Technique and radiation

No specific patient preparation is required, although non-trauma patients must be asked to void before commencement of study. The main absolute contraindication to cystography is a UTI. Most children will receive antibiotic prophylaxis, although this is not routinely indicated in adults. In a patient with pelvic trauma, the integrity of the urethra must first be ascertained (using a retrograde urethrogram) prior to urethral catheteriza-tion. In such situations, cystography may still be carried out if safe suprapubic puncture of the bladder is possible.

• After a preliminary KUB, the bladder is catheterized

• Any water-soluble 150-strength contrast media can be used

• AP films must include bony landmarks (sacrum and symphysis pubis) to determine bladder neck descent

• In addition, 45° oblique and lateral views (with and without straining) should be taken, although this may not be possible in the pelvic trauma patient

Suspected bladder trauma

Ideally, a three-phase technique should be employed:

1. An initial 50 mL of contrast may demonstrate bladder rupture and no further contrast is required

2. If no abnormality is detected, a further 300 mL of contrast is instilled using a intravenous drip infusion giving set to adequately distend the bladder. Any significant breach of the bladder wall should become apparent

3. If cystogram remains normal, the bladder is emptied via the catheter and contrast extravasation from a small posterior tear may become obvious

Cystography following bladder surgery or for suspected vesical fistula

Typically up to 200 mL of contrast is instilled in the bladder of patients who have undergone open bladder/prostate surgery, 10-14 days post-operation. Evaluation of a fistula requires larger volumes of contrast (200-300 mL). Multiple-angle films can be obtained.

Micturating cystourethrography (MCUG)

MCUG is primarily performed in children with recurrent UTI suspected to have vesicoureteric reflux (VUR). MCUG also allows evaluation of the male (for urethral valves) and female (for ure-thral diverticula) urethra in pediatric patients.

• Residual urine is drained, recorded, and discarded

• Contrast can then be instilled via a giving set, under fluoro-scopic control so any abnormal bladder activity or reflux can be identified

• Once the bladder is full, the catheter is removed and the patient encouraged to void under fluoroscopic visualization of the entire urinary tract

• Adults and older children can be placed in a vertical position to void into a container

• Smaller children and infants are encouraged to void lying down into an absorbent pad

• Suprapubic compression may be required for infants and neuropathic bladders to attain satisfactory elevation in the intravesical pressure for reflux to occur

• A final spot film of the bladder will help determine post-micturition residual volume

Modifications

A similar study can be performed using 99mTc-pertechnetate instilled into the bladder for the diagnosis of VUR in children. Gamma camera detection of radioactivity is carried out throughout the study. The main advantage is the significantly reduced radiation dose to the patient, but this is at the expense of anatomical detail.

Recent reports have demonstrated a superior rate of bladder trauma detection using CT cystogram. Following instillation of 300-350 mL of contrast, CT scanning can be performed with a full and then empty bladder. This is an attractive option if the trauma patient is already on the CT scan table for suspected other abdominal trauma, and does not need to be transferred to another room.

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