First and second year — the floor first, then every step
A passively filled bladder on a trauma CT cannot exclude rupture: fill it retrogradely (CT cystography) and classify the leak as intraperitoneal or extraperitoneal; if the urethra may be injured, prove it is intact before a catheter goes in.
Orient first
Intraperitoneal rupture is a dome tear from a blow to a full bladder — contrast outlines bowel loops and the paracolic gutters. Extraperitoneal rupture follows pelvic fractures — contrast streaks into the perivesical fat and can track into the thigh, scrotum or abdominal wall.
The posterior urethra is injured with pelvic ring disruption (especially with symphyseal diastasis); the anterior (bulbar) urethra by straddle injuries.
Blood at the meatus, a high-riding prostate or inability to void with a pelvic fracture means: retrograde urethrogram before any catheter.
Acquire the study
CT CYSTOGRAPHY: through a catheter, instil at least 300–350 mL of dilute contrast (about 2–5% iodinated contrast) by gravity, clamp, and scan the pelvis; add post-drainage images if a leak is equivocal — verify concentration and volume against the local protocol.
Thin slices with coronal and sagittal reformats.
The manoeuvre
Axial and coronal: contrast outlining bowel loops, in the paracolic gutters and in the pouch of Douglas or rectovesical pouch → intraperitoneal.
Flame-shaped or streaky contrast in the perivesical fat and space of Retzius → extraperitoneal; follow it to the thigh, scrotum, perineum or anterior abdominal wall (complex).
The bladder wall: the site of the defect, and bone fragments projecting into it.
Both may coexist — search the whole peritoneal cavity AND the extraperitoneal pelvis on every series.
Bone window: the pelvic ring and the pubic symphysis; soft-tissue window: perivesical haematoma displacing the bladder (the "teardrop" bladder).
What confirms it
Extraluminal contrast after adequate retrograde filling, classified by where it goes.
What licenses you to exclude it
A negative study requires adequate retrograde distension (at least 300–350 mL in an adult); a passively filled bladder on the excretory phase excludes nothing.
The classic misread
Calling a bladder intact on an under-filled or passively filled study.
Missing a combined intraperitoneal and extraperitoneal rupture.
Reporting the injury
Classification to use
Bladder: intraperitoneal / extraperitoneal (simple — confined to the perivesical space; complex — tracking into the thigh, scrotum, perineum or abdominal wall) / combined; bladder contusion. AAST bladder scale may be added.
Urethra: Goldman classification (I stretch — IV/V anterior/bladder-neck patterns); or partial versus complete, anterior versus posterior.
Measurements — and how to take them
Volume of contrast instilled (mL); defect size where seen.
What to report
Filling method and volume; the rupture type and site; the extent of extravasation.
Bone fragments in the bladder; pelvic ring pattern; urethral status if assessed.
How to report it
CT: "CT cystography after retrograde instillation of 350 mL of dilute contrast: contrast outlines small bowel loops and fills both paracolic gutters from a defect at the bladder dome — intraperitoneal bladder rupture. No extraperitoneal leak."
Fluoroscopy: "Retrograde urethrogram: extravasation at the membranous urethra with no contrast entering the bladder — complete posterior urethral disruption."
What not to report
Do not report "no bladder injury" on a passively filled trauma CT.
Do not call venous intravasation a urethral tear.
Associated injuries to look for
Pelvic ring fractures (especially anterior ring and symphyseal diastasis), rectal injury, vaginal injury in women.
What changes management
Intraperitoneal rupture — surgical repair.
Simple extraperitoneal rupture — usually catheter drainage; bone fragments in the bladder, bladder neck involvement or concurrent pelvic fixation often lead to repair.
Urethral disruption — suprapubic catheter; no urethral catheter.
Reference values
Each value carries the caveat that keeps it from being misused. Normal limits and diagnostic criteria are kept apart on purpose: a disease cut-off read as a normal range is the more dangerous mistake.
Normal limits
Urinary bladder · Wall thickness by distension state
up to 3 mm well distended; up to 5 mm when nearly empty
Wall thickness is meaningless without stating the distension — an empty bladder has a thick wall and is normal. Diffuse thickening with trabeculation suggests chronic outlet obstruction; focal thickening needs cystoscopic correlation.
USG · CT
See it on real cases
Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.