Radiography: double contrast cystography

• 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.

Advantages

• Relatively simple procedure in most patients.
• Non-invasive.
• Improved mucosal detail over pneumocystogram or positive contrast cystogram.
• Enables identification of radiolucent foreign body or blood clots.

Disadvantages

• 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 Urethral catheterization: female which may be difficult for inexperienced operator in some bitches.

• Bladder ultrasonography.
• Pneumocystogram.
• Positive contrast cystography.
• Intravenous urography Radiography: intravenous urography.

Preparation

• Dependent upon method of restraint.
• If chemical restraint (GA or sedation) required, about 5 min to gather equipment.

Procedure

• 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?

Risk assessment

• 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.

Minimum equipment

• X-ray machine.
• Processing facilities.
• Protective clothing (lead apron) for radiographer.
• Positioning aids (sandbags and ties).
• Method of labelling film.

Ideal equipment

• 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.
• Grid for examination of large dog.
• Receptacle for collecting drained urine.
• Method of measuring volume of urine removed.
• Vaginal speculum if radiographing bitch.
• Sterile procedure to prevent contamination of patients urinary tract.

Minimum consumables

• Radiographic film and cassette.
• Positive contrast agent (organic iodine 370 mg/ml).
• Negative contrast agent (air if no other available).
• Urinary catheter (preferably Foley catheter).
• Three-way stopcock.
• Syringe.
• Solution for cleaning external genitalia.
• Disposable glove.

Ideal consumables

• Water soluble, sterile lubricant (KY jelly).
• Carbon dioxide or nitrous oxide for negative contrast.

• Withhold food from animal for 12 hours prior to procedure.

• Sedation is advised to facilitate restraint in all radiographic procedures.
• Some animals may require general anesthesia General anesthesia: overview.

• Administration of an enema Enema 2-3 hours before procedure to ensure colon empty.

Step 1 - Control films

• Plain abdominal radiographs Radiography: abdomen 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

• Pass male urinary catheter through urethra into bladder in dog or Foley catheter in bitch.
  May require vaginal speculum if catheterizing bitch.
• 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 installing a small volume (0.5-2 ml) of local anesthetic such as lidocaine.

Step 2 - Instill positive contrast

• Inject 5-15 ml (depending on size of dog) of water soluble positive contrast media (Urografin 150) through 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 to 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 contast 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 Radiography: vaginourethrography may be performed.

Step 3 - Remove catheter

• Remove air from bladder.
• Withdraw catheter.

Antimicrobial therapy

• Antibiotic therapy should not be required provided sterile technique used.

Potential complications

• Fatal air embolus has occured following pneumocystography.
  Incidence is higher with gas introduced while patient is in light lateral recumbancy
• Catheters with sharp points may penetrate bladder wall.
• Kinking or knotting of male urinary catheters may occur if catheter advanced too far into bladder and can require cystotomy to remove.
• Iatrogenic bacterial contamination of bladder.

• Inability to pass urethral catheter may indicate presence of urethral pathology - repeated catheterization failure requires further investigation.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Weichselbaum R C, Feeney D A, Jessen C R et al (1999) Urocystolith detection: comparison of survey, contrast radiographic and ultrasonographic techniques in an in vitro bladder phantom. Vet Radiol Ultrasound 40 (4), 386-400 PubMed.
• Weichselbaum R C, Feeney D A, Jessen C R et al (1998) In vitro evaluation of contrast medium concentration and depth effects on the radiographic appearance of specific canine urolith mineral types. Vet Radiol Ultrasound 39 (5), 396-411 PubMed.
• Scrivani P V, Léveillé R, Collins R L (1997) The effect of patient positioning on mural filling defects during double contrast cystography. Vet Radiol Ultrasound 38 (5), 355-359 PubMed.
• Mahaffey M B, Barsanti J A, Crowell W A et al (1989) Cystography - effect of technique on diagnosis of cystitis in dogs. Vet Radiol and Ultrasound 30 (6), 261-267 VetMedResource.
• Park R D (1974) Radiographic contrast studies of the lower urinary tract. Vet Clin N A 4 (4), 863-87 PubMed.