Contributors: Vetstream Ltd

 Species: Canine   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading

Introduction

  • Introduction or negative or positive contrast into the urinary bladder.
  • Allows visualization of radiolucent masses, calculi, foreign bodies and assessment of bladder wall.

Uses

  • Investigation of dysuria.
  • Investigation of hematuria Hematuria.
  • Evaluation of caudal abdominal masses that may be associated with the bladder.
  • Assessment of bladder integrity following trauma.
  • Identification of position of bladder when not visible on plain films.

Advantages

  • Relatively simple procedure in most patients.
  • Non-invasive.

Alternative Techniques

Time Required

Preparation

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

Procedure

  • 30 minutes dependent largely upon skill or radiographer and cooperation of patient.

Decision Taking

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

  • Risk of air embolus with pneumocystogram if severe hematuria.
  • Risk of bladder rupture if excessive contrast inserted.

Requirements

Materials Required

Minimum equipment

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

Ideal equipment

  • Ability to process films during procedure so that repeat radiographs can be made during course of study if required.
  • High output x-ray machine.
  • High definition screen.
  • Grid for examination of large dog.

Minimum consumables

  • Radiographic film and cassette.
  • Contrast agent - air, CO2, N2O, water soluble contrast.
  • Urinary catheter.
  • Sterile water-soluble lubricant (KY jelly).
  • Three way tap.

Preparation

Dietary Preparation

  • Starve animal for 12 hours prior to procedure to reduce fecal content in colon.

Restraint

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

Other Preparation

  • Administration of an enema Enema several hours before procedure to ensure colon empty.

Procedure

Approach

Step 1 - Plain radiographs

  • 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.
    • Check diagnosis not apparent on plain radiograph.

Core Procedure

 

Step 1 - Disinfect prepuce or vagina

 
  • Swab area with diluted surgical scrub.

Step 2 - Catheterize bladder

 
  • Premeasure length of urethra from plain radiograph.
  • Using sterile technique, lubricate tip of catheter with sterile lubricant (KY jelly).
  • Insert catheter into urethra Urethral catheterization: male to pre-measured length.
  • Attach three way tap.
    In females a foley catheter Urethral catheterization: female is preferable.

Step 3 - Empty bladder

 
  • Empty bladder of urine using syringe.
  • Measure volume of urine removed.

Exit

 

Step 1 - Instill contrast

 
  • Attach syringe filled with contrast to three way tap.
  • Inject contrast slowly.
  • The volume of contrast injected should usually be the same as the volume of urine removed.
  • It may be possible to palpate the bladder through the body wall in which case inject until bladder feels tense.
  • Stop injection if resistance to injection is felt or until contrast leaks round the catheter.
  • If in doubt as to degree of bladder filling, take radiograph to assess bladder filling.
    If using a foley catheter be careful not to overinflate bladder.

Step 2 - Take radiograph

 
  • Lateral and oblique left and right lateral projections should be taken.
  • Oblique projections reduce superimposition of spine on bladder.
  • Assess degree of bladder filling.
  • Bladder needs to be moderately distended to evaluate blader wall thickness.
    If bladder under filled erroneous diagnosis of bladder wall thickening may be made.
  • If bladder under filled inject more contrast and repeat radiographs.

Step 3 - Empty bladder

 
  • Re-attach syringe to three way tap and remove contrast.
  • Remove catheter.

Aftercare

Outcomes

Complications



Fatal air embolus
  • Reported following pneumocystography.
  • Rare and most likely if severe hematuria.
    It may be safer to use positive contrast or CO2 or N2O as they are more soluble in serum than air.
Bladder rupture
  • Can occur if overinflate with contrast.
    Minimize risk by measuring volume of contrast injected and stop if resistance to injection felt.
  • If suspecting bladder rupture, eg post RTA, use positive contrast.
  • Sharp pointed catheters may penetrate bladder wall if inserted too far.
Knotting or kinking of catheter
  • May occur if catheter is inserted too far.
  • Will require cystotomy to remove.
    Pre-measure length of urethra from control film to avoid this complication.

Reasons for Treatment Failure

  • Inability to catheterize bladder.
  • Misdiagnosis of bladder wall thickening if insufficient contrast injected.
  • May have mucosal abnormalities which may not be apparent on radiography.
  • Overinflation of bladder may result in false negative diagnosis.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Watters J A (1980) Urinary tract radiography - bladder and urethra. Comp Cont Ed 2, 124-134.