Contributors: Barbara J Watrous
Species: Feline | Classification: Techniques
- Introduction of negative and positive contrast into bladder gives maximum radiographic information on bladder disease.
- Investigation of hematuria Hematuria.
- Investigation of dysuria.
- Identification of non-radiodense uroliths Urolithiasis .
- Assessment of bladder wall thickness.
- Assessment of bladder mucosal lining .
- Identification of bladder masses.
- Relatively simple procedure in most patients.
- Improved mucosal detail over pneumocystogram or positive contrast cystogram.
- Enables identification of radiolucent foreign body or blood clots.
- Can be impossible to catheterize some patients (with obstructed urethras).
- Risk of air embolus or bladder rupture if bladder over inflated with air or severe hematuria.
- Not appropriate if bladder or urethral rupture suspected.
- Requires bladder catheterization Urethra: catheterization which may be difficult for inexperienced operator.
- Bladder ultrasonography.
- Positive contrast cystography .
- Intravenous urography Radiography: intravenous urography.
- Dependent upon method of restraint.
- If chemical restraint (GA or sedation) required about 5 min to gather equipment.
- 30 min dependent largely upon skill of radiographer and cooperation of patient.
Criteria for choosing test
- Is the examination appropriate?
- Can you make the diagnosis without it?
- Will your management of the case be affected by the outcome of the examination?
- Samples for urinalysis should be collected prior to contrast radiography.
- If bladder or urethral rupture is suspected Bladder: trauma rupture a positive contrast study is preferred.
- X-ray machine.
- Processing facilities.
- Protective clothing (lead apron) for radiographer.
- Positioning aids (sandbags and ties).
- Method of labeling film.
- Ability to process films during procedure so that repeat radiographs can be taken during course of study if required.
- High output x-ray machine.
- High definition screen.
- Receptacle for collecting drained urine.
- Method of measuring volume of urine removed.
- Vaginal speculum if radiographing bitch.
- Sterile procedure to prevent contamination of patient's urinary tract.
- Radiographic film and cassette.
- Positive contrast agent (organic iodine 370 mg/ml solution).
- Negative contrast agent (air if no other available).
- Urinary catheter (Tom cat or preferably small Foley catheter).
- Solution for cleaning external genitalia.
- Water soluble, sterile lubricant (KY jelly).
- Carbon dioxide or nitrous oxide for negative contrast.
- Withhold food from animal for 24 hours prior to procedure.
- Sedation is advised to facilitate restraint in all radiographic procedures.
- Some animals may require general anesthesia.
- Administration of an enema (eg Micralax) 2-3 hours before procedure to ensure colon and rectum empty.
Step 1 - Control films
- Plain abdominal radiographs should always be taken prior to contrast study to:
- Check exposure settings.
- Confirm animal adequately prepared ie colon empty.
- Confirm positioning adequate.
- Identify any radiographic abnormalities that may be obscured by contrast medium.
- Premeasure length of urethra on control films to give indication of how far to advance catheter.
Step 2 - Prepare site
- Cleanse external genitalia.
Avoid iodine-based solutions as these may be visible on radiograph.
- Lubricate catheter with sterile water soluble lubricant (KY jelly).
Step 1 - Drain bladder
- Catheterize bladder Urethra: catheterization.
- Empty bladder and record volume of urine removed.
- Inflate bulb of Foley catheter with water/saline.
If animal is minimally sedate, local anesthesia of urethral and bladder mucosa can be done by instilling a small volume (0.5-2 ml) of local anesthetic such as lidocaine.
Step 2 - Instill positive contrast
- Inject 0.5-1 ml of water soluble positive contrast media (Urografin 150) through the catheter.
- Some authors advocate rolling animal through 360degrees to coat surface of bladder with contrast.
This is probably not necessary if bladder empty when contrast introduced as all of bladder mucosa will be in contact with contrast.
Step 3 - Add negative contrast
- Inflate bladder with negative contrast agent.
- Carbon dioxide and nitrous oxide are recommended as they are more soluble in serum than air, if gas embolism should inadvertently occur.
- The bladder is inflated until a volume of contrast equivalent to the volume of urine removed has been added, gas leaks around catheter, when a balloon (Foley) catheter is not used or resistance to inflation is felt.
Take care not over distend bladder.If in doubt take radiographs to assess bladder distension and add more air if necessary.
Step 4 - Obtain radiographic views
- Obtain left, right and oblique lateral abdominal Radiography: abdomen projections.
Step 1 - Assess radiographs
- If inadequate distension of bladder inject more air.
- Inadequate bladder distension with air may lead to erroneous diagnosis of bladder wall thickening and mucosa irregularity.
- Over distension may result in false negative diagnosis.
- Retrograde flow of contrast medium to ureter and renal pelvis often occurs.
Care not to misinterpret air bubbles for pathology, eg calculi.
- Normal contrast cystography does not exclude lower urinary tract disease.
Step 2 - Additional radiographic procedures
- If suspect urethral involvement a retrograde urethrogram or vaginourethrogram may be performed.
Step 3 - Remove catheter
- Remove air from bladder.
- Withdraw catheter.
- Antibiotic therapy should not be required provided sterile technique used.
- Fatal air embolus has been reported following pneumocystography.
Incidence is higher with gas introduced while patient is in right lateral recumbency.
- Catheters with sharp points may penetrate bladder wall.
- Iatrogenic bacterial contamination of bladder.
Reasons for Treatment Failure
- Inability to pass urethral catheter may indicate presence of urethral pathology - repeated catheterization failure requires further investigation.
- Recent references from PubMed and VetMedResource.
- Johnston G R, Feeney D A & Osbourne C A (1982) Urethrography and cystography in cats - 1. techniques, normal anatomy and artefacts. Comp Cont Ed Pract Vet 10, 823-836.
- Zontine W J & Andrews L K (1978) Fatal air embolization as a complication of pneumocystography in two cats. JAVRS 19 (1), 8-11 VetMedResource.
- Park R D (1974) Radiographic contrast studies of the lower urinary tract. Vet Clin North Am 4 (4), 863-87 PubMed.