Contributors: Barbara J Watrous
Species: Canine | Classification: Techniques
- Radiography following injection of contrast into urethra.
- Allows visualization of urethra.
- Investigation of dysuria.
- Investigation of hematuria Hematuria of suspected lower urinary tract origin.
- Investigation of urinary obstruction, eg urethral calculi .
- Allows identification of patency of urethra Urethra: obstruction.
- Assessment of presence of urethral disease.
- Post-trauma, allows identification of urethal rupture Urethra: rupture.
- Investigation of urinary incontinence Urinary incontinence.
- May give information on bladder disease if unable to pass catheter due to urethral obstruction .
- Investigation of prostatic disease Prostate disease.
- May not identify functional urethral obstructions, eg urethral spasm, reflex dyssynergia.
- Ultrasonography for investigation of prostatic disease.
- 5 minutes to collect materials.
- 5 minutes.
- Usually performed before or following contrast cystography.
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?
- Deep sedation required.
- Some animals may require general anesthetic.
- X-ray machine.
- Processing facilities.
- Protective clothing (lead apron) for radiographer.
- Lead sleeves and gloves for radiologist because of exposures made during injection.
- Positioning aids (sandbags, cradle and ties).
- Method of labelling 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.
- Grid for examination of large dog.
- Radiographic film.
- Urinary catheter (can use a paediatric Foley catheter 5 F).
- Water soluble positive contrast agent.
- Atraumatic (tongue) clamp.
- Sterile water soluble lubricant (KY jelly).
- Withhold food from patient for 12 hours prior to anesthetic to prevent reflux esophagitis.
- Sedation or general anesthetic required General anesthesia: overview.
Step 1 - Control films
- Check exposure settings and processing.
- Confirm positioning adequate:
- Position in lateral recumbancy.
- Pull hind limbs cranially to avoid superimposition over urethra (flex coxofemoral joints with stifles straight).
- Check size of bladder.
- Confirm diagnosis not apparent without contrast study or with positive contrast cystogram alone.
Step 2 - Additional radiographic studies
- Perform pneumocystogram Radiography: double contrast cystography taking care bladder will not be over-distended after injection of contrast.
- The increased intravesicular pressure results in better filling of the urethra.
- Using sterile technique, lubricate tip of catheter with sterile lubricant (KY jelly).
A paediatric Foley catheter can be used which prevents backflow of contrast.
Step 1 - Catheterize urethra
- Insert catheter 1-3 cm into urethra and inflate bulb if Foley catheter used.
- Inflate bulb so that urethra lumen is occluded and catheter prevented from moving.
Take care not to over-inflate Foley catheter bulb as this may lead to pressure necrosis of urethra.
- May be necessary to insert catheter further (approximately mid-os penis) if using urinary catheter to prevent catheter moving out of urethra during contrast injection.
- Apply atraumatic clamp to end of prepuce to hold catheter in place and prevent backflow of contrast if a balloon, eg Foley catheter is used.
- If sedation is used, the procedure cause discomfort therefore 2-3 ml of local anesthetic can be injected prior to contrast.
Be careful not to over-distend catheter bulb.
Step 2 - Inject positive contrast
- Usually 3-15 ml of water soluble contrast (Renocal 75) required to distend urethra (depending on size of patient).
- May require more in some dogs.
Contast may be mixed with KY jelly to allow contrast to remain in urethra for longer, allowing exposue to be taken at end of injection.
Step 3 - Obtain radiographic views
- Expose radiograph during injection of contrast if using contrast on its own.
Radiographer should wear lead gown and sleeves.
- Exposure may be made at end of contrast injection if mixture of contrast and KY jelly is used (radiographer injects contrast and steps away). However some contraction of urethra will occur
This is preferable from a radiation safety point of view.
Step 1 - Assess radiographs
- If urethral narrowing visible the contrast radiograph should be taken to confirm presence of narrowing and not due to spasm.
The urethra is normally narrower at ischial arch.
- Air bubbles in contrast may be mistaken for calculi.
Avoid air bubbles by careful filling of syringe and prefilling of catheter with contrast.
Step 2 - Additional radiographic projections
- Repeat for left and right lateral projections if necessary.
Occasionally ventrodorsal projections may be helpful.
- If filling abnormalities visible, position catheter adjacent to abnormality to provide better filling of urethra.
Step 3 - Remove catheter
- Empty bladder of air.
- Remove catheter.
- A small amount of hematuria is common following the procedure.
- Over-distension of Foley catheter cuff may cause transient urethral inflammation.
Fatal air embolism has been reported following pneumocystography - carbon dioxide or nitrous oxide is safer.
Reasons for Treatment Failure
- May get leakage of contrast backwards if end of urethra not occluded → contrast contaminating haircoat.
- May not identify functional obstructions.
- Recent references from PubMed and VetMedResource.
- Johnston G R, Stevens J B, Jessen C R et al (1983) Complications of retrograde contrast urethrography in dogs and cats. Am J Vet Res 44 (7), 1248-1256 PubMed.
- Barsanti J A, Crowell W, Losonsky J et al (1981) Complications of bladder distention during retrograde urethrography. Am J Vet Res 42 (5), 819-821 PubMed.
- Ackerman N (1980) Use of the pediatric Foley catheter for positive-contrast retrograde urethrography. Mod Vet Pract 61 (8), 684-686 PubMed.
- Ticer J W, Spencer C P & Ackerman N (1980) Positive contrast retrograde urethrography - a useful procedure for evaluating urethral disorders in the dog. Vet Radiol 21 (1), 2-11 Wiley Online Library.
- American College of Veterinary Radiology, Dr M Bernstein, Executive Director, P.O.Box 87, Blencoe, IL 60022, USA. www.acur.ucdauis.edn.