Radiography: intravenous urography

• Organic iodine contrast media is injected intravenously and excreted through kidneys.
• Allows visualization of urinary tract anatomy and limited assessment of urinary tract function.

• Investigation of:
  • Urinary incontinence Urinary incontinence.
  • Anuria.
  • Hematuria or pyuria not arising from the lower urogenital tract.
  • Suspect urinary bladder disease when bladder cannot be catheterized.
  • Abnormal renal size  and shape and position.
  • Retroperitoneal swellings.
  • 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 Urethral catheterization: female if looking for ectopic ureters which may be difficult for inexperienced operators in some bitches.

• 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 Enema 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 dependent upon skill of radiographer.
• May require retrograde vaginourethrogram Radiography: vaginourethrography 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.
• technique contraindicated in dehydrated patients.
  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 labelling 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.
• Grid for examination of large dog.
• 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 General anesthesia: overview recommended to minimize reaction to contrast media.

Procedure - Standard method

• There are two accepted methods of performing and IVU:
  • High volume, drip infusion:technique which may be better for visualization of ectopic ureters.
  • Low volume, bolus infusion:technique that is preferred for examination of kidneys.

• Administer cleansing enema Enema 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

• If ectopic ureters are suspected a pneumocystogram Radiography: double contrast cystography should be performed initially to give better visualization of ureters emptying into bladder.
• If using Foley catheter for pneumocystogram move catheter cranially so bulb of catheter is not in trigone of bladder as this may hinder visualization of ureteric insertions. The bulb may also obscure ureterocele.

Step 1 - Administer contrast agent

• Position dog in dorsal recumbency.
• Connect contrast via infusion to IV 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.

• 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

• 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 minutes post-injection.
• Abdominal compression will cause better filling of ureters and renal pelvis.
  Do not use abdominal compression in shocked patients or if hydronephrosia is observed.

• 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 Radiography: vaginourethrography 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.
• Feeney D A, Thrall D E, Barber D L et al (1979) Normal canine excretory urogram - effect of dose, time and individual dog variations. Am J Vet Res 40 (11), 1596-1604 PubMed.
• Kneller S K (1974) Role of the excretory urogram in the diagnosis of renal and ureteral disease. Vet Clin North Am 4 (4), 834-861 PubMed.