Micturating cystourethrogram (MCUG), is a technique for watching a person’s urethra and urinary bladder while the person urinates . The technique consists of catheterizing the person in order to fill the bladder with
a radiopaque liquid. Under fluoroscopy (real time x-rays) the radiologist watches the contrast enter the bladder and looks at the anatomy of the patient. If the contrast moves into the ureters and back into the kidneys, the radiologist makes the diagnosis of vesicoureteral reflux, and gives the degree of severity a score. The exam ends when the person voids on the table while the radiologist is watching under fluoroscopy. Consumption of fluid promotes exertion of contrast media after the procedure. It is important to watch the contrast during voiding, because this is when the bladder has the most pressure, and it is most likely this is when reflux will occur.
Indications :
1) vesicoureteric reflux.
2) study of urethra during micturition. ( fistula or stricture )
3) abnormalities of the bladder.
4) stress incontinence.
Contraindications : acute urinary tract infection.
Contrast medium : HOCM or LOCM 150.
(Low strength (approx 25% weight/volume) contrast agent i.e. Hypaque 25% urografin 150.)
Preparation of contrast :
The estimated volume of contrast medium to be given during the examination is determined mainly by the age of the child except for children less than one year of age in whom it is determined by weight:
1. Children –>
Less than one year,
Weight (kg) × 7 = capacity (ml)
Less than two years,
(2 × age in years + 2) × 30 = capacity (ml)
More than two years,
(Age in years/2 + 6) × 30 = capacity (ml)
2. Adult à 150ml contrast + 300 NS = 450 ml.
Contrast medium is given by hand injection slowly to prevent transmucosal absorption and consequent contrast reactions. It should be noted that contrast maybe also given via the gravity drip method.
Eqiupment :
1. Fluoroscopy unit with spot film device and tilting table.
2. Video recorder.
3. Catheterisation pack – and aseptic procedure pack.
4. Sterile towels.
5. Skin prep./ wash.
6. Sterile lubricant.
7. Foley catheters 5 -7 gauge French in infants larger in adults.
8. Selection of Drip stand.
Patient prep : The patient micturates prior to the examination.
Prelim film : Coned view of the bladder using the undercouch tube.
Technique :
1. The indication is almost exclusively confined to children.
2. The patient lies supine on the x-ray table.
3. Catheterise patient if patient still not catheterized.
4. The contrast media warmed to body temperature is slowly infused through the catheter using a “giving set” into the bladder.
5. Intermittent pulsed fluoroscopy is used to check the filling and for reflux up the ureters.
6. Older children and adults are given a urine receiver but smaller children should be allowed to micturate onto absorbent pads.
7. Adults will find it easier to micturate while standing erect.
Important views
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Description
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| Full bladder view ( AP )
|
The excepted bladder capacity in ml for children is calculated with the formula mentioned earlier. This view is to document the bladder wall appearances at bladder capacity. |
| Voiding urethral view
|
In boys, it should be obtained by turning him to the right or left anterior oblique position while in girls, the view is obtained in supine position. Taking this view with the catheter in may mask the appearances of posterior urethral valve (PUV). Obtaining urethral-free image in boys is unnecessary unless there is significant diagnostic doubt as to the presence of valves on the “catheter-in” image. |
| Full length view
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to demonstrate any reflux of contrast medium that might have occurred unnoticed into the kidneys and to record the post-void residue. |
An alternative to spot films is to video tape the fluoroscopy.
1) Spot films are taken of the bladder, kidneys and ureters to record the normal or abnormal anatomy.
2) When the bladder is considered full or the contrast leaks round the catheter the balloon is deflated and the catheter withdrawn. Depending on the age,the patient is asked to micturate into a receiver either erect or supine.
3) Spot films are taken during micturition and any reflux recorded.
a) The patient is rotated into the 30 degree left and right anterior obliques to demonstrate the bladder ureteric junctions.
b) To demonstrate the male urethra the left anterior oblique position is adopted with flexion of the right hip and knee to visualise the whole of the male urethra.
4) A final full length abdominal film is taken to visualise the kidneys.
Variations
For stress incontinence the film series is taken to include , at rest, straining and micturating in the lateral position, some centres have special sitting fluoro arrangements.
For fistulae and bladder tract abnormalities a series of films in AP. lateral and oblique positions may be required.
Complications :
A) Due to catheterization :
1.Temporary dysuria, frequency of micturition and acute urinary retention which occur within 24H. These effects can be minimized by encouraging the child to take more fluids and to micturate in a warm bath.
2.Transient hematuria.
3. Bladder perforation is rare.
B) Acute urinary tract infection–> can be covered by antibiotics.
C) Adverse reaction of contrast.
Evaluation of the Image
1)ID and anatomical markers must be present and correct in the appropriate area of the film.
2)Optimal exposure should penetrate all the bone structures and contrast should be low enough to visualise fully the bone and soft tissue structures.
3) Images should be marked with contrast volume and indications of voiding or straining.
Additional modalities:
Ultrasound is a useful adjunct.
Reference :
- A Guide to Radiological Procedures, Stephen Chapman, Richard Nakielny.
- http://www.e-radiography.net/technique/technique1.htm
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