
Iatrogenic bladder ruptures may be clinically occult and detected only on the basis of subtle or indirect findings at CT, or occasionally, ultrasonography.
Spontaneous bladder rupture occasionally occurs in patients with an infection, an indwelling Foley catheter, or a history of radiation therapy.

38. Suggested Readings
Almgren B, Bergqvist D, Hedelin H. Intraperitoneal bladder perforation caused by an indwelling Foley catheter. Scand J Urol Nephrol 1977; 11: 297–299. Chan DP, Abujudeh HH, Cushing GL, and Novelline RA. CT cystography with multiplanar reformation for suspected bladder rupture: experience in 234 cases. AJR Am J Roentgenol 2006; 187: 1296–1302. Deck AJ, Shaves S, Talner L, et al. Computerized tomography cystography for the diagnosis of traumatic bladder rupture. J Urol 2000; 164: 43–46. Korobkin M, Silverman PM, Quint LE, et al. CT of the extraperitoneal space: normal CT anatomy and fluid collections. AJR Am J Roentgenol 1992; 159: 933–941. Magee GD, Marshall SG, Wilson BD, Spence RAJ. Perforation of the urinary bladder due to prolonged use of an indwelling catheter. Ulster Med J 1991; 60: 237–239. Vaccaro JP, Brody JM. CT cystography in the evaluation of major bladder trauma. RadioGraphics 2000; 20: 1373–1381.