Radiography: intravenous urography

• Visualization of urinary tract anatomy and limited assessment of urinary tract function.

• Investigation of urinary incontinence Urinary incontinence.
• Investigation of anuria.
• Investigation of hematuria or pyuria not arising from the lower urogenital tract.
• Investigation of suspect urinary bladder disease when bladder cannot be catheterized.
• Investigation of abnormal renal size  and shape and position.
• Investigation of retroperitoneal swellings.
• Investigation of suspect ureteric disease, eg ectopic ureters  .
• Identification of kidneys when not visible on plain radiographs.

Advantages

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

Disadvantages

• General anesthesia recommended.
• Limited use in assessing renal function.
• Contraindicated if moderately or severely azotemia.
• Risk of anaphylactic or adverse reactions to contrast (rare).
• Large volume of contrast may affect cardiovascular system.

• Requires bladder catheterization Urethra: catheterization if looking for ectopic ureters which may be difficult for inexperienced operators.

• Renal ultrasonography.
• Bladder ultrasonography for detection of ectopic ureters.
  Failure to identify ureteric jet does not rule out ectopic ureters.
• Scintigraphy.

Preparation

• Dependant upon method of restraint.
• Food with held for 12-24 hours.
• Enemas required ideally night before but not within 2-3 hours of procedure.
• Renal function and hydration should be assessed prior to procedure.
• Samples for urinalysis if required should be taken prior to contrast radiography.

Procedure

• 40 min dependant upon skill of radiographer.
• May require retrograde vaginourethrogram in addition if suspect ectopic ureter Ureter: ectopic and ureters not clearly visible on IVU.

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

• Check renal function and hydration status prior to procedure.
  Care should be taken in patients with cardiac disease if high volume technique used as may   →   volume overload.

Minimum equipment

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

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.
• Cassette tunnel if performing 'low volume bolus' technique.

Minimum consumables

• Radiographic film.
• Contrast agent.
• Urinary catheter.
• Three-way stopcock.
• Syringe.
• Sterile water soluble lubricant (KY jelly).
• IV fluid infusion.

• Withhold food for 12-24 hours prior to procedure.

• General anesthesia recommended to minimize reaction to contrast media.

• Administer cleansing enema Enema the night before procedure and 2-3 hours before procedure if necessary.
• Place cephalic vein intravenous catheter Cephalic catheterization for administration of contrast agent.

Step 1 - Control Films

• Plain abdominal radiographs Radiography: abdomen (lateral and ventrodorsal) including pelvic region should be taken prior to contrast study to:
  • Check exposure settings and processing.
  • Confirm animal adequately prepared, ie colon empty.
  • Confirm positioning adequate.
  • Confirm diagnosis not apparent without contrast study.

Step 2 - Additional radiographic contrast studies

High volume technique

• If ectopic ureters are suspected a pneumocystogram Radiography: double contrast cystography should be performed initially to give better visualization of ureters emptying into bladder.

Step 1 - Administer contrast agent

High volume technique

• Position animal in dorsal recumbency.
• Connect contrast via giving set to intravenous catheter and start infusion.
• Infuse contrast over 10 min.
• Concentration of contrast is 150 mg I/ml (Urografin 150).
• Dose of contrast approximately 5-10 ml/kg.

Low volume bolus technique

• Rapid injection of more concentrated contrast agent, eg omnipaque (300-400 mg I/ml).
• Dose of contrast used 600-800 mg I/kg.
  Injection should be given as rapidly as possible.

Step 2 - Obtain radiographic views

High volume technique

• See abdominal radiography for positioning techniques Radiography: abdomen.
• Ventrodorsal abdominal projections taken at 5 min after start of infusion to visualize nephrogenic phase.
  Angiogram phase not visible with this technique.
• Lateral and ventrodorsal projections taken at 5 min intervals.
• Oblique lateral projections to identify ectopic ureter may be taken at 10-15 min post-injection.

Low volume bolus technique

• Ventrodorsal abdominal projections taken immediately on completion of injection to try to visualize angiogram phase.
• Subsequent films are taken at approximately 1, 5, 10, 15 and 20 min.
• Ventrodorsal projections should be taken at 0 and 1 min.
• Ventrodorsal, lateral and oblique projections taken subsequently once ureters become opacified.

Step 1 - Assess radiographs

• The study is complete when the kidneys, pelvic recesses and ureters have been visualized.
  Usually 25-30 min.

Step 2 - Additional radiographic projections

• Choice of projection depends on abnormality and area of interest.
• Ventrodorsal projection gives most information on kidneys whereas lateral and lateral oblique views give better visualization of terminal ureter.
• If suspect ectopic ureters a retrograde vaginourethrogram can be performed.

Potential complications

• Acute renal failure has been reported following intravenous urography.
  Suspect this if opacification of kidneys does not increase or change with time and no contrast appears in ureters.

• Poor opacification may occur if poor renal perfusion or renal disease is present.
• May be difficult to identify ectopic ureters especially if intrapelvic positioned bladder.
  Retrograde vaginourethrogram may be helpful.

Refereed papers

• Recent references from PubMed and VetMedResource.

• Feeney D A, Barber D L & Osborne C A (1982) The functional aspects of the nephrogram in excretory urography - A review. Vet Radiol 23 (2), 42-45 VetMedResource.
• Feeney D A, Barber D L, Johnson G R & Osbourne C A (1982) The excertory urethrogram - Part I techniques, normal radiographic appearance and misinterpretation. Comp Cont Ed Pract Vet 4, 233-240.

Other sources of information

• Knelle S K (1974) Role of the excretory urogram in the diagnosis of renal and ureteral disease. Vet Clin North Am 4, 834-861.