Procedures · Fluoro and special studies2 min read5-question check
Cystography and urinary studies
Contrast enters the bladder by catheter and gravity, never by force. Angle 10 to 15 degrees caudad for the AP.
Retrograde cystogram
A retrograde cystogram fills the bladder through a urinary catheter. The patient voids first, the bladder is catheterized with sterile technique, and dilute iodinated contrast flows in by gravity. It is never injected under pressure, which could rupture an injured bladder. Because the contrast is not given IV, reactions are rare, but ask about allergies. Common reasons are bladder injury after pelvic trauma, leaks and fistulas. IV urography was removed from the 2027 specifications, so focus on these direct studies.
Positions
The AP uses a 10 to 15 degree caudal angle, entering about 2 inches above the pubic symphysis, so the pubic bones project below the bladder base. Posterior obliques use 45 to 60 degrees of rotation, centered 2 inches above the symphysis and 2 inches medial to the upside ASIS. A lateral may be added. Use a 40-inch SID and suspend on expiration.
VCUG and urethrogram
A voiding cystourethrogram, or VCUG, fills the bladder, removes the catheter, and images while the patient voids. It shows vesicoureteral reflux and the urethra, often in children with urinary tract infections. A male voids in about a 30 degree RPO so the urethra projects over soft tissue, not bone. A female voids AP. A retrograde urethrogram, usually in males, injects contrast into the distal urethra, imaged in a 30 to 40 degree oblique. Worked example: a man with a pelvic fracture has blood at the urinary opening. A urethrogram comes before any catheter, because a catheter could worsen a torn urethra.
Nephrostomy checks
A nephrostomy tube runs through the skin into the renal pelvis to drain an obstructed kidney. A nephrostogram injects contrast through the tube under fluoroscopy to check position, patency and leaks. The contrast moves antegrade, in the normal direction of urine flow. The patient is often prone, as during placement. Keep connections clean, collimate to the kidney and tube, and record the contrast and fluoro time.
Clinical Example
After a car crash, a CT shows a pelvic fracture and possible bladder injury. A catheter is placed after urethral injury is ruled out, and contrast runs in by gravity. You take an AP with 15 degrees caudad, both obliques, and a drainage image, which shows contrast leaking outside the bladder.
Common Mistakes
- Angling cephalad for the AP cystogram, which projects the pubic bones over the bladder base.
- Injecting contrast into the bladder under pressure instead of letting it flow by gravity.
- Placing a Foley catheter before a urethrogram when urethral injury is suspected.
- Teaching IV urography as current tested content.
Why It Matters
The registry tests the CR angle, oblique rotation, contrast route and the order of studies in trauma. Getting the order wrong can cause real harm.
Key Relationships
- AP cystogram → 10 to 15 degrees caudad, 2 inches above the symphysis
- Cystogram obliques → 45 to 60 degree posterior obliques
- Male VCUG → about 30 degree RPO
- Blood at the meatus → urethrogram before catheter
- Nephrostogram → contrast through the tube, antegrade